An important aspect of any IoT device is how secure the device is when it communicates with other devices, gateways or the cloud. It is common for developers to secure communications such as TCP/IP connections, Bluetooth or Zigbee. However, if a microcontroller sends sensitive information over a simple interface such as a UART to another microcontroller, it is important to realize that data should also be secured to prevent someone from snooping the UART line.

Silicon Labs offers a hardware CRYPTO module that provides an efficient acceleration of common cryptographic operations and allows these to be used efficiently with low CPU overhead. In addition to the CRYPTO module, Silicon Labs also provides a mbed TLS library to integrate with mbed TLS to allow it to take advantage of the CRYPTO module acceleration.

To use mbed TLS in a Micrium OS based application, first the developer must understand how the mbed TLS library will be used in the application. By default, mbed TLS is intended to be used in a single threaded/bare metal application or used in only a single thread of an RTOS application. For a Micrium OS application, this means if there will only be one task calling mbed TLS functions then no special modifications to the config file are necessary. If mbed TLS will be called from multiple tasks, for example a Bluetooth project that has a UART to communicate to another microcontroller, then a few modifications need to be made to the mbed TLS config header.

The following instructions will show you how to enable thread protection in mbed TLS for a Micrium OS Blink project on the Giant Gecko Series 1 (SLSTK3701A). If you have any difficulty getting the project set up, a .sls file is attached to this post for you to download. If you need further information on the SiLabs’ mbed TLS library, refer to Application Node AN0955.

Open Simplicity Studio and with your GG11 plugged in, select the board under debug adapters and then expand the Software Examples. Select the SLSTK3701A_micriumos_blink project and jump to the Simplicity IDE. 

First, mbed TLS must be added to the project as its not already included. You can either download mbed TLS from https://tls.mbed.org or you can grab a copy from your install of Simplicity Studio from: Simplicity Studio install location -> Eclipse -> developer -> sdks -> gecko_sdk_suite -> v2.4 -> util -> third_party -> mbedtls. Place those files into the workspace folder for the SLSTK3701A_micriumos_blink.

Once you have mbed TLS added to the project, you need to add the SiLabs library for mbed TLS to the workspace for SLSTK3701A_micriumos_blink. Under the Simplicity Studio install you can copy the sl_crypto folder and config folder from here: Eclipse -> developer -> sdks -> gecko_sdk_suite -> v2.4 -> util -> third_party -> mbedtls.

After adding the folders to the workspace similar to the image above, include paths need to be added to the project. Under the project properties, go to C/C++ Build -> Settings -> GNU ARM C Compiler -> Includes. 

Paths need to be added for the config directory, include directory and the sl_crypto directory. After adding those paths, remain in the project settings and go to Symbols under GNU ARM C Compiler.

At this point, mbed TLS has been added to the project, but it is only set to run in its default configuration. This means it won’t take advantage of the CRYPTO module acceleration and it won’t work from multiple threads. To fix that, add a new symbol that contains the following: MBEDTLS_CONFIG_FILE="config-sl-crypto-all-acceleration.h" then click OK. This will tell all mbed TLS files to look at the new config file, rather than the default config.h file.

Open up the config-sl-crypto-all-acceleration.h under the config directory. This is the default config file for enabling all hardware accelerations supported by SiLabs’ mbed TLS library. Add the following code to the header file to enable threading and remove a requirement for network sockets (unless you plan to use them). This code must be placed directly below the #include “mbedtls/config.h”.

/* Include the default mbed TLS config file */
#include "mbedtls/config.h"

/* Add Micrium OS support */
#define MBEDTLS_THREADING_ALT
#define MBEDTLS_THREADING_C
#define MBEDTLS_MICRIUM
#undef MBEDTLS_NET_C

#undef MBEDTLS_TIMING_C

Finally, the last piece to enable Micrium OS support in mbed TLS is to initialize threading support before starting Micrium OS. In the file ex_main.c, place the following code in main() anytime after the OSInit() call and before OSStart(). This will initialize the necessary mutexes to provide the protection.

// Enable Micrium OS support
#if defined ( MBEDTLS_THREADING_C )
    THREADING_setup();
#endif

At this point, after the OSStart() call completes and multitasking has begun, any mbed TLS call can be made safely from any task in Micrium OS.

The objective of this blog is to show you the steps necessary to use an existing Micrium OS USBD example and add CDC-ACM class and demo using the EFM32GG11.

Baseline Project

Since the Gecko SDK currently ships with a ‘micriumos_usbdhidmouse’ project for the SLSTK3701A_EFM32GG11 board, we can make a copy of it and rename it ‘micriumos_usbdcdcacm’. The convenience of making a copy of the project is to modify it according to our needs without breaking the Gecko SDK default projects.

Start by locating the ‘micriumos_usbdhidmouse’ folder in your Simplicity Studio installation. The project location is at ‘C:\SiliconLabs\SimplicityStudio\v4\developer\sdks\gecko_sdk_suite\v2.4\app\mcu_example\SLSTK3701A_EFM32GG11’

Once you found the folder, make a copy of it and rename it ‘micriumos_usbdcdcacm’. Please make sure to keep the new folder at the same path location of the original.

Locate the ‘SLSTK3701A_micriumos_usbdhidmouse.slsproj’  file inside your New Folder  ‘micriumos_usbdcdcacm\SimplicityStudio’ and rename it ‘SLSTK3701A_micriumos_usbdcdcacm.slsproj’ 

We will be adding our new workspace, so launch Simplicity Studio and connect the SLSTK3701A_EFM32GG11 board to the PC.

Add workspace by right-clicking anywhere inside the Project Explorer box and Select Import > MCU Project

 

Use the Browse button to locate the ‘SLSTK3701A_micriumos_usbdcdcacm.slsproj’ and click Next>

File location: 'C:\SiliconLabs\SimplicityStudio\v4\developer\sdks\gecko_sdk_suite\v2.4\app\mcu_example\SLSTK3701A_EFM32GG11\micriumos_usbdcdcacm\SimplicityStudio'

 

Since you already have your board connected, it should all be auto-detected. Leave everything by default making sure that there is an SDK selected, then click Next>

 

You can either change the name of the project or keep the default, then click Finish.

 

Configuration Files

 We will now need to modify the project configuration files in order to include Micrium OS USBD CDC-ACM class as part of our build.

Start by expanding the Includes section in the Project Explorer panel, then expand the configuration folder as shown in the image below. After that, double-click on the rtos_configuration.h to open it in the editor.

 

As soon as you try to edit the rtos_description.h, you will be presented a Warning indicating you are editing an SDK file. Click on Edit in SDK.

Add the following #define in rtos_description.h to indicate Micrium OS that you want to use CDC ACM class.

#define  RTOS_MODULE_USB_DEV_ACM_AVAIL
#define  RTOS_MODULE_USB_DEV_CDC_AVAIL

Remove the following #define in rtos_decription.h

#define  RTOS_MODULE_USB_DEV_HID_AVAIL

 

Tell Micrium OS you want to use the USBD CDC-ACM demo by modifying ex_description.h. Expand the Includes section in the Project Explorer panel, then expand the project folder as shown in the image below. After that, double-click on the ex_description.h to open it in the editor.

As soon as you try to edit the ex_description.h, you will be presented a Warning indicating you are editing an SDK file. Click on Edit in SDK.

Remove the following #define in ex_decription.h

#define  RTOS_MODULE_USB_DEV_HID_AVAIL

Add the following #define in ex_description.h to indicate Micrium OS that you want to use CDC-ACM class.

#define  RTOS_MODULE_USB_DEV_ACM_AVAIL

 

Adding USBD Class and Demo

Expand the src section in the Project Explorer panel and remove the ‘ex_usbd_hid_mouse.c’ linked file.

 

Select Import > MCU Project by right-clicking on src section as shown on image below

 

Choose ‘More Import Options…’  and select File System  on the next window that pops-up as shown on the images below

 

Use Browse button and add ‘ex_usbd_cdc_acm_terminal.c’ example as shown on image below, and click Finish.

File location: `C:\SiliconLabs\SimplicityStudio\v4\developer\sdks\gecko_sdk_suite\v2.4\app\micrium_os_example\usb\device\all`

 

Expand the usb>source>device>class section in the Project Explorer  panel and right-click on class. Select Import > MCU Project  and add the USBD CDC ACM class file as shown on images below

 

Use the Browse button to locate the CDC-ACM files to be added as shown below.

File location: `C:\SiliconLabs\SimplicityStudio\v4\developer\sdks\gecko_sdk_suite\v2.4\platform\micrium_os\usb\source\device\class`

 

Running the Example

You can now build your application and flash it on the board. Once the application starts running, you should see LED0 on the board blinking which means all the initialization was done correctly; therefore, we can now test the USBD CDC-ACM demo.

Open Windows Device Manager and expand the 'Ports (COM & LPT)' section. 

Use a Micro-USB B cable to connect the PC to the EFM32GG11 board. As soon as you connect it, Windows will enumerate the device and display it in 'Ports (COM & LPT)' as shown in the image below. Keep in mind that Windows is the one assigning the port number (COM7)  to my device.

 

Once you know the serial port number, we can use any serial terminal application and  open a terminal window.  The images below shows the terminal configurations and the CDC-ACM demo output.

 

If you work with Micrium OS, chances are you will eventually encounter some macro prefixed with RTOS_ASSERT which traps your task in an infinite loop.  Micrium OS has two types of ASSERTs, Critical ASSERTs and Debugging ASSERTs. The former type of ASSERT is intended to catch severe errors which may prevent the system from functioning normally such as a module failing to initialize correctly. On the other hand, Debugging ASSERTs are used to catch ordinary errors returned from an API call so that they are found quickly while debugging. However, the question naturally arises: should my system crash because I passed a bad delay value to OSTimeDly?

 

There are a few options to customize how these conditions are handled in your system.

1. You can disable debugging ASSERTs, which will also disable error checking. This is recommended once the project is stable and ready for production.

2. You can force the ASSERTs to return a value, with some caveats.

In order to make these changes, you must modify this section of rtos_cfg.h.

 

Option 1 requires changing the MASK to RTOS_CFG_MODULE_NONE.

Option 2 requires modifying the DBG macro so that it returns the error value.

However, you must be careful not to use any ASSERT_DBG() macros at the top level of your task; you may unintentionally return from the task if you do so.

 

For more details on ASSERTs, please refer to the following pages:

https://doc.micrium.com/display/OSUM50500/Micrium+OS+Asserts+Programming+Guide

https://doc.micrium.com/display/OSUM50500/RTOS+Compile-Time+Configuration

 

Background

The Micrium OS Examples in Simplicity Studio are very easy to access: You connect your Starter Kit and Simplicity Studio will display the list of examples as shown below:

 

For more information on how to access the Micrium OS Examples from Simplicity Studio you can see this document:

https://www.silabs.com/documents/public/training/wireless/micrium-os-examples.pdf

 

 

Revealing the 57 Hidden Gems

In this blog, I’m going to show you how to access the additional Micrium OS Examples that are not available from Simplicity Studio's Launcher Perspective.

There are 57 examples that demonstrate how to initialize the Micrium OS modules to perform the most basic operations:

Micrium OS Module		Example
CANopen		CANopen Module Initialization Example
		CANopen Node Start Example
		CANopen Object Dictionary Read/Write Example
File System		File System Module Initialization Example
		File Read/Write Example
		File Read/Write with Posix API Example
		File Multi-Descriptors Example
		Entry Path Example
		Block Device Read/Write Example
		Media Polling Example
Network	FTP Client	Send Data from a buffer to a file on an FTP Server
		Upload a file to an FTP Server
		Receive a file into a buffer
		Download a file from an FTP server
	HTTP Client	HTTP Client Initialization Example
		HTTP Client GET Request Examples
		HTTP Client POST Request Examples
		HTTP Client PUT Request Examples
		HTTP Client Persistent Connection Examples
		HTTP Client Multi-connection Examples
	HTTP Server	HTTP Server Initialization Example
		Simple Server That Uses No File System
		Basic Server That Uses the HTTP Static File System
		Basic Server That Uses Micrium OS File System
		Server That Handles REST Requests
		Server That Handles Webpages, REST Requests and Authentication Support
		Basic Secure Server That Uses SSL-TLS and the HTTP Static File System
	IPerf	IPerf Initialization Example
	MQTT Client	MQTT Client Initialization Example
		MQTT Client Connect Example
		MQTT Client Publish Example
		MQTT Client Subscribe Example
		MQTT Client Echo Example
	Network Core	Network Module(s) Initialization Example
		Network Core Initialization Example
		Start Network Interface(s) Example
	SMTP Client	SMTP Client Initialization Example
		SMTP Client Send Email Example
	SNTP Client	SNTP Client Initialization Example
		Basic SNTP Current Time Retrieve
	Telnet Server	Telnet Server Initialization Example
		Telnet Server Instance Example
	TFTP Client	Download and Upload a File to a TFTP Server
USB Device	Audio Class	USB Device Audio Class Loopback Example
	CDC ACM Class	USB Device CDC ACM Class Terminal Example
	CDC EEM Class	USB Device CDC EEM Class Example
	USB Device Core	USB Device Core Initialization Example
	HID Class	USB Device HID Class Mouse Example
	MSC Class	USB Device MSC Class Ramdisk LUN Example
		USB Device MSC Class Ramdisk Shared Example
	Vendor Class	USB Device Vendor Class Loopback Example
USB Host	Android Accessory Class	USB Host Android Accessory Class Example
	CDC ACM Class	USB Host CDC ACM Class Example
	USB Host Core	USB Host Module Simple Initialization Example
		Simple Device Port Operation Example
	MSC Class	USB Host MSC Class Example
	USB-to-Serial Class	USB Host USB-to-Serial Class Example
Table 1. The Hidden Micrium OS Examples

 

 

How to run the hidden Micrium OS Examples

The process of including, configuring and initializing the examples is the same for all the examples and can be summarized as follows:

Start off with one of the examples available through Simplicity Studio by connecting your Kit and selecting an Example from the list as illustrated in Figure 1.

If the example project does not have the Micrium OS module files, then you need to include them by inserting in your project the folder located at ${StudioSdkPath}/platform/micrium_os/[module]/include and ${StudioSdkPath}/platform/micrium_os/[module]/source/[module] and configuring your compiler's include paths with the new paths.

Locate the header file rtos_description.h and insert the macro necessary to enable the module. For the full list of macros see this document.

Make sure you have in your project all the configuration files located in STUDIO_SDK_LOC\platform\micrium_os\cfg

Explore the examples listed in Table 1, select the one that you want and follow the corresponding hyperlink.

       The hyperlink will take you to the example's documentation which provides four things:

• Description: Brief description of the example
• Configuration: The name of the #define that needs to be defined in ex_description.h
• Location: The location of the files that need to be included
• API: The API that needs to be called from your application to start the example

Locate the header file ex_description.h and define the corresponding macro if necessary as described in the example's documentation section: Configuration.

Include in your Simplicity Studio project the required files as listed in the example's documentation section: Location. In this step you can either create a link to the original folder or make a copy of the files and place them in your own workspace directory.

Configure your compiler's include paths with the new paths where the header files are located.

Insert a #include in your application, of the header file where the API to start the example is declared and call the API from your application to get the example started as described in the example's documentation section: API.

 

 

Example

To illustrate the process, I'm going to provide an example where one is interested in running an HTTP server:

Connect the SLSTK3701A and select the example SLSTK3701A_micriumos_net from Simplicity Studio.

Inspect which modules are included in the project by looking at the folder net in the Project Explorer. There you will notice that the module HTTP Server is missing.

Include the HTTP Server module by creating a new Linked Folder located at STUDIO_SDK_LOC\platform\micrium_os\net\source\http\server

Open the new folder Properties and either include or exclude the folder from compilation as necessary from the section C/C++ Build.

Open the Project Properties and insert the location to the new header files ${StudioSdkPath}/app/micrium_os_example/net/http/server in the section C/C++ General -> Paths and Symbols

Locate and open the header file rtos_description.h and insert the following line to enable the new HTTP Server Module: #define  RTOS_MODULE_NET_HTTP_SERVER_AVAIL

Copy the configuration files from STUDIO_SDK_LOC\platform\micrium_os\cfg to your own workspace directory and make sure the compiler is aware of this include path.

Look at Table 1, locate the Example Basic Server That Uses the HTTP Static File System and explore the documentation.

Open the header file ex_description.h and insert the following line to enable the example: #define  EX_HTTP_SERVER_INIT_AVAIL

Create a new Folder named Examples and then create a Linked Folder in it that points to STUDIO_SDK_LOC\app\micrium_os_example\net\http\server

Open the Project Properties and insert the path ${StudioSdkPath}/app/micrium_os_example/net in the section C/C++ General -> Paths and Symbols

Open the file ex_main.c and insert the following line at the top: #include  "http/server/ex_http_server.h"

From the same file ex_main.c, locate the calls to the functions Ex_NetworkInit() and Ex_Net_CoreStartIF() and insert right after them, a call the following API to get the example started: Ex_HTTP_Server_InstanceCreateStaticFS();

 

 

The following blog explains a simple way of detecting task stack overflows while debugging your Micrium OS application.

Micrium OS Kernel Red Zone

The kernel's red zone is a feature that, when enabled through OS_CFG_TASK_STK_REDZONE_EN in os_cfg.h creates a monitored zone at the end of a task's stack. The length of the red zone is user-configurable via the #define OS_CFG_TASK_STK_REDZONE_DEPTH in os_cfg.h. By default, this is set to 8 stack elements (CPU_STK). 

When the red zone is enabled, every time a task is switched out, either at the task level or at the interrupt level, the kernel checks if the red zone has been hit. By default, a software exception is thrown with the use of the CPU_SW_EXCEPTION macro in the ARMv7m port. However, if you want more control over what your application should do in the event that the red zone is hit, you can turn on the application hooks by setting OS_CFG_APP_HOOKS_EN to DEF_ENABLED in os_cfg.h.

Using the Red Zone Application Hook

If you decided that you want your application to determine what to do in the event that a task hits the red zone instead of throwing a software exception, then you will have to define a hook function to do so.

A simple example:

static  void  RedzoneHitHook (OS_TCB  *p_tcb)
{
	BSP_LedSet(0);
	while(1);
}

 

With that, you can tell that if you see LED0 permanently on and with your code trapped at the while loop you have hit the red zone. You can then check p_tcp->NamePtr in your local variables panel and find what was the task that hit the limit.

Don't forget to assign the red zone hit hook pointer to your custom function. Using the example above:

OS_AppRedzoneHitHookPtr = RedzoneHitHook;

 

Make sure that this is added prior to calling OSStart() otherwise the pointer is never assigned to your application hook.

For more details about detecting stack overflows and the red zone, visit the following link: https://www.micrium.com/detecting-stack-overflows-part-2-of-2/

Over and over, customers tell us they want a wireless link to just work so they can move on and focus on the application they're designing. This week, we delivered on this challenge with the introduction of Wireless Xpress, which gives designers the freedom to go from out of box to prototype within a few hours – versus months – with no software development necessary.

Wireless Xpress provides a configuration-based development experience with everything developers need, including certified Bluetooth® 5 Low Energy (LE) and Wi-Fi® modules, integrated protocol stacks and easy-to-use tools supported by the Silicon Labs Gecko OS operating system.

The new solution simplifies wireless development and eliminates the daunting task of working in numerous and complicated wireless development interfaces. Today’s IoT development teams are often burdened with importing numerous stacks of software, dealing with hundreds of APIs and complex RF integration obstacles, along with writing hundreds of hours of code. Because of these complexities, wireless development is hard to come by, and IoT companies often need to outsource the development, an extremely costly and time-intensive process that slows down time to market. Wireless Xpress removes the need for wireless development since we’ve already done the work for you.

Then there’s cloud connectivity – an onerous challenge for design teams to build from the ground up.  Wireless Xpress provides instant cloud connectivity and has built-in firmware updates, along with the ability to retrieve updates and push them out to devices in the field. This functionality removes the need for our customers to pay for subscription-based services to ensure these updates are managed.

Wireless Xpress addresses all of these challenges head-on without a big stack. We take on as much firmware responsibility as possible, with all configuration occurring in the Gecko API.  Wireless Gecko is not codeable, but configurable, freeing designers from the headache of wireless design by getting it all in one box.

 

Putting Application First, Versus Network

Another challenge solved by the new solution, and especially beneficial for low-power applications, is MCU processing constraints. An MCU in a typical wireless design is handling all of the network processing demands versus application needs, creating a situation where customers are often paying more than they need for an MCU. Wireless Xpress offloads the embedded host processing from the MCU and handles processing demands inside the package, reducing the processing performance required and optimizing the chip-set. With Wireless Xpress, you can use a bare bone 8-bit MCU for applications that would have otherwise needed a 32-bit because of RAM, flash, etc. demands.

 

Support Down to the Silicon

With the Wi-Fi and Bluetooth modules, Silicon Labs is able to go all the way down to the silicon to find a problem. When you look at other pre-programmed modules on the market, what you find is module vendors are not SoC designers – the silicon in these products is from other companies. Therefore, in the support structure, problems tend to be punted to the underlying silicon vendor. This structure really goes against the ease of use experience. Wireless Xpress gives customers one point of contact for wireless design, making it much easier for support and troubleshooting. It’s our silicon – we control every part of the flow, giving us the advantage to optimize design better than anyone on the market.

Our Bluetooth and Wi-Fi modules are pre-programmed, pre-qualified and are pin for pin compatible with our portfolio of products. And they all run through the Gecko Xpress API, which we have already tested to ensure its reliability and flexibility. We’re taking care of the wireless interface on behalf of the customer and giving them back the 3-6 months it would take to build all of the connectivity from scratch.

So many of our customers seeking wireless connectivity are long-standing, established companies in markets that don’t have the in-house resources nor budget to invest in wireless connectivity talent – these companies’ main agenda is to make exceptional products for their markets. Wireless Xpress gives these companies the opportunity to obtain the wireless expertise they need in one package – giving time back to the developers to worry about their own customer needs – instead of complex wireless scenarios that demand too much time and money.

Wireless Xpress is the latest culmination of our strong customer relationships – we listen and design accordingly. Stay tuned as Silicon Labs continues to deliver the IoT solutions designers want to get innovative and high-performing products to the market as fast as possible.

Learn more at silabs.com silabs.com/products/wireless/xpress. 

 

Overview

Micrium has a long history of providing very reliable kernels as seen with uC/OS-II and uC/OS-III, both still sold and used in many products today. Micrium OS Kernel is no exception to this and one common trait seen across all of these kernels is they are extremely configurable. A common question developers ask when evaluating real-time kernels is what is the kernel’s footprint for RAM and ROM. Micrium OS Kernel does not have a set number for RAM or ROM but instead a general range: 6-24KB ROM and 3-4KB of RAM. The reason for this is every part of the kernel, with the exception of the scheduler, can be enabled or disabled through a number of configuration header files.

Micrium OS Kernel by default uses an internal heap to allocate memory for its internal data structures and internal task stacks. The heap provides a simple, convenient way to allow a user to get a kernel project up and running quickly. The drawback to using the heap is there may be some RAM allocated to the heap that ends up not being used. This article will cover how to modify the Giant Gecko Series 1 Starter Kit (SLSTK3701A) Micrium OS Blink example to disable the internal heap and statically allocate memory for the internal data structures and task stacks. Nothing covered in this example is specific to the Giant Gecko Series 1, so these steps can be taken on any Micrium OS Kernel project.

Note: The file that is being modified, ex_main.c, is available for download at the bottom of this post.

Creating the Micrium OS Blink project

These steps assume Micrium OS Kernel is already installed in the most recent SDK version of a Simplicity Studio install. If it is not, go through the Update Software wizard for the Giant Gecko Series 1 to install all of the necessary packages.

 

Go to File -> New -> Project… to bring up the new project wizard. Select Silicon Labs MCU Project and click Next.

Set the board to the EFM32GG11 Giant Gecko Starter Kit board. This should trigger the Part and SDK to be set. If it does not, set the part as shown above and choose the most recent version of the SDKs.  Note: Micrium OS Kernel must already installed before this step. 

Select Example and click Next. 

Search for the Micrium OS Blink project and click Next. 

Select either Link Libraries or copy sources or Copy contents. It Is important that the ex_main.c file is copied into the project so modifications can be made. Click Finish and the project will be loaded into the Simplicity IDE.

Modifying the configuration files

Starting with the blank Micrium OS Blink project, expand the micriumos_blink/cfg folder as shown above under the Includes folder. This folder has all of the Micrium OS configuration files.

#define  LIB_MEM_CFG_HEAP_SIZE  0uL

The first step is to set the Micrium heap to zero. In common_cfg.h there is a #define for LIB_MEM_CFG_HEAP_SIZE. This value defines the size of the Micrium OS heap and should be changed to 0. After setting the heap value to 0, the project would still compile without error but would fail to run as the memory allocation would fail during OSInit().

If presented with a warning similar to the above, select Make a Copy. Any edits made to header files in the SDK would affect all future Micrium OS projects.

#define  RTOS_CFG_EXTERNALIZE_OPTIONAL_CFG_EN  DEF_ENABLED

After disabling the heap, Micrium OS needs to be set to disable the default configurations for all internal data structures and task stacks. Open up rtos_cfg.h and locate the #define for RTOS_CFG_EXTERNALIZE_OPTIONAL_CFG_EN. Change it to DEF_ENABLED to disable the default configurations. At this point, compilation of the project will fail due to a number of InitCfg structures not being set.

Configuration Structs

The rest of the code for this walk-through will be written in ex_main.c. There are three structures that must be defined: OS_InitCfg, Common_InitCfg, and PlatformMgr_InitCfg. These structures are used internally in Micrium OS and by setting RTOS_CFG_EXTERNALIZE_OPTIONAL_CFG_EN to DEF_ENABLED, the default configs for these structs has been removed and must be implemented by the developer.

OS Config Structs

struct  os_init_cfg {
    OS_STACK_CFG         ISR;
    OS_MSG_SIZE          MsgPoolSize;
    CPU_STK_SIZE         TaskStkLimit;
    OS_STACK_CFG         IdleTask;
    OS_TASK_CFG          StatTaskCfg;
    OS_TASK_CFG          TickTaskCfg;
    OS_TASK_CFG          TmrTaskCfg;
    MEM_SEG             *MemSeg;
};

The OS_INIT_CFG structure defines all of Micrium OS Kernel’s runtime configuration. It contains the stack config for all of the internal tasks (Idle, Tick, Timer, Stat), as well as the interrupt stack and an internal memory segment for internal kernel objects. The TaskStkLimit parameter will be set to zero as it is no longer used, but remains for backwards compatibility with previous versions. If an internal task has been disabled in os_cfg.h, that task’s configuration can be omitted from the OS_InitCfg.

struct  os_task_cfg {
    CPU_STK             *StkBasePtr;
    CPU_STK_SIZE         StkSize;
    OS_PRIO              Prio;
    OS_RATE_HZ           RateHz;
};

The OS_TASK_CFG structure is used to configure the Tick task, Statistics task and the Timer task. Each task will need a stack size and memory allocated for it, a priority set and the rate that the task will run at. Its important to remember that the stack size is not in bytes but stack units which are set to the width of the CPU (32 bits in this case); so a stack size of 128 stack units results in a 512 byte stack. Also, the timer task and stat task can not have a rate higher than the tick task due to being based off of the OS tick rate.

struct  os_stack_cfg {
    CPU_STK             *StkBasePtr;
    CPU_STK_SIZE         StkSize;
};

The OS_STACK_CFG structure is used for the Idle task and the ISR stack. Neither task has a priority (idle task defaults to the lowest priority, ISR is for interrupt context only) or rate associated with the task, so it only contains the stack size and location.

Common Config Struct

typedef  struct  common_init_cfg {
    MEM_SEG             *CommonMemSegPtr;

#if (RTOS_CFG_LOG_EN == DEF_ENABLED)
    COMMON_CFG_LOGGING   LoggingCfg;
    MEM_SEG             *LoggingMemSegPtr;
#endif
} COMMON_INIT_CFG;

The COMMON_INIT_CFG struct is used during the init of the common module. Typically the CommonMemSegPtr is set to DEF_NULL and logging is disabled. For this example, this will also be the case.

Platform Manager Struct

typedef  struct  platform_mgr_init_cfg {
    CPU_SIZE_T  PoolBlkQtyInit;
    CPU_SIZE_T  PoolBlkQtyMax;
} PLATFORM_MGR_INIT_CFG;

The PLATFORM_MGR_INIT_CFG struct is used for the initialization of the platform manager module. This module is used to describe hardware capabilities of peripherals such as network interfaces, USB interfaces or file systems.  Normally the platform manager pulls in memory from the heap but for a kernel-only project no memory is needed so the number of blocks can be set to zero. Unfortunately even though the platform manager is not used in a kernel-only project, a configuration is still required.

Configuring Micrium OS Blink

Using the information covered in the previous section, this part will cover how to configure ex_main.c in the Micrium OS Blink project to use these configuration structures.

Kernel Config Defines

This section covers only using #defines to set configurations. Since all internal tasks are configurable these defines will check to see if the tasks are enabled before adding them to the overall OS config.

//////////////////////////////
// Micrium OS Configuration //
//////////////////////////////
#define  TICK_TASK_RATE_HZ                  1000u
#define  STAT_TASK_RATE_HZ	                 100u
#define  TIMER_TASK_RATE_HZ                   10u
#define  MSG_POOL_ELEMENTS                     5u

/////////////////////
// Task Priorities //
/////////////////////
#define  TICK_TASK_PRIO                        0u
#define  TIMER_TASK_PRIO                       4u
#define  STAT_TASK_PRIO                        5u
#define  EX_MAIN_START_TASK_PRIO              21u

//////////////////////
// Task Stack Sizes //
//////////////////////
#define  TICK_TASK_STK_SIZE                  128u
#define  STAT_TASK_STK_SIZE                  128u
#define  TIMER_TASK_STK_SIZE                 128u
#define  IDLE_TASK_STK_SIZE                  128u
#define  ISR_STK_SIZE                        128u
#define  EX_MAIN_START_TASK_STK_SIZE         512u

The first step is to set some defines for the kernel configuration. This includes the task stack sizes and priorities, the internal task rates and the message pool elements.

• Task priorities can range from 0 to OS_CFG_PRIO_MAX (defined in os_cfg.h) with 0 being the highest priority.
• The task stack sizes are specified in stack units which correspond to the width of the CPU, not bytes, so it is important to remember that a stack size of 128 stack units is actually 512 bytes.
• The rates for the tick, timer and stat task are specified in hertz. Typical tick rate for the tick task is 1000Hz, typical timer task rate is 100Hz and typical stat task rate is 10Hz.

////////////////////////////////
// Message Pool Configuration //
////////////////////////////////

#define  MSG_POOL_SIZE      MSG_POOL_ELEMENTS * sizeof(OS_MSG)
#define  MSG_POOL_CFG       .MsgPoolSize     = MSG_POOL_ELEMENTS, \
							.MemSeg          = &MsgPoolMemSeg,

The next section to define is the message pool configuration. The message pool is used for the message queues and the number of message pool elements should always match the total number of queue entries in the entire system. For example if there is one OS Queue that has 10 entries and one OS Task Queue with 20 entries, MSG_POOL_ELEMENTS should be set to 30 to guarantee there is enough entries available for all of the message queues.

/////////////////////////////
// Tick Task Configuration //
/////////////////////////////
#if (OS_CFG_TASK_TICK_EN == DEF_ENABLED)
#define  TICK_TASK_CFG                  .TickTaskCfg =                        \
                                        {                                     \
                                            .StkBasePtr = &TickTaskStk[0],    \
                                            .StkSize    = TICK_TASK_STK_SIZE, \
                                            .Prio       = TICK_TASK_PRIO,     \
                                            .RateHz     = TICK_TASK_RATE_HZ   \
                                        },
#else
#define  TICK_TASK_CFG
#endif

/////////////////////////////
// Stat Task Configuration //
/////////////////////////////
#if (OS_CFG_STAT_TASK_EN == DEF_ENABLED)
#define  STAT_TASK_CFG                  .StatTaskCfg =                        \
                                        {                                     \
                                            .StkBasePtr = &StatTaskStk[0],    \
                                            .StkSize    = STAT_TASK_STK_SIZE, \
                                            .Prio       = STAT_TASK_PRIO,     \
                                            .RateHz     = STAT_TASK_RATE_HZ   \
                                        },
#else
#define  STAT_TASK_CFG
#endif

//////////////////////////////
// Timer Task Configuration //
//////////////////////////////
#if (OS_CFG_TMR_EN == DEF_ENABLED)
#define  TIMER_TASK_CFG                 .TmrTaskCfg =                         \
                                        {                                     \
                                            .StkBasePtr = &TimerTaskStk[0],   \
                                            .StkSize    = TIMER_TASK_STK_SIZE,\
                                            .Prio       = TIMER_TASK_PRIO,    \
                                            .RateHz     = TIMER_TASK_RATE_HZ  \
                                        },
#else
#define  TIMER_TASK_CFG
#endif

The Tick Task, Stat Task and Timer Task all use the OS_TASK_CFG structure so using the values defined from the Micrium OS Configuration section above, their declarations are fairly similar. The only variable not yet covered in these structs is the stack pointer. The stack pointer variables will be declared a littler farther down in ex_main.c, right now this is just #defines to be included later on.

/////////////////////////////
// Idle Task Configuration //
/////////////////////////////
#if (OS_CFG_TASK_IDLE_EN == DEF_ENABLED)
#define  IDLE_TASK_CFG				   .IdleTask =                            \
                                       {                                      \
                                           .StkBasePtr  = &IdleTaskStk[0],    \
                                           .StkSize     = IDLE_TASK_STK_SIZE  \
                                       },
#else
#define  IDLE_TASK_CFG
#endif

///////////////////////
// ISR Configuration //
///////////////////////
#define  ISR_CFG                       .ISR =                                 \
                                       {                                      \
                                           .StkBasePtr  = &ISRStack[0],       \
                                           .StkSize     = ISR_STK_SIZE        \
                                       },

The idle task and ISR configuration both use OS_STACK_CFG. Similar to the ones using OS_TASK_CFG, these configs use the stack size defines from the Micrium OS Configuration section above and the stack variables will be defined later on.

////////////////////////////////
// Micrium OS  Configurations //
////////////////////////////////
#define  OS_INIT_CFG_APP            {                                \
						                ISR_CFG                      \
							            IDLE_TASK_CFG                \
							            TICK_TASK_CFG                \
							            STAT_TASK_CFG                \
							            TIMER_TASK_CFG               \
                                        MSG_POOL_CFG                 \
                                        .TaskStkLimit = 0u,          \
                                    }

#define  COMMON_INIT_CFG_APP        {                                \
                                        .CommonMemSegPtr = DEF_NULL  \
                                    }

#define  PLATFORM_MGR_INIT_CFG_APP  {                                \
                                        .PoolBlkQtyInit = 0u,        \
                                        .PoolBlkQtyMax  = 0u         \
                                    }

Using the #defines for the message pool, internal tasks and the ISR stack, the OS_INIT_CFG_APP define can be set. As mentioned earlier the TaskStkLimit can be set to zero as it is no longer used.

The COMMON_INIT_CFG_APP define only has one variable, CommonMemSegPtr defined. The other variables in the struct are only enabled if the logging module is enabled. Since no modules in common need memory for this application the MemSegPtr will be set to DEF_NULL to signal it is not in use.

The PLATFORM_MSG_INIT_CFG_APP define is similar to COMMON_INIT_CFG_APP, the two fields in it can be set to zero as its not needed for this application.

Kernel Config Variables

Now that the defines have all been set, the stacks need to be created and the config defines need to be set to the necessary variables for Micrium OS Kernel to pull them in.

//////////////////////////
// Micrium OS Variables //
//////////////////////////

#if (OS_CFG_TASK_IDLE_EN == DEF_ENABLED)
static  CPU_STK  IdleTaskStk[IDLE_TASK_STK_SIZE];
#endif

#if (OS_CFG_TASK_TICK_EN == DEF_ENABLED)
static  CPU_STK  TickTaskStk[TICK_TASK_STK_SIZE];
#endif

#if (OS_CFG_STAT_TASK_EN == DEF_ENABLED)
static  CPU_STK  StatTaskStk[STAT_TASK_STK_SIZE];
#endif

#if (OS_CFG_TMR_EN == DEF_ENABLED)
static  CPU_STK  TimerTaskStk[TIMER_TASK_STK_SIZE];
#endif

static  CPU_STK  ISRStack[ISR_STK_SIZE];

#if (MSG_POOL_ELEMENTS > 0)
static  MEM_SEG    MsgPoolMemSeg;
static  CPU_INT08U MsgPoolMem[MSG_POOL_SIZE];
#endif

const   OS_INIT_CFG             OS_InitCfg          = OS_INIT_CFG_APP;
const   COMMON_INIT_CFG         Common_InitCfg      = COMMON_INIT_CFG_APP;
const   PLATFORM_MGR_INIT_CFG   PlatformMgr_InitCfg = PLATFORM_MGR_INIT_CFG_APP;

The stack variables will only be created if the tasks are enabled in os_cfg.h. If the task is enabled, the size is pulled in from the configuration above. The ISR stack is always created because its needed in every Micrium OS project. The message pool is only created if it is needed.

The OS_INIT_CFG, COMMON_INIT_CFG and PLATFORM_MGR_INIT_CFG structs MUST be named OS_InitCfg, Common_InitCfg and PlatformMgr_InitCfg. This is due to the RTOS_CFG_EXTERNALIZE_OPTIONAL_CFG_EN define set in the rtos_cfg.h. Micrium OS uses variables by these names to initialize the modules and if they are not defined in the user application, there will be compilation errors as the internal default config has been removed by the define in rtos_cfg.h.

Inits in main() and includes

After setting up all of the necessary variables for the config structs, two more changes must be made. 

#include  

The ex_main.c file needs to have the platform manager header file added to its list of includes. A compilation error will occur without this extra include.

int  main (void)
{
    RTOS_ERR  err;

#if (MSG_POOL_ELEMENTS > 0)
    Mem_SegCreate(          "Msg Pool Mem",                     /* Create the Message Pool memory segment               */
    		                &MsgPoolMemSeg,
				  (CPU_ADDR)&MsgPoolMem,
				             MSG_POOL_SIZE,
				             LIB_MEM_PADDING_ALIGN_NONE,
				            &err);
    APP_RTOS_ASSERT_DBG((RTOS_ERR_CODE_GET(err) == RTOS_ERR_NONE), 1);
#endif

    ...
}

The last change that needs to be made to ex_main.c is the addition of a Memory Segment Create. The OS config only allocates space for a memory segment. When the application starts up, its necessary to make a call to Mem_SegCreate to create the memory segment BEFORE the OSInit call is made. OSInit uses the memory segment and if it has not been initialized the application will fail to run.  

Building the new Blink project and comparing results

After all of these changes have been made to the Micrium OS Blink project, the project can be built by right clicking on the project name and selecting Build Project as shown above. 

Default Micrium OS Blink project RAM/ROM usage

Micrium OS Blink project RAM/ROM usage after adding external configuration

After building the project the console window will show the final sizes for RAM and ROM. As seen in the images above, the RAM usage is reduced from 24KB to just under 19KB simply by moving the internal tasks from the heap to the external config instead. 

The default RAM usage in this project is rather high to begin with because it includes SEGGER's SystemView code and the application task stack size is very large for such a simple project (currently set to 512 stack units/2048 bytes). To further reduce RAM usage in this project its possible to:

• Disable internal tasks that are not needed via os_cfg.h.
• Disable SEGGER SystemView code via os_cfg.h and os_cfg_trace.h
• Shrink the Main Start Task Stack Size 
• Reuse CSTACK after the OS has started up

The ex_main.c file is attached to this post and feel free to ask any questions in the forum below.

Almost all of Silicon Labs Starter/Development Kits include an onboard J-Link debugger, which is great to not only debug and flash your embedded application, but also to run SystemView.

SystemView as you probably know is the tool to record and analyze your Micrium OS Kernel events in real time.

However, the onboard J-Link can be slow depending on the rate of kernel events that your embedded application is creating. Overflow events occur when the SystemView buffer on your embedded target is full.

In this blog I'm gonna discuss the basic steps to prevent overflows and then I will describe the ultimate way to prevent overflows.

 

Steps to Prevent Overflows

1. Increase the buffer size to store the events:

Open the configuration file SEGGER_SYSVIEW_Conf.h and set the buffer size to 4096 as shown below:

#define SEGGER_SYSVIEW_RTT_BUFFER_SIZE           4096

 

2. In case you are running Simplicity Studio, close Simplicity Studio and let SystemView run by itself.

 

3. In case you are running Probe, close Probe and let SystemView run by itself.

 

4. Open the configuration file os_cfg_trace.h and decrease the number of events by disabling the following features:

#define  OS_CFG_TRACE_API_ENTER_EN               DEF_DISABLED

#define  OS_CFG_TRACE_API_EXIT_EN                DEF_DISABLED

 

5. If you are still having overflows after making the changes above, then the ultimate way to prevent overflows is to buy a much faster External J-Link from SEGGER: https://www.segger.com/products/debug-probes/j-link/

Most of our Starter Kits have a Debug Connector that you can use to connect the external J-Link. 

The following section describes how to connect your external J-Link to a Silicon Labs Starter Kit.

 

Connecting your External J-Link

1. First you need to configure your Starter Kit to reroute the debugging circuitry to the external debug connector. 

Open Simplicity Studio, select your Starter Kit, locate the section Debug Mode: MCU and then press the link Change as shown in the image below:

 

2. You may be asked to download an adapter firmware image. If so, press the button Yes.

 

3. The default Debug Mode is called MCU which means that your debugger is the Onboard J-Link.

 

4. Select from the drop-down the option IN which means that your debugger is an External J-Link as shown in the image below:

 

5. Connect your external J-Link to the debug connector on your Silicon Labs Starter Kit.

Depending on your kit, it may be one of the ones shown below.

The J-Link 19-pin 0.05" Cortex-M Debug Connector shown in Figure 3 may require a J-Link 19-pin Cortex-M Adapter available from SEGGER.

 

On the other hand, the standard 20-pin 0.1" JTAG Debug Connector shown in Figure 4 does not require any adapters and can be connected directly to your external J-Link.

 

For more information on how to configure your Starter Kit in the appropriate debugging mode, please consult your Starter Kit's User's Guide, the section On-Board Debugger, Debug Modes.

 

Related Links:

SystemView Installer: https://www.segger.com/downloads/free-utilities/#SystemView

SystemView User's Manual: https://www.segger.com/downloads/free-utilities/#Manuals

J-Link Debug Probes: https://www.segger.com/products/debug-probes/j-link/

J-Link 19-pin Cortex-M Adapter: https://www.segger.com/products/debug-probes/j-link/accessories/adapters/19-pin-cortex-m-adapter/

 

Whether you are currently running your embedded application on Silicon Labs hardware or other semiconductor, the migration path is the same as illustrated in Figure 1.

You should start from a working Micrium OS example and then move your embedded application over to the example project.

 

Once you move your embedded application to the Micrium OS baseline example project, you need to change the code that calls the FreeRTOS API.

The purpose of the attached PDF document is to describe the differences between the two kernels, offer plenty of side-by-side examples and mapping tables to help you in the process of migrating your embedded application.

 

For the upcoming Embedded World tradeshow in Nuremberg, Germany, the Silicon Labs MCU team is showing off some unique ways to ease the challenges of developing cloud-connected applications. The demo consists of the EFM32 Giant Gecko 11 MCU, which is running Micrium OS and connects to Amazon Web Services via the new XBee3 cellular module from Digi International.

 

This particular demo is quite simple – a closed-loop system with an MCU monitoring a temp sensor and controlling a fan. However, the real-world use cases that these building blocks and tools can scale to serve are much more profound.

For example, many smart city applications including bridge sensors, parking meters, waste management sensors, and others often consist of portable sensor devices that require seamless long-range connectivity to the cloud. They may be battery powered with user demands of 10+ year battery life. They may have lots of sensor inputs and extra features like button inputs and local displays. Finally, they might need to be designed quickly, but with a long field-upgradeable lifetime in mind. These are the types of applications that this demo speaks to, with Micrium OS, Giant Gecko 11, and Digi’s XBee3.

Micrium OS is running on the MCU and helps modularize the application functions. It’s helping the MCU maintain communication with the cellular module, monitor the temp sensor, drive the TFT display, and update control settings when local push buttons are pressed. By using Micrium, these various pieces can easily be divided and coded in parallel without having to worry about any messy integration at the end. In fact, this is exactly what the Embedded World demo team did – three different development teams in three different cities built the demo, and Micrium was the underlying glue that made it seamlessly come together.

Another challenge being addressed here is the connectivity piece. As devices are now adding wireless connectivity, there are lots of hurdles to clear: RF design in some cases, FCC certifications, understanding wireless networking, security, and more. Not only does Silicon Labs offer homegrown, low power SoCs and modules, but now Digi helps add simple cellular connectivity. The Digi XBee3 is a plug-and-play NB-IoT module that has built-in security and is pin-compatible with 3G and LTE-M modules. It’s programmable via MicroPython and comes pre-certified so developers can focus more on the application itself.

This brings us to the developer’s main focus, the application. The Giant Gecko 11 is a new 32-bit energy friendly microcontroller from Silicon Labs, and our the most capable yet. It helps simplify complex, cloud-connected applications with its large on-chip memory (2MB/512kB), lots of flexible sensor interfaces, SW and pin compatibility with other EFM32 MCUs, and unique low power capability to help prolong battery life. For example, not only does Giant Gecko 11 allow for autonomous analog and sensing in “Stop Mode” (1.6 uA), but it also has Octal SPI interface for external data logging, which could be used to reduce cellular transmission duty cycling.

There is one more unique offering in this demo. Considering that cellular connectivity might not be the solution for all IoT applications, the SW compatibility of Giant Gecko 11 and all EFM32s with Silicon Labs Wireless Geckos makes it easy to migrate to another wireless SoC or module, if needed. For example, some use cases and markets may use NB-IoT (such as this demo), while others might need their own proprietary sub-GHz solution (Flex Gecko).

For more information about what we’re doing at Embedded World, click here: https://www.silabs.com/products/wireless/internet-of-things.