Platform:

Using Gecko OS 2.1/2.0 or ZentriOS 1.5, or any earlier versions on AMW007/AMW037

Introduction:

As reported by many customers, rrror 0x7200 is returned when trying to establish TLS connection with 'some' servers. The error is caused by TLS handshaking failure. It is a known issue, and we have a fix for it. Please read below.

Root cause:

A TLS connection to a server that sends fragment sizes larger than 4K fails. The connection may fail during TLS handshaking, but it may fail at any time after connection if the server sends a fragment larger than 4K.

That is a known issue in Gecko OS 2.1 and earlier (also in ZentriOS 1.5 and earlier). Please see the known issues in the release notes here:

https://docs.silabs.com/gecko-os/2/amw007-w00001/latest/release-notes#known-issues

Solution:

We just released BETA Gecko OS 2.2.9 that has fixes for the 4K issue discussed above. To get access to this release, please issue the command 'ota -b 2.2.9'.
Kindly note that this is a BETA firmware (when this article is published), and once we collect all the feedback from waiting customers, will flip this to release. Beta releases should only be used for test and verification, not for mass production.

Also discussed here:

https://www.silabs.com/community/wireless/wi-fi/forum.topic.html/amw007_error_withtl-CIId

https://www.silabs.com/community/wireless/wi-fi/forum.topic.html/amw-037_https_reques-XgAj

Depending on WGM160P part number chosen by customer, WGM160P features or not an integrated chip antenna.

The WGM160P is certified for FCC/ISED and CE with the integrated antenna (see section 4.7 of the datasheet) or with an external antenna (See section 11.1 of the datasheet https://www.silabs.com/documents/login/data-sheets/wgm160p-datasheet.pdf). The WGM160P certification ID is provided in the datasheet so that certificates can directly be downloaded from the web (See section 11 of the datasheet).

The external antenna used for certification on RF port is 50 ohms connectorized coaxial dipole antenna with maximum gain of 2.14dBi, achieving at least -10dB return loss over WiFi frequency band.  An example of such external antenna, is the Pulse Part Number W1030.

Any external antenna of the same kind and with equal or less gain and at least same -10dB VSWR over the WiFi frequency band should be fine and should not void FCC/ISED certifications as long as spot-check testing is performed to verify that no performance changes compromising compliance have been introduced.
Any other antenna (such as a chip antenna, a PCB trace antenna or a patch) will require the customer to do some testing and apply for a C2PC (Class 2 Permissive Change) as indicated by the customer’s TCB (Telecommunication Certification Body).

With CE, anyway, customer has to perform certification test with the end-product.

You could find some explanations in the section 10.3 Power On, Reset, and Boot in the WF200 datasheet :  
https://www.silabs.com/documents/login/data-sheets/wf200-datasheet.pdf

Moreover there is also some details in https://www.silabs.com/documents/login/user-guides/ug382-wf200-hardware-design-ug.pdf in section 4,.

When device is not supplied yet, pin RESETn shall be set to LOW and No HIGH voltage is expected to be applied to input pin LP_CLK.
Once power supplies have settled, a delay of 100µs is recommended before releasing pin RESETn to HIGH.
When powering down the device, it is recommended to set RESETn pin back to LOW before shutting down its power supplies. 

The power down step sets the WF(M)200 in standby mode according to these two ways below:

• Our lower MAC API command SHUT_DOWN allows to put the chip in standby mode.
• Alternative way is to assert RESETn pin low, at the expense of slightly higher current consumption due to the internal 43kohms typ. pull-up resistor.