Si1153 RevB parts (Si1153-AB00-GM, Si1153-AB09-GM, Si1153-AB9X-GM) are launched in September 2018.
Comparing to Si1153 RevA parts, the major change is in interrupt modes. Si1153 RevA parts only support interrupt on every sample and whenever the sample is larger than a set threshold, while Si1153 RevB parts support multiple interrupt modes listed below. The host can configure ADCPOSTx registers to set different interrupt modes.
Mode 1: Interrupt on every sample.
Mode 2. Interrupt whenever the sample is larger/smaller than a set threshold.
Mode 3. Interrupt whenever the sample enters/exits the set threshold window.
Si1153 RevB is pin compatible with Rev A and fully backwards compatible in terms of software programming. Existing customers can easily switch to RevB parts without any changes. New customers can make use of the new interrupt mode in certain applications to reduce power consumption.
The Si1133/5x Optical Sensor EXP board now has an example project running on EFM32PG12 MCU to demonstrate our latest Si1153 for proximity/ambient light sensing and Si1133 for UV sensing. The example project will require an EFM32™ Pearl Gecko PG12 Starter Kit(SLSTK3402A) to plug in the Si1133/5x Optical Sensor EXP board through the 20pin expansion header.
The source code of the example project is provided in the attachment.
We also have a nice video describing all the features included in the demo. Please make sure to check it out before getting started.
Does Silicon Labs offer the SpO2 solution? If so, which sensor can be used to measure SpO2? Any example code available?
Answer
Red and IR LEDs are required for SpO2 measurement. Silicon Labs offers the SpO2 solution with Si1171K1-GM module, which has integrated 1 Green, 1 Red, and 1 IR LED. (https://www.silabs.com/products/sensors/biometric/si117x/device.si1171k1-gm)
SpO2 measurement can work on the finger-tip, but not on the wrist as the signal quality on the wrist is not good enough
for SpO2 calculation.
Silicon Labs provides the source code for finger-tip based HRM&SpO2 algorithm. The example project, as well as the user's guide, can be downloaded from the link below.
https://www.silabs.com/documents/public/software/EFR32MG_STK_Si117x_Static_HRM_example.zip
https://www.silabs.com/documents/public/user-guides/Si117x_Static_HRM_UsersGuide_Rev1_0.pdf
How to configure the MEASRATE and MEASCOUNT registers of Si1153 to perform autonomous measurements? Are there any restrictions?
Answer
Si153 can be configured to perform autonomous measurements. The time between each measurement is set to 800us * MEASRATE * MEASCOUNT. In general, it is recommended to leave MEASCOUNT to 1. For example, if users want to perform 10Hz measurements, they can set MEASRATE to 125 and MEASCOUNT to 1. (800us * 125 * 1 = 100ms)
However, due to an internal issue, MEASRATE must be set to a value smaller than 625. In another word, if users want to perform measurements at a rate slower than 2Hz(0.5s), they should increase MEASCOUNT settings instead of MEASRATE.
In addition, it is not recommended to change MEASRATE or MEASCOUNT settings during the measurement. Users should stop the measurement first, update the value of those registers and then start the measurement again.
While we will still provide the Android and iOS source code for the sensor puck apps, the sensor puck is actually no longer actively supported. We recommend using the thunderboard sense instead. If you still wish to obtain the app source please submit a support ticket.
How many different I2C addresses does Si1153 support? How to set them?
Answer
Si1153 supports 2 different I2C addresses. If the LED2 pin is high during the power-up, the sensor will come up with the default I2C address 0x53. If the LED2 pin is pulled low during the power-up, the sensor will use the alternate I2C address 0x52.
2. I2C communication failure
Question
What could be the cause of the host's failed communicate with the sensor through I2C interface?
Answer
1. LED3 pin MUST be pulled high during the power-up. If it's not, the sensor won't be powered up properly.
2. Check the I2C address and make sure that the correct I2C address is used.
3. Check the I2C timing specifications and see if that meets the requirement listed in Table 8.5 in the datasheet, especially the I2C frequency and rise/fall time.
3. Power-on reset
Question
Why does the host fail to communicate with the sensor upon power-on reset?
Answer
During the power-on reset, Vdd must drop below 0.5V for the sensor to properly reset itself. If the Vdd is held between 0.5V to 1V, the sensor will enter an unknown state and fail to power up normally.
4. 24bit mode
Question
Is it a true 24bit ADC output? What's the usage case of 24bit mode? Does the threshold interrupt mode work in 24bit mode?
Answer
No, the ADC only outputs samples in 16bit mode. However, the internal controller can accumulate multiple samples from the ADC to reduce the noise. The host can get 24bit output if it doesn't post-shift the result.
No, the host must set the sensor to 16bit output mode if it wants to receive interrupts on set thresholds.
5. Prox detection range
Question
What's the proximity detection range of Si1153?
Answer
Without lensing, the maximum proximity detection distance is about 50cm. A reliable working range is 30cm ~ 40cm.
With additional lensing, the proximity detection distance can reach up to 2m.
6. Sunlight immunity
Question
Which part supports the sunlight immunity feature? How to avoid saturation under direct sunlight?
Answer
Si1153-AA09-GM and Si1153-AA9X-GM parts have the on-die 940nm filter which is sunlight immune. To avoid saturation, set HSIG bit in the ADCSENSx register to 1 in outdoor applications.
7. Sensitivity
Question
How to adjust the sensitivity of Si1153?
Answer
HW_GAIN and LED Current settings can be increased to improve the sensitivity at long distances.
How many different I2C addresses does Si1133 support? How to set them?
Answer
Si1133 supports 2 different I2C addresses. If the AD pin is high during the power-up, the sensor will come up with the default I2C address 0x55. If the AD pin is pulled low during the power-up, the sensor will use the alternate I2C address 0x52.
2. I2C communication failure
Question
Why does the host fail to communicate with the sensor through the I2C interface?
Answer
There're a couple of possible causes:
a. Pin 7 MUST be pulled high during the power-up. If it's not, the sensor won't be powered up properly.
b. Check the I2C address and make sure that the correct I2C address is used.
c. Check the I2C timing specifications and see if that meets the requirement listed in Table 8.3 in the datasheet, especially the I2C frequency and rise/fall time.
3. Power-on reset
Question
Why could the host fail to communicate with the sensor upon power-on reset?
Answer
During the power-on reset, Vdd must drop below 0.5V for the sensor to properly reset itself. If the Vdd is held between 0.5V to 1V, the sensor will enter an unknown state and fail to power up normally.
4. UV index accuracy
Question
What's the UV index accuracy of Si1133?
Answer
With diffuser, the UV index accuracy can reach +/-0.75UVI. Without diffuser, the accuracy is about +/-2UVI.
5. UV spectrum response
Question
What's the UV spectrum response of Si1133 look like?
Answer
Si1133 is responsive to both UVA and UVB wavelength. Silicon Labs does not provide spectrum response information of Si1133.
6. Optical Design
Question
Why do Si1133 require a diffuser?
Answer
All standard UV instruments have diffusers and require the sensor to be facing straight up vertically regardless of where the sun is. Without a diffuser, the UV sensor will have limited view angle. This is the same for competitors’ product.
7. Sensor output
Question
Does the Si1133 output UV Index directly?
Answer
No, the ADC readings need to go through a set of coefficients, and the results will be the UV index. There are two sets of coefficients - one for diffuser designs and one for designs with no diffuser.
There're a total of 4 current consumption values used in the equation:
1. Standby Current: 1.25uA (Vdd = 3.3V)
2. Active Current (internal controller processing): 4.5mA (Vdd = 3.3V)
3. ADC Current (suspend mode): 0.525mA (Vdd = 3.3V)
4. LED Current: set by the host
Since the standby current is relatively small comparing to the rest, we can ignore that to simplify the estimation.
I = I_internal_controller + (I_adc_setup + I_adc_active) + I_led
The integration time of the ADC is controlled by the HW_GAIN setting. The default integration time is 24.4us and 24.4*2^HW_GAIN if HW_GAIN is set to non-zero values.
The internal controller processing time per measurement is 155us. The ADC setup time is 48.8us. The si1153 sensor will perform 2 back-to-back measurements, one with the LED on and the other with the LED off. Therefore, if we assume integration time is set to default and LED current is set to maximum 354mA, the total power consumption will be:
Can Si1153/33 sensors be used for ambient light sensing? How to convert ALS results to LUX values? Any example code available?
Answer
Only Si1153-AA00-GM and Si1133-AA00-GM parts can measure ambient light. Si1153-AA09-GM and Si1153-AA9X-GM parts cannot measure ambient light due to the on-die 940nm filter.
There's no simple equation to convert ALS measurement results to LUX values by any means. The only solution is to perform tests under certain light sources and calibrate ALS results against LUX values read from a LUX meter. Then find the ratio or formula to estimate LUX values based on ALS measurement data. Since it's an estimation, the accuracy won't be anywhere close to a LUX meter. Si1153/33 sensors CANNOT be used in LUX meter type of applications, but can still be used in applications that only require an approximate LUX level.
We've built a model to use 3 different channels' ALS measurement results to estimate LUX values. The example code is attached. However, the model is overly complicated and we recommend the customer to only use that as a reference and develop their own equation to estimate LUX.
Silicon Labs doesn't support ALS calibration for any applications.
Sensors Knowledge Base
Si1153 RevB Changes
Si1153 RevB parts (Si1153-AB00-GM, Si1153-AB09-GM, Si1153-AB9X-GM) are launched in September 2018.
Comparing to Si1153 RevA parts, the major change is in interrupt modes. Si1153 RevA parts only support interrupt on every sample and whenever the sample is larger than a set threshold, while Si1153 RevB parts support multiple interrupt modes listed below. The host can configure ADCPOSTx registers to set different interrupt modes.
Mode 1: Interrupt on every sample.
Mode 2. Interrupt whenever the sample is larger/smaller than a set threshold.
Mode 3. Interrupt whenever the sample enters/exits the set threshold window.
Si1153 RevB is pin compatible with Rev A and fully backwards compatible in terms of software programming. Existing customers can easily switch to RevB parts without any changes. New customers can make use of the new interrupt mode in certain applications to reduce power consumption.
Si1133/Si115x Optical Sensor Example Project on 32bit MCU
The Si1133/5x Optical Sensor EXP board now has an example project running on EFM32PG12 MCU to demonstrate our latest Si1153 for proximity/ambient light sensing and Si1133 for UV sensing. The example project will require an EFM32™ Pearl Gecko PG12 Starter Kit(SLSTK3402A) to plug in the Si1133/5x Optical Sensor EXP board through the 20pin expansion header.
The source code of the example project is provided in the attachment.
We also have a nice video describing all the features included in the demo. Please make sure to check it out before getting started.
RHT Sensor FAQ
This is a list of links to for some of the most common questions regarding the use of humidity sensors.
1. Using multiple RHT sensors with the same I2C address
2. RH readings are too high
3. RH readings are too low
4. How to recover accuracy through a bake/hydration cycle
5. Using conformal coating with RHT sensor
6. Performing hot air rework with RHT sensor
7. Is the protective cover replaceable?
8. Example driver files for RHT sensor
SpO2 Solution Using Si117x Biometric Sensor
Question
Does Silicon Labs offer the SpO2 solution? If so, which sensor can be used to measure SpO2? Any example code available?
Answer
Red and IR LEDs are required for SpO2 measurement. Silicon Labs offers the SpO2 solution with Si1171K1-GM module, which has integrated 1 Green, 1 Red, and 1 IR LED. (https://www.silabs.com/products/sensors/biometric/si117x/device.si1171k1-gm)
SpO2 measurement can work on the finger-tip, but not on the wrist as the signal quality on the wrist is not good enough
for SpO2 calculation.
Silicon Labs provides the source code for finger-tip based HRM&SpO2 algorithm. The example project, as well as the user's guide, can be downloaded from the link below.
https://www.silabs.com/documents/public/software/EFR32MG_STK_Si117x_Static_HRM_example.zip
https://www.silabs.com/documents/public/user-guides/Si117x_Static_HRM_UsersGuide_Rev1_0.pdf
Si1153 MEASRATE and MEASCOUNT Register Settings
Question
How to configure the MEASRATE and MEASCOUNT registers of Si1153 to perform autonomous measurements? Are there any restrictions?
Answer
Si153 can be configured to perform autonomous measurements. The time between each measurement is set to 800us * MEASRATE * MEASCOUNT. In general, it is recommended to leave MEASCOUNT to 1. For example, if users want to perform 10Hz measurements, they can set MEASRATE to 125 and MEASCOUNT to 1. (800us * 125 * 1 = 100ms)
However, due to an internal issue, MEASRATE must be set to a value smaller than 625. In another word, if users want to perform measurements at a rate slower than 2Hz(0.5s), they should increase MEASCOUNT settings instead of MEASRATE.
In addition, it is not recommended to change MEASRATE or MEASCOUNT settings during the measurement. Users should stop the measurement first, update the value of those registers and then start the measurement again.
Can I get the Android and iOS source code for the sensor puck?
Si1153 FAQ
1. I2C address
Question
How many different I2C addresses does Si1153 support? How to set them?
Answer
Si1153 supports 2 different I2C addresses. If the LED2 pin is high during the power-up, the sensor will come up with the default I2C address 0x53. If the LED2 pin is pulled low during the power-up, the sensor will use the alternate I2C address 0x52.
2. I2C communication failure
Question
What could be the cause of the host's failed communicate with the sensor through I2C interface?
Answer
1. LED3 pin MUST be pulled high during the power-up. If it's not, the sensor won't be powered up properly.
2. Check the I2C address and make sure that the correct I2C address is used.
3. Check the I2C timing specifications and see if that meets the requirement listed in Table 8.5 in the datasheet, especially the I2C frequency and rise/fall time.
3. Power-on reset
Question
Why does the host fail to communicate with the sensor upon power-on reset?
Answer
During the power-on reset, Vdd must drop below 0.5V for the sensor to properly reset itself. If the Vdd is held between 0.5V to 1V, the sensor will enter an unknown state and fail to power up normally.
4. 24bit mode
Question
Is it a true 24bit ADC output? What's the usage case of 24bit mode? Does the threshold interrupt mode work in 24bit mode?
Answer
No, the ADC only outputs samples in 16bit mode. However, the internal controller can accumulate multiple samples from the ADC to reduce the noise. The host can get 24bit output if it doesn't post-shift the result.
No, the host must set the sensor to 16bit output mode if it wants to receive interrupts on set thresholds.
5. Prox detection range
Question
What's the proximity detection range of Si1153?
Answer
Without lensing, the maximum proximity detection distance is about 50cm. A reliable working range is 30cm ~ 40cm.
With additional lensing, the proximity detection distance can reach up to 2m.
6. Sunlight immunity
Question
Which part supports the sunlight immunity feature? How to avoid saturation under direct sunlight?
Answer
Si1153-AA09-GM and Si1153-AA9X-GM parts have the on-die 940nm filter which is sunlight immune. To avoid saturation, set HSIG bit in the ADCSENSx register to 1 in outdoor applications.
7. Sensitivity
Question
How to adjust the sensitivity of Si1153?
Answer
HW_GAIN and LED Current settings can be increased to improve the sensitivity at long distances.
Si1133 FAQ
1. I2C address
Question
How many different I2C addresses does Si1133 support? How to set them?
Answer
Si1133 supports 2 different I2C addresses. If the AD pin is high during the power-up, the sensor will come up with the default I2C address 0x55. If the AD pin is pulled low during the power-up, the sensor will use the alternate I2C address 0x52.
2. I2C communication failure
Question
Why does the host fail to communicate with the sensor through the I2C interface?
Answer
There're a couple of possible causes:
a. Pin 7 MUST be pulled high during the power-up. If it's not, the sensor won't be powered up properly.
b. Check the I2C address and make sure that the correct I2C address is used.
c. Check the I2C timing specifications and see if that meets the requirement listed in Table 8.3 in the datasheet, especially the I2C frequency and rise/fall time.
3. Power-on reset
Question
Why could the host fail to communicate with the sensor upon power-on reset?
Answer
During the power-on reset, Vdd must drop below 0.5V for the sensor to properly reset itself. If the Vdd is held between 0.5V to 1V, the sensor will enter an unknown state and fail to power up normally.
4. UV index accuracy
Question
What's the UV index accuracy of Si1133?
Answer
With diffuser, the UV index accuracy can reach +/-0.75UVI. Without diffuser, the accuracy is about +/-2UVI.
5. UV spectrum response
Question
What's the UV spectrum response of Si1133 look like?
Answer
Si1133 is responsive to both UVA and UVB wavelength. Silicon Labs does not provide spectrum response information of Si1133.
6. Optical Design
Question
Why do Si1133 require a diffuser?
Answer
All standard UV instruments have diffusers and require the sensor to be facing straight up vertically regardless of where the sun is. Without a diffuser, the UV sensor will have limited view angle. This is the same for competitors’ product.
7. Sensor output
Question
Does the Si1133 output UV Index directly?
Answer
No, the ADC readings need to go through a set of coefficients, and the results will be the UV index. There are two sets of coefficients - one for diffuser designs and one for designs with no diffuser.
Si1153 Power Consumption
Question
How to calculate the total power consumption of Si1153? What are the major factors that impact power consumption?
Answer
A detailed power consumption breakdown of Si1153 is covered in Section 6 of the application note AN950:
https://www.silabs.com/documents/public/application-notes/AN950-Si1153-UG.pdf
There're a total of 4 current consumption values used in the equation:
1. Standby Current: 1.25uA (Vdd = 3.3V)
2. Active Current (internal controller processing): 4.5mA (Vdd = 3.3V)
3. ADC Current (suspend mode): 0.525mA (Vdd = 3.3V)
4. LED Current: set by the host
Since the standby current is relatively small comparing to the rest, we can ignore that to simplify the estimation.
I = I_internal_controller + (I_adc_setup + I_adc_active) + I_led
The integration time of the ADC is controlled by the HW_GAIN setting. The default integration time is 24.4us and 24.4*2^HW_GAIN if HW_GAIN is set to non-zero values.
The internal controller processing time per measurement is 155us. The ADC setup time is 48.8us. The si1153 sensor will perform 2 back-to-back measurements, one with the LED on and the other with the LED off. Therefore, if we assume integration time is set to default and LED current is set to maximum 354mA, the total power consumption will be:
I = (155us * 4.5mA + 48.8us * 525uA + 2* 24.4us * 525uA + 24.4us * 354mA) * Fs
where Fs is the sampling frequency of the measurement.
Si1153/33 Ambient Light Sensing and LUX calculation
Question
Can Si1153/33 sensors be used for ambient light sensing? How to convert ALS results to LUX values? Any example code available?
Answer
Only Si1153-AA00-GM and Si1133-AA00-GM parts can measure ambient light. Si1153-AA09-GM and Si1153-AA9X-GM parts cannot measure ambient light due to the on-die 940nm filter.
There's no simple equation to convert ALS measurement results to LUX values by any means. The only solution is to perform tests under certain light sources and calibrate ALS results against LUX values read from a LUX meter. Then find the ratio or formula to estimate LUX values based on ALS measurement data. Since it's an estimation, the accuracy won't be anywhere close to a LUX meter. Si1153/33 sensors CANNOT be used in LUX meter type of applications, but can still be used in applications that only require an approximate LUX level.
We've built a model to use 3 different channels' ALS measurement results to estimate LUX values. The example code is attached. However, the model is overly complicated and we recommend the customer to only use that as a reference and develop their own equation to estimate LUX.
Silicon Labs doesn't support ALS calibration for any applications.