Sending SAADC over BLE?

RE: Sending SAADC over BLE?

akshaey — Wed, 10 May 2017 09:15:13 GMT

Hi can anyone of you tell me, i used your program for saadc to uart over ble on sdk 11, the uart terminal on my computer is showing correct values from the board (COM), but the uart terminal on nrf toolbox app on my phone shows random garbage values, how to correct that so that i can send the values captured my sensor via ble to mobile app?

thanks

RE: Sending SAADC over BLE?

Stefan Birnir Sverrisson — Tue, 19 Apr 2016 12:26:29 GMT

Hi Filip

I don't see the example stopping after 135 events on my side using PCA10040 v1.1.0 with rev 1 nRF52832 on board. Are you using the same?

I tried to run the ble_app_uart_c example on my pca10028 board and got it to work right away with the ble_app_uart__saadc_timer_driven example. I connect to a uart terminal program (Realterm in my case) and the output appeared to be rubbish because it was diplaying the result as ASCII characters. If changed display settings to show hex values instead, it shows the correct values. Could that be the problem in your case as well?

RE: Sending SAADC over BLE?

Filip — Sun, 17 Apr 2016 18:43:04 GMT

Also, the peripheral board with the sensor stops printing out readings after event #135. Is this normal and can I allow it to keep going further?

RE: Sending SAADC over BLE?

Filip — Sun, 17 Apr 2016 18:35:39 GMT

Ok I got my new board in and it is working perfectly over UART so thank you for that! However, when I run "/examples/ble_central/ble_app_uart_c/pca10028" (also tried the pca10031) on my nRF51 Dongle, it spits out garbage for each value. I have identified it is on this code, but am not sure why it is wrong.

for (uint32_t i = 0; i < p_ble_nus_evt->data_len; i++)
       {
             while(app_uart_put( p_ble_nus_evt->p_data[i]) != NRF_SUCCESS);
       }

Thanks so much! This is the last piece and I will be there! :)

RE: Sending SAADC over BLE?

Stefan Birnir Sverrisson — Wed, 13 Apr 2016 08:13:18 GMT

That is safe. That method I usually use to test the ADC is to short the configured AIN pin to GND or VDD.

RE: Sending SAADC over BLE?

Filip — Tue, 12 Apr 2016 17:40:51 GMT

Stefan, You are probably right about the diode being shorted so I just ordered another development board as I want to ensure that I have removed any other variables from the problem. When I get the new board it is safe to connect VDD directly to the AIN0, correct?

RE: Sending SAADC over BLE?

Stefan Birnir Sverrisson — Tue, 12 Apr 2016 16:26:21 GMT

No , this is not normal that you do not get maximum reading on the SAADC. However, you should not expose such high voltage to the GPIO pins. You should not expose more than VDD+0.3V, i.e. supply voltage +0.3V, as stated in the absolute maximum ratings for the nRF52832. Perhaps the ESD diode on GPIO pin P0.02 is shorted already. Try to configure another analog input pin for the SAADC and measure voltage on that pin instead.

RE: Sending SAADC over BLE?

Filip — Mon, 11 Apr 2016 23:36:55 GMT

Wow Stefan this is wonderful! I downloaded the code and ran it, and it is working perfectly! I am going to read through the code thoroughly to understand how you got it to work versus what I had been attempting.

However, I do have one question: the analog results that I am getting are very bad. For instance, running your code gives me values between 20 and 30 for the output and when I directly apply 5V to AIN0/P0.02 it goes up to 587. Shouldn't the range be between about 0 and 1023?

Also, utilizing the circuit diagram here (www.sparkfun.com/.../389) the values don't have a noticeable difference in the example, but when I use an Arduino they do. Is my only option to use larger gains and account for the fact that a lot of noise will always exist?

RE: Sending SAADC over BLE?

Stefan Birnir Sverrisson — Mon, 11 Apr 2016 15:20:25 GMT

Hi Filip

Below is an example which is a ble_app_uart example combined with the SAADC example. It is based on nRF5 SDK 11.0.0 and I have tested it with softdevice S132 2.0.0 and the PCA10040 development board.

ble_app_uart__saadc_timer_driven.zip

The example samples on pin AIN0/P0.02 and outputs the result both on hardware UART and transfers it over BLE via the NUS service. You can adjust the samling rate by adjusting the SAADC_SAMPLE_RATE_DIVIDER constant and you can adjust the size of the SAADC RAM buffer by adjusting the SAADC_SAMPLES_IN_BUFFER constant.

RE: Sending SAADC over BLE?

Filip — Mon, 11 Apr 2016 01:23:03 GMT

I just figured out that changing the timer for the saadc events from Timer 0 to Timer 3 made the UART output not be garbage. However, the UART output goes extremely fast (compared to the plain saadc example) and the value returned is always 16380.