SAADC , BLE

RE: SAADC , BLE

Jørgen Holmefjord — Tue, 08 Mar 2022 18:02:02 GMT

Normally, the USB would cause more noise than external supply. Is the voltage of your external supply stable? Are you using any switching regulators in the supply system?

You can average out the noise by enabling oversampling in the SAADC peripheral, but this will increase the sample time for each result proportionally. Enabling BURST mode will allow you to do the oversampling as fast as possible.

RE: SAADC , BLE

gozde — Sat, 05 Mar 2022 16:01:25 GMT

Hi,

I solved this problem , but my new problem is now, the external power supply create noise on my signal. When i supply nrf with usb , the results are suitable but when i supply the nrf with 3.3V through external power supply pins, the analog signal which i want to convert to digital has noise on it.

What is the reason of that? How can i solve it?

Best Regards.

RE: SAADC , BLE

Jørgen Holmefjord — Thu, 03 Mar 2022 20:53:03 GMT

Hi,

For sending large number of samples, it is better to send the actual raw samples as 16-bit integers, as converting it to/from string will be time-consuming and generate more data over the air.

In an older version of the GitHub example, we actually sent the raw SAADC data over NUS, but too many people got confused when trying to read the received data on phone applications like nRF Toolbox UART. You can use this method, but you need to read the received values as int16_t on the receiver end, and not as string. To be able to achieve 3.3kHz sample interval over BLE, you need to configure quite low connection interval and/or increase the BLE packet length to send more samples in each transfer.

Best regards,
Jørgen