Problem with SAADC examples for audio sampling

RE: Problem with SAADC examples for audio sampling

stefano.luna — Thu, 27 Apr 2017 09:18:19 GMT

Thank You Jørgen, your information were very useful.

RE: Problem with SAADC examples for audio sampling

Jørgen Holmefjord — Tue, 25 Apr 2017 12:05:03 GMT

You can try to increase the UART string length NRF_LOG_BACKEND_MAX_STRING_LENGTH and buffer size if using NRF_LOG_DEFERRED, NRF_LOG_DEFERRED_BUFSIZE. You can also try with a higher baudrate for the UART communication, NRF_LOG_BACKEND_SERIAL_UART_BAUDRATE. All these parameters can be configured in sdk_config.h. You can also try using RTT as the backend for NRF_LOG, and use J-Link RTT Viewer to view the samples.

RE: Problem with SAADC examples for audio sampling

stefano.luna — Tue, 25 Apr 2017 10:59:31 GMT

Hi, thanks for your support. I think that the overflow is from the logging to UART, and it's good to hear. I fixed the sampling frequency to 50kHz (sampling time 20us) with nrf_drv_timer_us_to_ticks and I tried to run again the example with a buffer of 64 samples, obtaining this from the terminal: The first event has correctly 64 samples but the second one has only 60 followed by overflows. How can we fix the UART overflow problem?

RE: Problem with SAADC examples for audio sampling

Jørgen Holmefjord — Tue, 25 Apr 2017 07:38:40 GMT

What exactly do you mean by that you get overflow? Do the logging to UART overflow, or is there some issue with the sampling? There is also a function nrf_drv_timer_us_to_ticks, which can be used for higher sample rates. You can also set the ticks parameter manually, by calculating the desired ticks from the frequency of the timer (16 MHz by default). You can find the documentation of the TIMER peripheral here.