saacd scan oversample

RE: saacd scan oversample

ankurt — Thu, 24 Sep 2020 21:40:26 GMT

Correct, your example works well and found out that the problem was in our application, it works well too now. So no issue here, all good 🙂

RE: saacd scan oversample

Jørgen Holmefjord — Thu, 24 Sep 2020 08:02:00 GMT

OK, so you are not able to reproduce this issue with the example from GitHub, without any modifications?

In that case, I would recommend you to post a new ticket where you describe the issue in details, and include the full project and/or how you integrated it into an example.

RE: saacd scan oversample

ankurt — Wed, 23 Sep 2020 21:04:31 GMT

I was running it on nRF52840 with SD enabled and it gets into this situation within 5-10 min every time I try.

RE: saacd scan oversample

Jørgen Holmefjord — Tue, 22 Sep 2020 12:17:55 GMT

Which chip/DK did you run the example on? How long did you run it before getting into this situation?

RE: saacd scan oversample

ankurt — Mon, 21 Sep 2020 01:03:41 GMT

Thanks, I tried example https://github.com/NordicPlayground/nRF52-ADC-examples/blob/master/nrfx_saadc_simple_low_power_app_timer_multichannel_oversample/main.c

But after some time, it stops and seems as if CPU is stuck but not sure where as no s/w application exception is raised. When I pause debugger, it stop at "Unknown function at 0x00025F40".

RE: saacd scan oversample

Jørgen Holmefjord — Fri, 18 Sep 2020 10:56:17 GMT

There are examples available on GitHub, linked from the SDK migration guide: SAADC driver backported from nrfx 2.2.0

I have also implemented some examples in the nRF5 SDK, which I soon will make available in this GitHub repository.

RE: saacd scan oversample

ankurt — Fri, 18 Sep 2020 00:39:02 GMT

I was struggling with similar problem and looks like V2 API is good. But my application is based upon V1 api using nrf drv saadc leagcy layer. If no example, then at least a porting guide/document will be very helpful.

RE: saacd scan oversample

Jørgen Holmefjord — Mon, 24 Aug 2020 08:46:10 GMT

It is not supported in SDK 16. Similar modifications to the ones described above can be added to nrfx_saadc.c.

Scan + burst is supported in SDK 17.0.0 with NRFX_SAADC_API_V2. Unfortunately, there are no examples in the SDK showing the usage of this new driver implementation.

RE: saacd scan oversample

Coder_hope — Mon, 10 Aug 2020 10:51:08 GMT

I am using SDK 15,it this is not supported too,do you figure out this problem?I am using 14bit oversampling, and SAADC_CONFIG_OVERSAMPLE - Sample period is disabled , the noise is not reduced..

RE: saacd scan oversample

ftjandra — Thu, 06 Aug 2020 22:35:39 GMT

Is this now supported in SDK16.0 (scan + burst)? If not, what modifications need to be done and where. I don't think nrf_drv_saadc.c exists anymore.

Thanks.

RE: saacd scan oversample

Jason Hendrix — Wed, 08 Nov 2017 17:58:35 GMT

Thanks Jorgen, that works perfectly for me.

RE: saacd scan oversample

Jørgen Holmefjord — Wed, 08 Nov 2017 12:09:20 GMT

Hi Jason,

As described by Carsten in the thread you are linking, oversample will give correct sampling in scan mode only when burst is enabled for all active channels.

Unfortunately, this is not supported by the SAADC driver in the SDK. It should however be quite simple to add this support if you want to use it. These instructions are for SDK 14.1.0, all changes in nrf_drv_saadc.c:

Add an array called burst to the struct nrf_drv_saadc_cb_t, to keep track of the burst settings for each channel (add between line 93-94):

uint8_t burst[NRF_SAADC_CHANNEL_COUNT];    ///< Burst configurations of SAADC channels.

Add a check to make sure all enabled channels have burst enabled, in nrf_drv_saadc_channel_init() (replace line 314-316):

// Oversampling can be used with only one channel, or if burst is enabled for all active channels.
uint8_t allow_oversample = true;
if(m_cb.active_channels != 0)
{
	for(int i = 0; i < NRF_SAADC_CHANNEL_COUNT; i++)
	{
		if ((m_cb.psel[i].pselp != NRF_SAADC_INPUT_DISABLED) && m_cb.burst[i] != NRF_SAADC_BURST_ENABLED)
		{
			allow_oversample = false;
		}
	}
	if(allow_oversample && p_config->burst == NRF_SAADC_BURST_DISABLED)
	{
		allow_oversample = false;
	}
}
ASSERT((nrf_saadc_oversample_get() == NRF_SAADC_OVERSAMPLE_DISABLED) || allow_oversample);

Store burst setting in struct before initializing the channel in nrf_drv_saadc_channel_init() (add between line 344-345):

m_cb.burst[channel] = p_config->burst;

Clear burst setting in struct when uninitializing channel in nrf_drv_saadc_channel_uninit() (add between line 383-384):

m_cb.burst[channel] = NRF_SAADC_BURST_DISABLED;

I will report this internally, hopefully we can make the driver support this.

Best regards,

Jørgen