SAADC Scan Mode

RE: SAADC Scan Mode

KingKarl237 — Mon, 20 Jun 2016 09:56:41 GMT

I think there are several problems.

check SAMPLES_IN_BUFFER mus be equal to the number of channels or higher.
Which 2 examples are you talking about? my code and the Code from the SDK?
nrf_drv_saadc_buffer_convert is called inside of the callback, so one time with pool 0 and one time with pool 1. Oh i realised your problem. m_buffer_pool has just 2 elements. Thats for get ready the next buffer inside of the callback. the number of channels is used in Samples_in_Buffer.

RE: SAADC Scan Mode

Inspectron — Mon, 20 Jun 2016 08:55:15 GMT

Why we have to call nrf_drv_saadc_buffer_convert(m_buffer_pool[],SAMPLES_IN_BUFFER); only for m_buffer_pool 0 and 1 but not for 2?

RE: SAADC Scan Mode

Inspectron — Mon, 20 Jun 2016 08:17:00 GMT

@Kingkarl237: With this example I will never get into the saadc_callback handler. Do I have to set some settings? Because with the peripheral example from SDK 11.0 I will get into the saadc_callback handler. UPDATE: With 2 channels its working. But with 3 not.

RE: SAADC Scan Mode

KingKarl237 — Mon, 20 Jun 2016 06:22:28 GMT

@Inspectron: The problem described in the Question is fixed in SDK 11. The additional Question in the Comments was caused by a Copy&Paste-Failure. The Example i used is the SAADC Example in the Peripheral Folder, you just have to add the additional ADC-Channels.

RE: SAADC Scan Mode

Inspectron — Sun, 19 Jun 2016 17:13:35 GMT

Is this now fixxed? I would like to use the scan mode and I have SDK 11.0. And is there an example? I have 3 GPIO which I need to measure.

RE: SAADC Scan Mode

KingKarl237 — Wed, 18 May 2016 13:54:16 GMT

Oh no! It was a Copy & Paste Error -.- Thank you very much.

RE: SAADC Scan Mode

Ole Bauck — Wed, 18 May 2016 13:14:03 GMT

I have also tested on PCA10036 and it does not seem like there is any issues with this board.

RE: SAADC Scan Mode

Ole Bauck — Wed, 18 May 2016 13:13:04 GMT

AIN3 is also used by CTS signal in uart, so I would advise you to not use that, use for example AIN4 instead. Channel_3_config is not configured, you are configuring channel_0_config, so channel_3_config will be all zero when you init channel 3.

I was testing on PCA10040 v0.9.0 which uses engineering B chip (see here). I noticed I said wrong in the answer, I will update this.

RE: SAADC Scan Mode

KingKarl237 — Tue, 17 May 2016 07:00:39 GMT

Here i have used the SAADC Example.

Behaviour here is:

AIN1 and AIN2: normal AIN0: doesnt work AIN3: Applys to AIN3 and AIN0. Tested on the pca 10036.

RE: SAADC Scan Mode

Ole Bauck — Fri, 13 May 2016 13:45:12 GMT

I just tested with 4 channels and it works like it should. Can you send me the code you are using (in a c file, not in the comment)?

RE: SAADC Scan Mode

KingKarl237 — Thu, 12 May 2016 07:13:56 GMT

Thanks that solved the problem. But in the meanwhile i upgraded to SD 132v2 and SDK 11 and now i want to sample 4 channels and i have the same Problem. Sampling 3 channels worked. The Code is basically the same like above, just initialising 4 channels and having now SAMPLES_IN_BUFFER = 4; Are the channels limited to 3? nrf_drv_saadc_channel_init gives NRF_SUCCESS . I start the sampling simply with nrf_drv_saadc_sample(); every 10ms.

Thank you

RE: SAADC Scan Mode

Ole Bauck — Mon, 22 Feb 2016 15:47:35 GMT

The values should come in the channel order (initiated with nrf_drv_saadc_channel_init(uint8_t channel, ...)). If SAMPLES_IN_BUFFER is 6 you will get: ch0, ch1, ch2, ch0, ch1, ch2.

SDK 11.0.0-2.alpha has a bug that seems to be present if the array size is equal to the number of channels or a multiple of the size. The reason for this bug is that the engineering A chip (PCA10036) did not have the scan mode in hardware, so the scanning was done manually.

The bug is fixed (I just tested it) in the next version of the SDK which should be out very soon. For now you can set SAMPLES_IN_BUFFER to be larger than the number of channels.