SAADC scans only one sample

RE: SAADC scans only one sample

haakonsh — Wed, 02 Oct 2019 11:56:30 GMT

The length of the scan is determined by the number of enabled channels. If you have 2 enabled channels a single triggered SAMPLE task will take one sample from each channel. If your buffer size is larger than 2 you will need to trigger the SAMPLE task enough time to fill the provided buffer, at which point an END event is triggered.

RE: SAADC scans only one sample

Peter.J — Wed, 02 Oct 2019 08:30:52 GMT

Hello Haakonsh,

thanx for your feedback. This I havent understood from the examples. There is not so much difference if I set the buffer size 2 or any multiple of 2 (in my case of 2 channels). Either the buffer is emptied every sample call or after the last sample call all at once.

My understanding was the size of the buffer determines lengthof the scan.

So I should trigger the next scan when the previous one iscompleted. I dont call buffer convert in between. Correct?

peter

RE: SAADC scans only one sample

haakonsh — Wed, 02 Oct 2019 07:59:45 GMT

You need to trigger the sample task twice to fill the buffers now, otherwise, you will never get an END event.

One SAMPLE task will sample all enabled channels once.

RE: SAADC scans only one sample

Peter.J — Tue, 01 Oct 2019 15:03:56 GMT

Hello Haakonsh,

I call

err_code = nrf_drv_saadc_buffer_convert(m_resistivity_measurement_buffer_pool, SAADC_SAMPLES_IN_BUFFER);

where

static nrf_saadc_value_t m_resistivity_measurement_buffer_pool[SAADC_SAMPLES_IN_BUFFER];

and

SAADC_SAMPLES_IN_BUFFER I set 2 resp 4. I scan 2 channels.

I trigger nrf_drv_saadc_sample() once right after the buffer convert call.

peter

RE: SAADC scans only one sample

haakonsh — Tue, 01 Oct 2019 14:46:47 GMT

[quote user="Peter.J"]When I increase size of the buffer to 4 then it gets stuck.[/quote]

I need to know exactly what's changed, how do you increase the buffer size?

[quote user="Peter.J"]I recap that I am running Saadc low power mode as it only triggers scan task software way[/quote]

How many times do you trigger the SAMPLE task?

RE: SAADC scans only one sample

Peter.J — Mon, 30 Sep 2019 23:25:53 GMT

Hello Haakonsh,

I am checking the callback function by setting up a flag when called. I check the flag then outside on upper level.

I stepped into scan investigation again. I used logging level for finding out results of calls.

I am scanning 2 channels. When the buffer size was set 2, "scan" worked. I could see log:

<info> saadc: Function: 233084, buffer length: 2, active channels: 2.
<info> saadc: Function: nrf_drv_saadc_buffer_convert, error code: NRF_SUCCESS.
<debug> app: Saadc init 0 saadc_battery_and_temperature_handler error code: NRF_SUCCESS
<debug> saadc: Event: NRF_SAADC_EVENT_STARTED.
<info> saadc: Function: nrf_drv_saadc_sample, error code: NRF_SUCCESS.
<debug> saadc: Event: NRF_SAADC_EVENT_END.

When I increase size of the buffer to 4 then it gets stuck. The callback is not called as scan is not finished.

I recap that I am running Saadc low power mode as it only triggers scan task software way - when e.g. PPi is not used (see my explanation earlier).

Do you have any idea what I should check?

peter

RE: SAADC scans only one sample

haakonsh — Mon, 30 Sep 2019 14:05:18 GMT

[quote user="Peter.J"]I dont see calibrate to call callback function with NRF_DRV_SAADC_EVT_CALIBRATEDONE event and also any other. [/quote]

That's strange, it should work. How, exactly, do you make sure that you've entered the callback?

[quote user="Peter.J"]Before, all the registers were 0, while after the EVENTS_STARTED 0x100 was 1. Is this according to expectations?[/quote]

I'm not 100% sure the calibration task triggers a started event, but it would not surprise me if it did. If it does not then it means that something else in your application is triggering the start task of the SAADC while you're calibrating.

[quote user="Peter.J"]is nrf_drv_saadc_buffer_convert() not needed for the calibration?[/quote]

Nope.

[quote user="Peter.J"]the calibration is valid for all ADC channels or only for those that are initialiazed? When I init another channel after calibration should i run calibration for those channels again?[/quote]

The calibration is independent of the input channels and is valid for all channels.

RE: SAADC scans only one sample

Peter.J — Mon, 30 Sep 2019 12:44:44 GMT

Hello Haakonsh,

I followed your suggestion: called saadc_calibrate(), no nrf_drv_saadc_buffer_convert calling before that. Abort worked on the first call, as SAADC was idle.

I dont see calibrate to call callback function with NRF_DRV_SAADC_EVT_CALIBRATEDONE event and also any other. I called saadc_get_registers() function right before and after calling saadc_calibrate(), function. Before, all the registers were 0, while after the EVENTS_STARTED 0x100 was 1. Is this according to expectations?

When I added NRF_LOG_DEBUG() print function after the calibration call, the callback was called. As NRF_LOG_DEBUG calls an interrupt I suspect that this helped the callback to be called. I think there is something with interrupt settings not working correctly.

Two additional questions:

- is nrf_drv_saadc_buffer_convert() not needed for the calibration?

- the calibration is valid for all ADC channels or only for those that are initialiazed? When I init another channel after calibration should i run calibration for those channels again?

peter

RE: SAADC scans only one sample

haakonsh — Fri, 27 Sep 2019 08:11:21 GMT

Try this:

ret_code_t saadc_calibrate(void) {
    ret_code_t err_code;

    while(nrf_drv_saadc_is_busy())
    {
        nrf_drv_saadc_abort(); // Abort any SAADC activity, puts the driver in NRF_SAADC_STATE_IDLE. 
    }

    err_code = nrf_drv_saadc_calibrate_offset();
	NRF_LOG_DEBUG("Saadc calibrate %s error code: %s", (uint32_t)__func__, (uint32_t)NRF_LOG_ERROR_STRING_GET(err_code));

    while(nrf_drv_saadc_is_busy())
    { 
        // Wait for calibration to complete
    }
    
    return err_code;
}

NB:
After you've called nrf_drv_saadc_buffer_convert the SAADC driver is in NRF_SAADC_STATE_BUSY as it is waiting for the Sample task to be triggered. The SAADC will be in NRF_SAADC_STATE_BUSY until the buffer has been filled with samples and you've gotten a callback in main.

RE: SAADC scans only one sample

Peter.J — Thu, 26 Sep 2019 00:11:48 GMT

Hello Haakonsh,

I understand that eclipse is not the favorite IDE for the nRF. There is not so much support / up to date. I tried to setup debugger but ended up with the device packages not working. Switching to Segger studio is not an option for me at this stage of the project.

I decided to go other way to get SAADC registers. I implemented a simple function that gets registers values:

void saadc_get_registers(uint32_t * registers) {
	uint32_t * p;

	p =  (uint32_t *)NRF_SAADC_BASE;

	registers[0] = p[0];
	registers[1] = p[1];
	registers[2] = p[2];
	registers[3] = p[3];

	p += 0x100;

	registers[4] = p[0];
	registers[5] = p[1];
	registers[6] = p[2];
	registers[7] = p[3];
	registers[8] = p[4];
	registers[9] = p[5];
}

The register values then I print at other point, on the main level. Please, let me know if this approach is viable.

The other question I would like to ask, is I believe very close related to the SAADC scan. The first thing I am trying to do is calibration. I implemented a simple code:

ret_code_t saadc_calibrate(void) {
    ret_code_t err_code;

    err_code = nrf_drv_saadc_buffer_convert(m_battery_measurement_buffer[0], SAADC_BATTERY_SAMPLE_COUNT); 
	NRF_LOG_DEBUG("Saadc init 0 %s error code: %s", (uint32_t)__func__, (uint32_t)NRF_LOG_ERROR_STRING_GET(err_code));

    err_code = nrf_drv_saadc_buffer_convert(m_battery_measurement_buffer[1], SAADC_BATTERY_SAMPLE_COUNT);
	NRF_LOG_DEBUG("Saadc init 1 %s error code: %s", (uint32_t)__func__, (uint32_t)NRF_LOG_ERROR_STRING_GET(err_code));

    while((err_code = nrf_drv_saadc_calibrate_offset()) != NRF_SUCCESS);
	NRF_LOG_DEBUG("Saadc calibrate %s error code: %s", (uint32_t)__func__, (uint32_t)NRF_LOG_ERROR_STRING_GET(err_code));

    return err_code;
}

The saadc_calibrate() function is called at the beginning of the main, no library is called before (besides log init) in order to avoid any influences.

Surprisingly, I found out that the nrf_drv_saadc_calibrate_offset() always returns NRF_ERROR_BUSY result. I am not sure if that is a result of the buffer convert called before?

My understanding is that if calibration doesnt work then also scan doesnt work. This way I may come to the root cause for scan not working?

Best regards,

peter

RE: SAADC scans only one sample

haakonsh — Wed, 25 Sep 2019 10:33:55 GMT

I don't know Eclipse, but you should be able to view the peripheral registers. Usually the IDE uses the target ARM device's SVD file to create a register map that's easily viewable.

If Eclipse does not have this functionality then I suggest you try Segger Embedded Studios, as we provide our customers with a free license for development on our devices.

RE: SAADC scans only one sample

Peter.J — Tue, 24 Sep 2019 15:09:25 GMT

Eclipse and Segger Jlink.

RE: SAADC scans only one sample

haakonsh — Tue, 24 Sep 2019 14:21:32 GMT

What IDE are you using?

The gist of it is just to halt the CPU after you've started RTC2, and read the state of the SAADC registers in RAM. See Registers for register addresses and their specs.

RE: SAADC scans only one sample

Peter.J — Tue, 24 Sep 2019 13:25:00 GMT

Hello Haakonsh,

can you advise me how to do that? Besides debugging.

Best regards,

peter

RE: SAADC scans only one sample

haakonsh — Mon, 23 Sep 2019 14:39:28 GMT

Hmm, maybe the DONE event interrupt is enabled or something.

Can you capture the state of the SAADC registers after you've initialized and started sampling?

RE: SAADC scans only one sample

Peter.J — Fri, 20 Sep 2019 00:15:22 GMT

Hello Haakonsh,

I tried SAADC_SAMPLES_IN_BUFFER with multiples of 2. Every 2 samples (1 and 1 on each channel) generate callback. I tried PPI and nrf timer driver as the first version (as one of the examples). The behavior was the same - I was getting multiple of callbacks depending on the buffer size. That's the reason that I suspect some SDK config issue.

Best regards, peter

RE: SAADC scans only one sample

haakonsh — Thu, 19 Sep 2019 13:19:43 GMT

What's the value of SAADC_SAMPLES_IN_BUFFER?

RTC0 is used by the SoftDevice and RTC1 is used by the app_timer in various libraries throughout the SDK.

Since you're using the RTC to trigger the sample task I suggest you do it via PPI and not via an interrupt. See the PPI example for how one connects a peripheral event to a task.

RE: SAADC scans only one sample

awneil — Wed, 18 Sep 2019 17:38:24 GMT

RE: SAADC scans only one sample

Peter.J — Wed, 18 Sep 2019 16:43:44 GMT

Hello Haakonsh,

thanx for your feedback. I add relevant pieces of the code:

static nrf_drv_saadc_config_t m_saadc_config =
{
.low_power_mode = true,
.resolution = NRF_SAADC_RESOLUTION_10BIT,
.oversample = NRF_SAADC_OVERSAMPLE_DISABLED,
.interrupt_priority = APP_IRQ_PRIORITY_LOW
};

static nrf_saadc_channel_config_t m_saadc_channel_1_config =
{
.reference = NRF_SAADC_REFERENCE_VDD4,
.gain = NRF_SAADC_GAIN1,
.acq_time = SAADC_SCAN_ACQ_TIME,.// (10 us)
.mode = NRF_SAADC_MODE_DIFFERENTIAL,
.pin_p = ADC_CHANNEL_1_PIN,.
.pin_n = ADC_CHANNEL_2_PIN,
.resistor_p = NRF_SAADC_RESISTOR_DISABLED,
.resistor_n = NRF_SAADC_RESISTOR_DISABLED
};

similarly channel 2, except pins definitions

...

err_code = nrf_drv_saadc_init(&m_saadc_config, saadc_callback);
APP_ERROR_CHECK(err_code);

...

err_code = nrf_drv_saadc_channel_init(1, &m_saadc_channel_1_config);
APP_ERROR_CHECK(err_code);
err_code = nrf_drv_saadc_channel_init(2, &m_saadc_channel_2_config);
APP_ERROR_CHECK(err_code);

err_code = nrf_drv_saadc_buffer_convert(m_measurement_buffer_pool[0], SAADC_SAMPLES_IN_BUFFER);
APP_ERROR_CHECK(err_code);

err_code = nrf_drv_saadc_buffer_convert(m_measurement_buffer_pool[1], SAADC_SAMPLES_IN_BUFFER);
APP_ERROR_CHECK(err_code);

Then in RTC2 timer interrupt handler:

nrf_drv_saadc_sample();

SAADC callback:

void saadc_callback(nrf_drv_saadc_evt_t const * p_event)
{

if (p_event->type == NRF_DRV_SAADC_EVT_DONE)
{ nrf_drv_saadc_buffer_convert(p_event->data.done.p_buffer, SAADC_SAMPLES_IN_BUFFER);

copying scanned data to an array for further processing

I suspect if some of the SDK configuration is correctly set. E.g. I dont have RTC1 enabled as when enabled the compiler gives an error of double definition of IRQ handler (or something similar). RTC1 is responsible for interrupts management, if I am not mistaken?

Best regards,

peter

RE: SAADC scans only one sample

haakonsh — Wed, 18 Sep 2019 09:16:27 GMT

[quote user=""]The channels are configured standard way using nrf_drv_saadc_channel_init() and nrf_drv_saadc_buffer_convert(). I start conversion by calling nrf_drv_saadc_sample() and set low power mode[/quote]

From Prod spec's Analog inputs and channels: "Any one of the available channels can be enabled for the ADC to operate in one-shot mode. If more than one CH[n] is configured, the ADC enters scan mode."

[quote user=""]This I understood to run several scan samples until buffer lasts.[/quote]

From Scan mode: "A channel is considered enabled if CH[n].PSELP is set. If more than one channel, CH[n], is enabled, the ADC enters scan mode.

In scan mode, one SAMPLE task will trigger one conversion per enabled channel."

[quote user=""]I am not doing calibration at this stage, as it requires scan to work.[/quote]

You need to run calibration fairly often if you want accurate results.

I suggest you provide us with the relevant code so that we can see exactly what you've done.