ADC Conversion using 4096Hz for nRF52832 Chip?

RE: ADC Conversion using 4096Hz for nRF52832 Chip?

Jørgen Holmefjord — Fri, 24 Nov 2017 12:27:09 GMT

You might need to get some better equipment than a multimeter for doing presice measurements of these quickly switching currents. I would recommend the Power Profiler Kit. I did some measurements on the ble_app_uart__saadc_timer_driven__scan_mode code with timer and RTC, and did not see large differences in current (TIMER - RTC). The timer in the example runs on PCLK1M, which gives the timer a run current of 5 µA typical + HFINT Clock run current of 60 µA. The run current of RTC is 0.1 µA typical, pluss run current of LFCLK of 0.25-1 µA. There are some differences here, but compared to the total consumption of the application, this is not the part you should be concerned about. The ~2mA base current of the consumption comes from the EasyDMA current. You should consider if you need such a high sample frequency in your application, or if you could lower this and shut down the SAADC between sampling. This will save you much current.

RE: ADC Conversion using 4096Hz for nRF52832 Chip?

vishal — Fri, 24 Nov 2017 10:23:25 GMT

I measure the current using multi meter which is connected serial of positive power supply. I measure 5.78mA current during advertising only when i reading ADC value at that it goes to 6-7mA with BLE connectivity in android apps. In new RTC code i am not set sampling rate only set frequency and CC value is 32768 and 8. So sir Can you guide me how i can reduce this high current consumption because my device is operate on AA battery cell. For long battery life is important for me. In my new RTC program where i need to define sampling rate, and also How i can control EasyDMA for less current consumption. You saying are upload my main program.

RE: ADC Conversion using 4096Hz for nRF52832 Chip?

Jørgen Holmefjord — Fri, 24 Nov 2017 09:41:11 GMT

How do you measure the current? If 5 mA is your average current consumption with only advertising, this seems quite high. switching to RTC for sampling should not increase your current consumption. Do you have approximately the same sample rate with both setups? The EasyDMA current (~2mA) enabled with the SAADC could be limited by disabling the SAADC between samples, as shown in the low power SAADC example, but with your samplerate, you might not gain much on this either. Could you upload your applications for debugging?

RE: ADC Conversion using 4096Hz for nRF52832 Chip?

vishal — Thu, 23 Nov 2017 10:39:59 GMT

Thanks you so much Jorgen, Now my program is working as per you refer me, But problem is current consumption. In my old program using Timer peripheral ADC the current consumption is 5mA with BLE advertising. But now when i implement my code into RTC over PPI current consumption is 5.78mA. If i use RTC the current consumption it will reduce because RTC is low power consumption instead of timer. Can you tell why current consumption increase in my device. My device is operate on battery so to reduce current consumption is important for me.

RE: ADC Conversion using 4096Hz for nRF52832 Chip?

Jørgen Holmefjord — Thu, 23 Nov 2017 08:45:35 GMT

I don't know how you have setup RTC, but you should make sure you do not enable interrupt if you want to trigger the sampling through PPI. You also need to clear the RTC after getting the compare event. This can also be done using PPI. I will edit my answer above with a working main.c file for ble_app_uart__saadc_timer_driven__scan_mode that implement sampling using RTC over PPI. Note that you need to include the nrf_drv_rtc.c source file, and enable RTC in sdk_config.h.

RE: ADC Conversion using 4096Hz for nRF52832 Chip?

vishal — Thu, 23 Nov 2017 06:20:39 GMT

Thanks Jorgen, As per you told me i changed the function is

uint32_t timer_compare_event_addr = rf_drv_rtc_event_address_get(&rtc,NRF_RTC_EVENT_COMPARE_0);

it give error for &m_timer unresolve So i uncomment in my code is

static const nrf_drv_timer_t   m_timer = NRF_DRV_TIMER_INSTANCE(3);

but it for timer peripheral. NRF_Timer frequency as sampling rate but this all parameter is use for timer peripheral is it write. What should i do for other parameter like NRF timer frequency sampling rate etc. If i set same as it is and sampling rate set is 125ms. Then i have test this function but it consume lots power it near about 5.56mA while BLE broadcasting. When transmitting adc value to android app at that time peak current is 7.2mA. Why this more power consume?

RE: ADC Conversion using 4096Hz for nRF52832 Chip?

Jørgen Holmefjord — Wed, 22 Nov 2017 15:39:21 GMT

PPI sampling with RTC is setup very similar to PPI sampling with TIMER, if you use the drivers in the SDK. You only need to change the function that get the address of the compare event from timer, into the funtion that get the compare event from RTC:

uint32_t timer_compare_event_addr = nrf_drv_rtc_event_address_get(&rtc,NRF_RTC_EVENT_COMPARE_0);

RE: ADC Conversion using 4096Hz for nRF52832 Chip?

vishal — Wed, 22 Nov 2017 12:51:28 GMT

Hi sir, Can you tell me how i trigger sample though ppi on RTC. In my last program i am triggering sample through PPI on Timer peripheral. Where i need to changes in saadc_sampling_event_init(void) function for controlling PPI on RTC. Thanks......

RE: ADC Conversion using 4096Hz for nRF52832 Chip?

vishal — Tue, 21 Nov 2017 15:02:23 GMT

I check in my sdk_config.h RTC0 is not enable RTC2 is enabled, now when i remove lfclk_config(void) function device is advertising and also connect with my phone. But when i sent command for start saadc my ADC value is not received in my apps, means no any data sent from nordic to UART. As per you refer me this above example in this no any PPI channel use. Can you tell me how i trigger PPI on RTC. In my code i use saadc_sampling_event_enable(); in main. my application is read 3-axis accelerator analog value one by one channel. Thanks sir......

RE: ADC Conversion using 4096Hz for nRF52832 Chip?

Jørgen Holmefjord — Tue, 21 Nov 2017 12:28:13 GMT

Make sure you are not using RTC0, as this is used by the softdevice. You can chose which RTC is enabled in sdk_config.h. You do not need to initialize the lfclock when using the softdevice, as the softdevice already handles this.

RE: ADC Conversion using 4096Hz for nRF52832 Chip?

vishal — Tue, 21 Nov 2017 12:00:18 GMT

Yes i debugging my code and it return error code is 133 can you tell me what is meaning of this error code. This error is in static void lfclk_config(void) function. I am using sdk 13.1 and soft device is S132 for nRF52832 using eclipse IDE. can you suggest me what should i do.. Thanks...for your quick reply.

RE: ADC Conversion using 4096Hz for nRF52832 Chip?

Jørgen Holmefjord — Tue, 21 Nov 2017 11:47:55 GMT

Are you using the correct softdevice/SDK version for the example? Have you tried debugging, to see if any function calls return error codes?

RE: ADC Conversion using 4096Hz for nRF52832 Chip?

vishal — Tue, 21 Nov 2017 09:50:10 GMT

Thanks sir for you valuable suggestion.. I changes in my program as per the given in above example using RTC. but now problem coming is when i upload this new program my board is not advertising. So i am unable to connect. I am using ble_app_uart__saadc_timer_driven__scan_mode this example. Can you tell me where exactly i need to change for RTC. Thanks....

RE: ADC Conversion using 4096Hz for nRF52832 Chip?

Jørgen Holmefjord — Tue, 14 Nov 2017 14:15:10 GMT

You are not using RTC in that code, you are using TIMER peripheral. Please have a look at this example on how to use RTC and PPI for triggering SAADC sampling. If you set the symbol RTC_FREQUENCY in main.c to 32768, the example should sample at 4096 Hz. Note that you should increase the calibration interval, or disable calibration for such a high sample rate.

RE: ADC Conversion using 4096Hz for nRF52832 Chip?

vishal — Tue, 14 Nov 2017 13:34:08 GMT

Please sir tell me what should i do for achieving 4096Hz sampling frequency. you told me set CC value is 8, but my cc value is microsecond you said me this value is millisecond or other.

Thanks for your suggestion.

RE: ADC Conversion using 4096Hz for nRF52832 Chip?

vishal — Tue, 14 Nov 2017 13:30:05 GMT

Hi sir, I trigger sample through PPI on an RTC, but it achieved 3900Hz. The following have my program function in saadc sampling event init:

nrf_drv_timer_config_t timer_config = NRF_DRV_TIMER_DEFAULT_CONFIG;
timer_config.frequency = NRF_TIMER_FREQ_31250Hz;
err_code = nrf_drv_timer_init(&m_timer, &timer_config, timer_handler);
APP_ERROR_CHECK(err_code);
/* setup m_timer for compare event */
uint32_t ticks = nrf_drv_timer_us_to_ticks(&m_timer,SAADC_SAMPLE_RATE);
nrf_drv_timer_extended_compare(&m_timer, NRF_TIMER_CC_CHANNEL0, ticks, NRF_TIMER_SHORT_COMPARE0_CLEAR_MASK, false);
nrf_drv_timer_enable(&m_timer);

uint32_t timer_compare_event_addr = nrf_drv_timer_compare_event_address_get(&m_timer, NRF_TIMER_CC_CHANNEL0);

and in this function CC value is as per the following: Sampling Rate = 256us

m_timer = NRF_DRV_TIMER_INSTANCE(3);

RE: ADC Conversion using 4096Hz for nRF52832 Chip?

Jørgen Holmefjord — Tue, 10 Oct 2017 08:33:19 GMT

Hi,

If you trigger sampling through PPI on an RTC event, it should be possible to achieve 4096 Hz. The RTC runs at 32.768 kHz, and a CC value of 8 should give you your desired frequency. If you are triggering sampling from interrupt event, the softdevice might delay sampling if higher priority events occurs, giving you a lower sample rate than expected.

Note this issue if you are triggering sampling through PPI, and have multiple SAADC channels enabled.

[EDIT]: Added main.c file that implements sampling triggered by RTC over PPI in ble_app_uart__saadc_timer_driven__scan_mode example: main.c

Best regards,

Jørgen