DOUBT IN SAADC EXAMPLE FROM SDK V 14.2.0

RE: DOUBT IN SAADC EXAMPLE FROM SDK V 14.2.0

NANDHU — Thu, 11 Jul 2019 09:12:36 GMT

Thanks a lot i got good idea about saadc now

RE: DOUBT IN SAADC EXAMPLE FROM SDK V 14.2.0

Håkon Alseth — Thu, 11 Jul 2019 09:08:50 GMT

Hi,

As explained earlier, a SAADC conversion is done when you get the callback function with p_evt->type == NRF_DRV_SAADC_EVT_DONE.

As for app_timer, take a project that it matching your usecase, for instance; if you are using the Softdevice, use one of the examples in ble_peripheral/ folder as a template, then add the functionality you need.

Kind regards,

Håkon

RE: DOUBT IN SAADC EXAMPLE FROM SDK V 14.2.0

NANDHU — Thu, 11 Jul 2019 06:16:35 GMT

HI ,

THIS THERE ANY WAY TO INCLUDE app_timer.c and app_timer.h FILES TO NORDIC saadc EXAMPLE

RE: DOUBT IN SAADC EXAMPLE FROM SDK V 14.2.0

NANDHU — Wed, 10 Jul 2019 12:43:36 GMT

Thanks Hakon now all issues was solved ,now all the five values are almost equal and also its varying according to the voltage variation from the power supply .

Now i needed your help to implement the adc to our custom application.

I ready told you that, what's my approach is.

I decided to call the saadc functions for starting the saadc sampling i.e nrf_drv_saadc_sample and for read the adc result i.e nrf_drv_saadc_buffer_convert inside the timer handler function.
But the problem that . How can i verify that the adc conversion is finished or not .Is there any function for that ?

RE: DOUBT IN SAADC EXAMPLE FROM SDK V 14.2.0

NANDHU — Wed, 10 Jul 2019 12:11:00 GMT

Hakon thanks a lot . I will try it and get back to you soon .

RE: DOUBT IN SAADC EXAMPLE FROM SDK V 14.2.0

Håkon Alseth — Wed, 10 Jul 2019 12:07:47 GMT

Connect the negative to GND on the devkit.

Never go over "VDD_NRF" (3V on the DK) on the ADC input, and do not reverse the polarity of your input voltage, as then you exceed the maximum ratings given in the datasheet for the nRF52832.

Kind regards,

Håkon

RE: DOUBT IN SAADC EXAMPLE FROM SDK V 14.2.0

NANDHU — Wed, 10 Jul 2019 11:38:46 GMT

[quote user="hkn"]where to connect this on the development kit?[/quote]

yes,

Actually i want to known ,

where i wanted to connect the negative terminal of the power supply on development kit.

RE: DOUBT IN SAADC EXAMPLE FROM SDK V 14.2.0

Håkon Alseth — Wed, 10 Jul 2019 11:36:46 GMT

Please take the time to post your questions with more detail and try to include as much details regarding your issue and test setup as possible, so that I can get a good overview of the issue and then can provide as efficient support as possible.

Do I understand you correct when you are asking where to place the "GND terminal" from your DC power supply, and where to connect this on the development kit?

Kind regards,

Håkon

RE: DOUBT IN SAADC EXAMPLE FROM SDK V 14.2.0

NANDHU — Wed, 10 Jul 2019 11:20:45 GMT

I already told you that i connect a 1v dc (using DC power supply)to p0.02 in DK for testing saadc example .

I only connect the positive terminal power supply to DK pin p0.02 .Is i needed to connect the negative terminal of the power supply to the DK . If i want to connect the negative terminal of power supply to DK where i wanted to connect it, to the ground or some where else?

RE: DOUBT IN SAADC EXAMPLE FROM SDK V 14.2.0

Håkon Alseth — Wed, 10 Jul 2019 11:01:07 GMT

An ADC samples any type of analog signal, DC or AC. I would recommend that you read up on ADC in general if this is new territory for you.

RE: DOUBT IN SAADC EXAMPLE FROM SDK V 14.2.0

NANDHU — Wed, 10 Jul 2019 10:50:36 GMT

So your are saying, even though a dc voltage is connected to an adc channel there will be a result in adc buffer after adc conversion ? Am i right ?

RE: DOUBT IN SAADC EXAMPLE FROM SDK V 14.2.0

Håkon Alseth — Wed, 10 Jul 2019 10:37:51 GMT

Depends on your settings. I'll give you an example.

Gain = 1/6

Reference = internal 0.6V

Input = 2V.

Resolution = 10 bit.

I would then expect the input range to be:

0.6V / (1/6) = 3.6V (ie: from GND to 3.6V)

Given 10 bit resolution (2^10), 2V would be in this ballpark:

2/3.6 * 1023 = ~568 decimal.

Kind regards,

Håkon

RE: DOUBT IN SAADC EXAMPLE FROM SDK V 14.2.0

NANDHU — Wed, 10 Jul 2019 08:56:48 GMT

I need one clarification .

If we connect a 1V dc to p0.02 pin .what will be the output after adc convertion ?. ADC convertion takeplace or not?

RE: DOUBT IN SAADC EXAMPLE FROM SDK V 14.2.0

Håkon Alseth — Wed, 10 Jul 2019 08:48:47 GMT

That is to be expected, as your analog signal might have ripple on it, and in addition; the SAADC peripheral has an overall accuracy of a given set of LSBits. meaning that if you expect the ideal ADC to give you 1024 with an ideal input signal, you should assume that this value will have a +/- of x amount of LSB in a real-life scenario.

You can read more about ADCs here: https://en.wikipedia.org/wiki/Analog-to-digital_converter#Quantization_error

RE: DOUBT IN SAADC EXAMPLE FROM SDK V 14.2.0

NANDHU — Wed, 10 Jul 2019 08:38:34 GMT

Actually i tried it .

I connect a 1v to p0.02 pin in development kit using dc power supply .But when i debugged it ,in the debug terminal the 5 values are different. why?

RE: DOUBT IN SAADC EXAMPLE FROM SDK V 14.2.0

Håkon Alseth — Wed, 10 Jul 2019 08:33:04 GMT

What I recommend is that you try it out and see how it behaves.

See if you can convert the digital number back to an analog value to see if it matches your input voltage.

Kind regards,

Håkon

RE: DOUBT IN SAADC EXAMPLE FROM SDK V 14.2.0

NANDHU — Wed, 10 Jul 2019 04:23:57 GMT

Suppose if we connect a 1V to the AIN0 i.e in p0.02 ,then what will be the 5 values getting from the buffer is it same or different?

RE: DOUBT IN SAADC EXAMPLE FROM SDK V 14.2.0

Håkon Alseth — Tue, 09 Jul 2019 12:22:35 GMT

If there's no load, it will float. You can then sample anything from min. to max.

RE: DOUBT IN SAADC EXAMPLE FROM SDK V 14.2.0

NANDHU — Tue, 09 Jul 2019 12:18:35 GMT

HI ,

In Nordic "saadc" application there is only one channel is configured AIN0 and each time 5 different values are getting from buffer but, if there is no input connected to adc channel ,then who the values are changeing ?

RE: DOUBT IN SAADC EXAMPLE FROM SDK V 14.2.0

Håkon Alseth — Tue, 09 Jul 2019 11:54:21 GMT

As long as you use an app_timer instance (and not a highspeed TIMER, as these draw more current), I do not see any issues.

Kind regards,

Håkon

RE: DOUBT IN SAADC EXAMPLE FROM SDK V 14.2.0

NANDHU — Tue, 09 Jul 2019 11:40:47 GMT

Hi Hakon ,

Thanks a lot .

Now i got a better clarity of Nordic "saadc" example.

Now i want implement this saadc into our application code. i already told you that we are developing 2d -3d comp mouse and we are using nRF5_SDK_14.2.0_17b948a "ble_app_hids_mouse" application.we modified this application with our own needs.
I decided to implement adc functionality into our application using TIMER and SAADC module only not using not using PPI.
Way of working is like below.

First we will initialize the TIMER and SAADC .
TIMER is initialized in such a way that ,it will generate an event at every 1 min i.e the execution will enter into the "timer handler function"every 1 min repeatedly.
Then inside this "timer handler function" i will call the saadc functions for starting the saadc sampling i.e nrf_drv_saadc_sample and for read the adc result i.e nrf_drv_saadc_buffer_convert
After reading the adc data then corresponding led will turn on if the adc result is less than a particular level.

IS THERE ANY ISSUE WITH MY APPROACH ? IF THERE IS ANY CHANGE NEED PLEASE TELL ME.

RE: DOUBT IN SAADC EXAMPLE FROM SDK V 14.2.0

Håkon Alseth — Tue, 09 Jul 2019 11:04:17 GMT

Hi,

[quote user="NANDHU NAKULAN"]Is this change make any issues in adc convertion?[/quote]

There shouldn't be any issues.

You only provide one buffer, then it will always provide the same RAM pointer into the SAADC peripheral.

Kind regards,

Håkon

RE: DOUBT IN SAADC EXAMPLE FROM SDK V 14.2.0

NANDHU — Tue, 09 Jul 2019 10:58:33 GMT

HI ,

Suppose i declared a normal array instead of 2D

i e "static nrf_saadc_value_t m_buffer_pool[5];"

and only one buffer assign .i.e please look below screen short

what will happenes. Is this change make any issues in adc convertion?

RE: DOUBT IN SAADC EXAMPLE FROM SDK V 14.2.0

Håkon Alseth — Tue, 09 Jul 2019 10:49:03 GMT

The saadc driver has support for handling two buffers.

The _END event will then alternate between m_buffer_pool[0] and m_buffer_pool[1]. You can look at this by entering debug mode and placing a breakpoint in that callback.

Kind regards,

Håkon

RE: DOUBT IN SAADC EXAMPLE FROM SDK V 14.2.0

NANDHU — Tue, 09 Jul 2019 10:18:50 GMT

HI ,

Thanks

My next doubts.

why Nordic using 2D array as buffer instead of normal array . "static nrf_saadc_value_t m_buffer_pool[2][SAMPLES_IN_BUFFER];"
why Nordic assigning the buffer 2 times in "saadc_init " function ? Is the first time assigning is enough?