working with 2 saadc configurations does not work

[ziv123]

hello Nordic

i am working with nrf52840, sdk 16.0 

i am building my project over the peripheral app_ble_blinky example 

i whish to have 2 seprate configs for saadc

i call the following init function twice (with 2 different saadc_configs (different naming as well) ):

err_code = nrf_drv_saadc_init(&saadc_config, saadc_sample_event_handler);
    APP_ERROR_CHECK(err_code);

it does not seem to be working.. is there a way to initialize 2 saadc configs

best regards

Ziv

[haakonsh]

No, you have to uninit the driver beforehand. 

What is it that you are trying to do exactly?

[ziv123]

haakonsh said:

No, you have to uninit the driver beforehand.

ok .. i found out that saadc has bass address in the instantiation table, so to my understanding there can be only one operational 'nrf_drv_saadc_config_t' at a time, so it brings the question of how is it possible to read all the AIN0-7 channels when one instance can have only 4 channels if i am not wrong.

anyway, so i configure one 'nrf_drv_saadc_config_t' lets call 1_saadc_config and configure a second 'nrf_drv_saadc_config_t' 2_saadc_config,

then i call for nrf_drv_saadc_init(&1_saadc_config,... some handler)

then when sampling is done i call nrf_dev_saadc_uninit();

then i call for nrf_drv_saadc_init(&2_saadc_config, .. some other handler)

and when sampling is done i call nrf_drv_saadc_uninit();

i do not re-init the channel or try to convert the buffers again

i did not test it yet but i hope you can concur the above logic

haakonsh said:

What is it that you are trying to do exactly?

i need to read 2 analog inputs, each at a different time in the program's flow, so there is no collision there. each analog read requires different configurations in resolution and oversampling. 

hope to read from you soon

best regards

Ziv

[haakonsh]

ziv123 said:

so it brings the question of how is it possible to read all the AIN0-7 channels when one instance can have only 4 channels if i am not wrong.

Why do you believe that? It's not true, the saadc driver has access to all the channels. 

ziv123 said:

i need to read 2 analog inputs, each at a different time in the program's flow, so there is no collision there. each analog read requires different configurations in resolution and oversampling. 

 Yeah that's a bit tricky, you'll have to uninit and re-init the saadc driver each time to change the resolution/oversample configuration. You'll also need to change the buffers each time you sample.

I suggest you use the highest resolution + oversample of the two settings and use it for both channels, in addition to sampling both channels at once, then ignore the samples you don't need. 

What exactly are your saadc configurations and sample rate? 

[ziv123]

haakonsh said:

I suggest you use the highest resolution + oversample of the two settings and use it for both channels, in addition to sampling both channels at once, then ignore the samples you don't need.

with one saadc config i sample 3 channels, i can't use ovesampel with this channels cause oversample does ch1 sampel 1to ch1 sample n and then goes to ch2 sample 1 up to ch2 sample n and so on .. i need better accuracy between the channels sampels so ch1 is sampeld once, then ch2 then ch3 and then repeat for the next sample, i sample each channel 4 times .. my sample rate is 32KHz, so 12 samples there without oversampling and in 14 bit resolution

the other saadc config is for one channel and i need only one read every some relatively long time , and 10 bit resulotion is enough, pluse i measure it only after i finish with all the other adc reads also i give some frequency piout to the device before reading this one channel 

and eventualy i put the program to system on sleep mode so i am going to stop sampling and maybe cut the power to saadc driver anyway

so to sum:

what do i requier in order to re-init the saadc, why do i need to reconfigure the buffers and channels if i use 2 different saadc config in every init ?

[haakonsh]

ziv123 said:

why do i need to reconfigure the buffers and channels if i use 2 different saadc config in every init ?

 In your case it seems like you will be done with processing the saadc buffers before you need to re-configure the saadc, in that case you don't need to reconfigure the buffers. 

Just use the uninit and inint functions and you should be fine.