SAADC Limit Disabled Value

RE: SAADC Limit Disabled Value

Jørgen Holmefjord — Wed, 29 Jul 2020 09:09:01 GMT

Hi,

There is a not about this in the known issues section in the release notes for SDK 17:

*** Known Issues
****************

** Drivers and libraries **

- The SAADC driver (from nrfx 1.8.x) does not handle detection limits 'high' and 'low'
  correctly if SAADC resolution is greater than 10 bits.
  SAADC driver ported from nrfx 2.2.x is not affected by this.

RE: SAADC Limit Disabled Value

Anne van Rossum — Wed, 29 Jul 2020 08:38:57 GMT

In the newest SDK (https://infocenter.nordicsemi.com/index.jsp?topic=%2Fsdk_nrf5_v17.0.0%2Fgroup__nrfx__saadc.html&anchor=ga173d0e9cf60be60d50680180a5d82f83) there are still the same defines:

#define 	NRFX_SAADC_LIMITH_DISABLED   (2047)
 	Value to be set as high limit to disable limit detection.
 
#define 	NRFX_SAADC_LIMITL_DISABLED   (-2048)
 	Value to be set as low limit to disable limit detection.

As if they are true for any ADC configuration...

RE: SAADC Limit Disabled Value

Jørgen Holmefjord — Thu, 20 Apr 2017 11:54:08 GMT

Sorry, I see this is not the way the implementation of limit_set in the driver works. I edited my above comment to avoid confusion. I did however try to increase the defines, and limits seems to work fine.

RE: SAADC Limit Disabled Value

WestCoastDaz — Wed, 19 Apr 2017 15:54:23 GMT

Jorgen,

Thanks for taking the time to reply and for looking into this issue. I'm not sure that I understand your last statement "You should not need higher values for 12-bits though, as 2047 - (-2048) gives 4095 (2^12-1)." If a channel is configured as single ended, with 12bits of resolution, then my maximum count value will be 4095 which is over the maximum limit of 2047.

Thanks, Darren

RE: SAADC Limit Disabled Value

Jørgen Holmefjord — Wed, 19 Apr 2017 10:37:39 GMT

I'm not sure about why this is not set acording to product specifications, but it might be leftovers from an old chip version or version of the product specifications. I will check with the driver developer when he is back next week.

RE: SAADC Limit Disabled Value

WestCoastDaz — Mon, 17 Apr 2017 22:15:49 GMT

Nordic team, Any update on this?

Thanks, Darren