ADC - select pins

embedded_eng_ — Wed, 14 Jul 2021 07:21:22 GMT

Hi,

I have a LPC55S16-EVK, and I'm using MCUXpresso IDE.

I'm working on a project that is based on lpcxpresso55s16_dev_composite_cdc_msc_bm demo, And I'm trying to add ADC support.

I want to use pin 11 (ADC0 Channel 3B) and pin 23 (ADC0 Channel 3A).

I soldered pin 11 and pin 23 to external wires that are connected to 2 terminals of the same resistor.

My goal is to measure the voltage drop on this resistor(difference between these 2 pins).

I configured the pins using config tool

I configured the clock

Peripheral:

And I copied the driver files (fsl_lpadc.*) from another demo to my drivers directory.

I tried to copy the main function code to my main function (just the relevant parts), and the code compiles, but the reads are wrong.

I read "46164" when I should read GND value.

I guess the problem is that I'm not selecting the correct pin.

How can I select, for example, pin 23 (ADC0 Channel 3A)?

#define DEMO_LPADC_BASE ADC0 #define DEMO_LPADC_USER_CHANNEL 3U #define DEMO_LPADC_USER_CMDID 1U

Re: ADC - select pins

Alice_Yang — Wed, 14 Jul 2021 09:41:58 GMT

Hello ,

About ADC channel and 16 bit resolution, you can config in "Conversion commands configuration" :

If can't get data, recommend first use ADC demo under SDK to test, and select and connect the right pin.

Alice

embedded_eng_ — Wed, 14 Jul 2021 14:04:45 GMT

Thanks