RE: SAADC Sampling with a 3-axis Accelerometer

haakonsh — Wed, 01 Aug 2018 11:06:40 GMT

Hey Benjamin, sorry for the late reply.

I've got a hard time following your buffer set-up. The normal way is to just declare a buffer as an array of uint16's :

uint16_t adc_buffer[3];

Set it to zero with a call to memset(&adc_buffer, 0, SAMPLES_IN_BUFFER);

The SAADC will place the 14 bit samples as 16 bit unsigned intergers in a consecutive array of unsigned 16 bit integers. This means that adc_buffer[0] contains the x value, [1] contains the y value, and [2] contains the z value.

Since you're reusing the buffer you need to cache the content between each sample:

declare a uint16_t xyz_buffer;

And copy the adc_buffer into the xyz_buffer in your adc event handler with a call to memcpy(&xyz_buffer, &adc_buffer, SAMPLES_IN_BUFFER);