Poll the XADC dedicated analog input VP/VN to sample external signals

zc702_xadc_poll_vpvn.c

#include "xparameters.h"
#include "xadcps.h"
#include "stdio.h"
#include "sleep.h"

/**
 * Return the fractional part of a float as an integer
 */
int fract(float num)
{
	float tmp;

	tmp = num;
	if (num < 0) {
		tmp = -(num);
	}

	return( ((int)((tmp -(float)((int)tmp)) * (1000.0f))));
}

int main(void)
{
	int status;
	XAdcPs xadc;

	u32 raw_data;
	float voltage;

	printf("\r\nPolling XADC dedicated analog input VP/VN...\r\n");

	XAdcPs_Config *cfg = XAdcPs_LookupConfig(XPAR_XADCPS_0_DEVICE_ID);
	if (cfg == NULL)
		goto error;

	status = XAdcPs_CfgInitialize(&xadc, cfg, cfg->BaseAddress);
	if (status != XST_SUCCESS)
		goto error;

	status = XAdcPs_SelfTest(&xadc);
	if (status != XST_SUCCESS)
		goto error;

	/* Configure XADC to "Single Channel Mode", continuous, channel VP/VN, 0-1V range */
	XAdcPs_SetSequencerMode(&xadc, XADCPS_SEQ_MODE_SINGCHAN);
	status = XAdcPs_SetSingleChParams(&xadc,XADCPS_CH_VPVN,FALSE,FALSE,FALSE);
	if (status != XST_SUCCESS)
		goto error;

	/* read value from ADC every sec */
	while (TRUE) {

		raw_data = XAdcPs_GetAdcData(&xadc, XADCPS_CH_VPVN);
		raw_data >>= 4; // 12-bits value is located at MSB, so shift to read it correctly

		voltage = (float)raw_data / (float)0xFFF; // compute voltage value between 0-1V

		xil_printf("VP/VN input = %d mV \t (raw=%d)\r\n", fract(voltage), raw_data);

		sleep(1);
	}

	return XST_SUCCESS;

error:
	printf("Exiting with error code %d!\n", status);
	return XST_FAILURE;
}