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ADC reading of external resistor sample code.

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Renaud 2025-01-19 15:30:11 +08:00
parent 2ecba6974b
commit efd5cd28c7
1 changed files with 36 additions and 0 deletions
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/* adcext.c -- read external resistor value using ADC */
/* Copyright (c) 2021-2025 Renaud Fivet */
#include <limits.h>
#include <stdio.h>
#include "system.h" /* uptime, yield(), adc_init(), adc_convert() */
#define RREF 10010 /* Rref is 10kOhm, measured @ 10.01 kOhm */
int main( void) {
unsigned last = 0 ;
const unsigned short *calp ; /* TS_CAL, VREFINT_CAL */
/* Initialize ADC and fetch calibration values */
calp = adc_init( 2 | (1 << 17)) ; /* ADC read on GPIOA1 and VREF */
short Vcal = calp[ 1] ; /* VREFINT_CAL */
printf( "factory calibration: %u, %u, %u\n", calp[ 1], calp[ 0], calp[5]) ;
for( ;;)
if( uptime == last)
yield() ;
else {
short Rsample, Vsample ;
last = uptime ;
Vsample = adc_convert() ;
Rsample = adc_convert() ;
printf( "%i, %i, %i, ", Vcal, Vsample, Rsample) ;
int res = Rsample ? RREF * 4095 / Rsample - RREF : INT_MAX ;
Vsample = 3300 * Vcal / Vsample ;
printf( "%i, %i.%i\n", res, Vsample / 1000, Vsample % 1000) ;
}
}
/* end of adcext.c */