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Hello Everyone!
Observing the voltage on the variable resistor with a properly calibrated multimeter gives different value, as the one detected by the AD in the controller, and it is not a constant offset, neither seems to be a DC-gain error. I've made some measurements:
| Multimeter voltage [V] | ADC counter value [1] | ADC voltage [V] | Multimeter voltage - ADC voltage difference [V] |
| 2.9999 | 897 | 2.89072275 | 0.10917725 |
|
2.0002 |
574 | 1.84980464 | 0.15039536 |
| 1.0001 | 290 | 0.934570313 | 0.065529687 |
What can cause the difference and how could I solve it or minimize it down below 0.01? Tried it with and without the calibration functions, even tried to set it to a 12-bit ADC, neither of them helped. Thanks in advance for your reply.
I include the code, too:
/* USER CODE BEGIN (0) */
/* USER CODE END */
/* Include Files */
#include "HL_sys_common.h"
/* USER CODE BEGIN (1) */
#include "HL_esm.h"
#include "HL_adc.h"
#include "HL_gio.h"
adcData_t adc_data[1];
void wait(uint32 time);
/* USER CODE END */
/* USER CODE BEGIN (2) */
/* USER CODE END */
int main(void)
{
/* USER CODE BEGIN (3) */
uint32 ch_count=0;
uint32 id =0;
uint32 value =0;
float voltage = 0, valuefloat = 0;
/* initialize gio */
gioInit();
gioSetDirection(gioPORTB, 1);
/* initialize sci/sci-lin : even parity , 2 stop bits */
sciInit();
/* initialize ADC */
/* Group1 -> Channel 0 and 1 */
/* HW trigger trigger source as GIOB Pin 0 */
adcInit();
adcCalibration(adcREG1);
adcMidPointCalibration(adcREG1);
/* start adc conversion */
adcStartConversion(adcREG1,adcGROUP1);
while(1) /* ... continue forever */
{
/* trigger using gio port b, pin 0 */
gioSetBit(gioPORTB, 0, 1);
/* ... wait and read the conversion count */
while((adcIsConversionComplete(adcREG1,adcGROUP1))==0);
ch_count = adcGetData(adcREG1, adcGROUP1,&adc_data[0]);
ch_count = ch_count;
id = adc_data[0].id;
value = adc_data[0].value;
gioSetBit(gioPORTB, 0, 0);
voltage = ((float)value / 1024) * 3.3;
wait(0xFFFFF);
};
/* USER CODE END */
return 0;
}
/* USER CODE BEGIN (4) */
void wait(uint32 time)
{
while(time){time--;};
}
/* USER CODE END */
