I have question about ADC reference voltage monitoring.
MCU : S32K144
Basically VREFH pin connected to vdd(5V)
I have tested that lower the vdd voltage to 4.8V from 5V.
I think that read value should be different in 5V, 4.8V. But I read always 4095 value about ADC reference voltage (variable name : nAdCodeVdd) in both 5V with 4.8V
ADC register setting & implement code as following :
void main(void)
{
for(;;)
{
task 10ms :
Vref_Measure();
Vref_GetValue(nAdCodeVdd);
}
}
void ADC_Init(void)
{
/* resolution : 12bit, software trigger, votage reference : VREF */
ADC_DRV_ConfigConverter(INST_ADCONV1, &adConv1_ConvConfig0); /* for cosine & Vref */
ADC_DRV_ConfigConverter(INST_ADCONV2, &adConv2_ConvConfig0); /* for sine */
/* Enable
SIM_HAL_SetAdcSupplyEnCmd(SIM, 1U); /* Enable internal supply */
SIM_HAL_SetAdcSupplySrc(SIM, 2U); /* VREF ADC Reference monitoring */
/* check register setting */
test_enable = SIM_HAL_GetAdcSupplyEnCmd(SIM); /* I have checked test_enable is 1U */
test_src = SIM_HAL_GetAdcSupplySrc(SIM); /* I have checked test_src is 2U */
/* To verify ADC accuracy */
ADC_DRV_AutoCalibration(INST_ADCONV1); /* for cosine & Vref */
ADC_DRV_AutoCalibration(INST_ADCONV2); /* for sine */
}
void Vref_Measure(void)
{
uint8_t Vref_SumCnt = 0; /* Number of measured channels */
if (Vref_ModeFlg == STOP) /* Is the device in different mode than "stop"? */
{
Vref_ModeFlg = MEASURE; /* Set state of device to the measure mode */
Vref_OutFlg = FALSE; /* Output values aren't available */
Vref_ClrSumV(); /* Clear buffer */
for(Vref_SumCnt=0; Vref_SumCnt<3; Vref_SumCnt++)
{
convertAdcChan(INST_ADCONV1, 0U, VrefChannels[0]); /* Start measurement of next channel */
adc_complete(INST_ADCONV1); /* Wait for conversion complete flag */
Vref_OutV[0] += read_adc_chx(INST_ADCONV1, 0U); /* Save measured value */
}
Vref_OutFlg = TRUE; /* Measured values are available */
Vref_ModeFlg = STOP; /* Set the device to the stop mode */
}
}
void Vref_GetValue(uint16_t *Values)
{
if (Vref_OutFlg == TRUE) /* Is measured value(s) available? */
{
((uint16_t*)Values)[0] = (uint16_t)(Vref_OutV[0] / 3); /* Save measured values to the output buffer */
}
}
