Hi,
I am trying calibration of ADC in S32K146. After integrating calibration of ADC, I am not getting proper readings (much worse than without calibration). Please point out any mistakes in calibration or initialization. Thanks in advance.
I am using the following code:
void ADC0_calibration(void)
{
PCC->PCCn[PCC_ADC0_INDEX] &=~ PCC_PCCn_CGC_MASK; // Disable clock to change PCS
PCC->PCCn[PCC_ADC0_INDEX] |= PCC_PCCn_PCS(6); // PCS=6: Select SPLLDIV2_CLK 40 MHz
PCC->PCCn[PCC_ADC0_INDEX] |= PCC_PCCn_CGC_MASK; // Enable bus clock in ADC
ADC0->CFG1 = ADC_CFG1_ADIV(1) // ADIV=1: Prescaler=2; 40/2= 20MHz
|ADC_CFG1_MODE(1) // MODE=1: 12-bit conversion
|ADC_CFG1_ADICLK(0); // Same clk
ADC0->CFG2 = 0x00000000C; // SMPLTS=12: sample time is 13 ADC clks
ADC0->SC2 = 0x00000000; // ADTRG=0: SW trigger
// ACFE,ACFGT,ACREN=0: Compare func disabled
// DMAEN=0: DMA disabled
// REFSEL=0: Voltage reference pins= VREFH, VREEFL
ADC0->SC3 = ADC_SC3_CAL(1)
|ADC_SC3_AVGE(1)
|ADC_SC3_AVGS(3);
while(((ADC0->SC1[0] & ADC_SC1_COCO_MASK)>>ADC_SC1_COCO_SHIFT)==0); //wait for COCO bit to set
}
After calibration, I am changing the clock frequency in this function:
void ADC0_init(void)
{
PCC->PCCn[PCC_ADC0_INDEX] &=~ PCC_PCCn_CGC_MASK; // Disable clock to change PCS
PCC->PCCn[PCC_ADC0_INDEX] |= PCC_PCCn_PCS(6); // PCS=6: Select SPLLDIV2_CLK 40 MHz
PCC->PCCn[PCC_ADC0_INDEX] |= PCC_PCCn_CGC_MASK; // Enable bus clock in ADC
ADC0->SC1[0] =0x00001F; /* ADCH=1F: Module is disabled for conversions*/
/* AIEN=0: Interrupts are disabled */
ADC0->CFG1 = 0x000000004; /* ADICLK=0: inputCLK=SPLLDIV2_CLK= 40 MHz
/* ADIV=0: Prescaler=1 */
/* MODE=1: 12-bit conversion */
ADC0->CFG2 = 0x00000000C; /* SMPLTS=12: sample time is 13 ADC clks */
ADC0->SC2 = 0x00000000; /* ADTRG=0: SW trigger */
/* ACFE,ACFGT,ACREN=0: Compare func disabled */
/* DMAEN=0: DMA disabled */
/* REFSEL=0: Voltage reference pins= VREFH, VREEFL */
ADC0->SC3 = 0x00000000; /* CAL=0: Do not start calibration sequence */
/* ADCO=0: One conversion performed */
/* AVGE,AVGS=0: HW average function disabled */
}
The functions are called in main function in the following sequence:
NormalRUNmode_80MHz() ; // Init clocks: 80 MHz sysclk & core, 40 MHz bus, 20 MHz flash
PORT_init() ; // Configure ports
ADC0_calibration(); //CALIBRATION
ADC0_init() ; // Init ADC resolution 12 bit
for(;;)
{
convertAdc0Chan(14); /* Convert Channel ADC0_SE14 */
while(adc0_complete()==0){} /* Wait for conversion complete flag */
x = read_adc0_chx();
delay();
}
