MSPM0G1506: DAC: CALCTL CALSEL bit

Hi Zane,

Enabling the CALON bit allows the user to calibrate any offset errors to achieve the best performance of the DAC. 

CALSEL bit let the user chooses whether to use the factory trimmed value which is one time adjustment during final test or using the Self Calibration during customer user case to Calibrate the best trim value. It is default to Factory trim but using the Self Calibration Trim will have better results.

In order to achieve the best results, we want to enable CALON bit to initiate the offset error calibration and enable CALSEL bit to self calibration trim to calibrate to the optimal trim to compensate the offset errors. Therefore in the Driverlib we setting the DAC12_CALCTL_CALSEL_SELFCALIBRATIONTRIM.

Regards,

Bill

Hi Bill,

I do some tests on M0G1507-LP, and import dac12_fixed_voltage_vref_internal_LP_MSPM0G3507_nortos_ticlang demo, use multimeter to measure PA15 and GND.

I use below code to test ADC  Calibration function:

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#include "ti_msp_dl_config.h"

/*
 * DAC12 Reference Voltage in mV
 *  Adjust this value according to DAC12 reference settings in SysConfig
 *    Or, in registers CTL1.REFSN and CTL1.REFSP
 */
#define DAC12_REF_VOLTAGE_mV (2500)
/*
 * DAC12 static output voltage in mV
 *  Adjust output as needed and check in DAC_OUT pin
 */
#define DAC12_OUTPUT_VOLTAGE_mV (100)

int main(void)
{
    uint32_t DAC_value;
    uint32_t DAC_CALDATA;

    uint32_t realdata;



    SYSCFG_DL_init();

    DL_DAC12_performSelfCalibrationBlocking(DAC0);

    DAC_CALDATA = DL_DAC12_getCalibrationData(DAC0);



    /* Set output voltage:
     *  DAC value (12-bits) = DesiredOutputVoltage x 4095
     *                          -----------------------
     */
    DAC_value = (DAC12_OUTPUT_VOLTAGE_mV * 4095) / DAC12_REF_VOLTAGE_mV;

    realdata = DAC_value + DAC_CALDATA;

    DL_DAC12_output12(DAC0, realdata);
    DL_DAC12_enable(DAC0);

    while (1) {
        __WFI();
    }
}

When #define DAC12_OUTPUT_VOLTAGE_mV (1000)

Don’t perform Calibration: PA15 voltage is 0.991V

After perform Calibration and add CALDATA: PA15 voltage is 1.030V

When #define DAC12_OUTPUT_VOLTAGE_mV (100)

Don’t perform Calibration: PA15 voltage is 99.1mV

After perform Calibration and add CALDATA: PA15 voltage is 138.4mV

From the test results: After DAC Calibration, DAC output precision get worse.

Hi Zane,

I made some adjustment on the code you provided above.

#include "ti_msp_dl_config.h"

/*
 * DAC12 Reference Voltage in mV
 *  Adjust this value according to DAC12 reference settings in SysConfig
 *    Or, in registers CTL1.REFSN and CTL1.REFSP
 */
#define DAC12_REF_VOLTAGE_mV (2500)
/*
 * DAC12 static output voltage in mV
 *  Adjust output as needed and check in DAC_OUT pin
 */
#define DAC12_OUTPUT_VOLTAGE_mV (2000)



int main(void)
{
    uint32_t DAC_value;
    uint32_t DAC_CALDATA;
    uint32_t realdata;

    SYSCFG_DL_init();
    // DL_DAC12_performSelfCalibrationBlocking(DAC0);

    // DAC_CALDATA = DL_DAC12_getCalibrationData(DAC0);
    /* Set output voltage:
     *  DAC value (12-bits) = DesiredOutputVoltage x 4095
     *                          -----------------------
     *                              ReferenceVoltage
     */
    DAC_value = (DAC12_OUTPUT_VOLTAGE_mV * 4095) / DAC12_REF_VOLTAGE_mV;
    DL_DAC12_enable(DAC0);
    
    DL_DAC12_performSelfCalibrationBlocking(DAC0);
    DAC_CALDATA = DL_DAC12_getCalibrationData(DAC0);
    realdata = DAC_value - DAC_CALDATA;
    DL_DAC12_output12(DAC0, realdata);
    // DL_DAC12_output12(DAC0, DAC_value);

    while (1) {
        __WFI();
    }
}

Without the calibration and with voltage Output 1000 mV PA15  measured: 1.012 V

With calibration: PA15 Voltage is 1.008 V

Without the calibration and with voltage Output 2000 mV PA15 measured: 2.010V

With calibration: PA15 Voltage is: 2.006 V

I hope this helps.

Regards,

Bill