5.6 High Precision Mode

High precision mode increases the accuracy of the data measurement to 16-bit accuracy. In this mode, 16 12-bit conversions are placed into an accumulator that sums up the conversions in the accumulator. Equation 2 calculates the high precision data for each channel.

Each channel has an accumulator. Figure 33 shows the high precision mode conversion dynamics.

The main routine is the following:

#include "ADS7142RegisterMap.h" /* ADS7142_HighPrecisionMode_AutoSequencing_CH0_CH1_Scan.c */ int main(void) { //Initialize the master MCU (0 = 100 kHz SCL, 1 = 400 kHz SCL) TM4C1294Init(0); //Calibrate the offset out of ADS7142 ADS7142Calibrate(); //Let's put the ADS7142 into High Precision Mode with both channels enabled in Single-Ended Configuration //Select the channel input configuration ADS7142SingleRegisterWrite(ADS7142_REG_CHANNEL_INPUT_CFG, ADS7142_VAL_CHANNEL_INPUT_CFG_2_CHANNEL_SINGLE_ENDED); //Confirm the input channel configuration uint32_t channelconfig; ADS7142SingleRegisterRead(ADS7142_REG_CHANNEL_INPUT_CFG, &channelconfig); //Select the operation mode of the device ADS7142SingleRegisterWrite(ADS7142_REG_OPMODE_SEL, ADS7142_VAL_OPMODE_SEL_HIGH_PRECISION_MODE); //Confirm the operation mode selection uint32_t opmodeselconfig; ADS7142SingleRegisterRead(ADS7142_REG_OPMODE_SEL, &opmodeselconfig); //Set the I2C Mode to High Speed (optional) //ADS7142HighSpeedEnable(ADS7142_VAL_OPMODE_I2CMODE_HS_1); //Check the I2C Mode Status uint32_t opmodei2cconfig; ADS7142SingleRegisterRead(ADS7142_REG_OPMODE_I2CMODE_STATUS, &opmodei2cconfig); //Auto Sequence both channels 0 and 1 ADS7142SingleRegisterWrite(ADS7142_REG_AUTO_SEQ_CHEN, ADS7142_VAL_AUTO_SEQ_CHENAUTO_SEQ_CH0_CH1); //Confirm Auto Sequencing is enabled uint32_t autoseqchenconfig; ADS7142SingleRegisterRead(ADS7142_REG_AUTO_SEQ_CHEN, &autoseqchenconfig); //Select the Low Power Oscillator or high speed oscillator ADS7142SingleRegisterWrite(ADS7142_REG_OSC_SEL, ADS7142_VAL_OSC_SEL_HSZ_HSO); //Confirm the oscillator selection uint32_t oscselconfig; ADS7142SingleRegisterRead(ADS7142_REG_OSC_SEL, &oscselconfig); //Set the minimum nCLK value for one conversion to maximize sampling speed ADS7142SingleRegisterWrite(ADS7142_REG_nCLK_SEL, 21); //Confirm the nCLK selection uint32_t nCLKselconfig; ADS7142SingleRegisterRead(ADS7142_REG_nCLK_SEL, &nCLKselconfig); //Enable the accumulator ADS7142SingleRegisterWrite(ADS7142_REG_ACC_EN, ADS7142_VAL_ACC_EN); //Set SEQ_START Bit to start the sampling sequence ADS7142SingleRegisterWrite(ADS7142_REG_START_SEQUENCE, ADS7142_VAL_START_SEQUENCE); //Begin High Precision Mode Scanning Ch0 and Ch1 continuously while(1) { //Sample 16 conversions from each channel while (ADS7142DataRead_count(32) < 0); //Check the Accumulator Status to count the number of conversions complete uint32_t accstatus; ADS7142SingleRegisterRead(ADS7142_REG_ACCUMULATOR_STATUS, &accstatus); //Read the MSB of Ch0 Accumulated Data after 16 accumulations are complete uint32_t accch0MSB; ADS7142SingleRegisterRead(ADS7142_REG_ACC_CH0_MSB, &accch0MSB); //Read the LSB of Ch0 Accumulated Data after 16 accumulations are complete uint32_t accch0LSB; ADS7142SingleRegisterRead(ADS7142_REG_ACC_CH0_LSB, &accch0LSB); //Read the MSB of Ch1 Accumulated Data after 16 accumulations are complete uint32_t accch1MSB; ADS7142SingleRegisterRead(ADS7142_REG_ACC_CH1_MSB, &accch1MSB); //Read the LSB of Ch1 Accumulated Data after 16 accumulations are complete uint32_t accch1LSB; ADS7142SingleRegisterRead(ADS7142_REG_ACC_CH1_LSB, &accch1LSB); //Set the SEQ_START Bit again ADS7142SingleRegisterWrite(ADS7142_REG_START_SEQUENCE, ADS7142_VAL_START_SEQUENCE); } //Return no errors return 0; }

Figure 34 shows the channel configuration and the selection of the opmode and oscillator for this ADS7142 functional mode.

Figure 35 shows the setting of clock cycles required for a conversion, the enabling of accumulators, and the start of the conversion sequence.

Figure 36 shows the number of conversions that fill the accumulator and the results of the high precision accumulation.

Figure 37 shows the accumulated results and restart of the conversion sequence.