5.3 Autonomous Mode With Post-Alert

In autonomous mode with post alert data, the ADS7142 captures the 16 conversion results after the alert is activated. Figure 20 shows the filling of the data buffer in autonomous mode with post alert data.

The main routine for this functional mode is the following:

#include "ADS7142RegisterMap.h" /* ADS7142_AutonomousMode_PostAlert_AutoSequencing_CH0_CH1_Scan.c */ int main(void) { //Initialize the master MCU (0 = 100 kHz SCL, 1 = 400 kHz SCL) TM4C1294Init(0); //Calibrate out the offset from the ADS7142 ADS7142Calibrate(); //Let's put the ADS7142 into Autonomous 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_AUTONOMOUS_MONITORING_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); //Select both channels for AUTO Sequencing 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 or High Speed Oscillator ADS7142SingleRegisterWrite(ADS7142_REG_OSC_SEL, ADS7142_VAL_OSC_SEL_HSZ_HSO); //Confirm the oscillator selection uint32_t oscconfig; ADS7142SingleRegisterRead(ADS7142_REG_OSC_SEL, &oscconfig); //Set the minimum nCLK value for one conversion to maximize sampling speed ADS7142SingleRegisterWrite(ADS7142_REG_nCLK_SEL, 21); //Confirm the nCLK selection uint32_t nCLKconfig; ADS7142SingleRegisterRead(ADS7142_REG_nCLK_SEL, &nCLKconfig); //Select the Data Buffer output data Configuration ADS7142SingleRegisterWrite(ADS7142_REG_DOUT_FORMAT_CFG, ADS7142_VAL_DOUT_FORMAT_CFG_DOUT_FORMAT2); //Select the Data Buffer opmode for Post-Alert mode ADS7142SingleRegisterWrite(ADS7142_REG_DATA_BUFFER_OPMODE, ADS7142_VAL_DATA_BUFFER_STARTSTOP_CNTRL_POSTALERT); //Configure CH0 High Threshold MSB ADS7142SingleRegisterWrite(ADS7142_REG_DWC_HTH_CH0_MSB, 0x90); //Configure CH0 High Threshold LSB ADS7142SingleRegisterWrite(ADS7142_REG_DWC_HTH_CH0_LSB, 0x00); //Configure CH0 Low Threshold MSB ADS7142SingleRegisterWrite(ADS7142_REG_DWC_LTH_CH0_MSB, 0x00); //Configure CH0 Low Threshold LSB ADS7142SingleRegisterWrite(ADS7142_REG_DWC_LTH_CH0_LSB, 0x00); //Set the Hysteresis for CH0 ADS7142SingleRegisterWrite(ADS7142_REG_DWC_HYS_CH0, 0x00); //Configure CH1 High Threshold MSB ADS7142SingleRegisterWrite(ADS7142_REG_DWC_HTH_CH1_MSB, 0xE0); //Configure CH1 High Threshold LSB ADS7142SingleRegisterWrite(ADS7142_REG_DWC_HTH_CH1_LSB, 0x00); //Configure CH1 Low Threshold MSB ADS7142SingleRegisterWrite(ADS7142_REG_DWC_LTH_CH1_MSB, 0x00); //Configure CH1 Low Threshold LSB ADS7142SingleRegisterWrite(ADS7142_REG_DWC_LTH_CH1_LSB, 0x00); //Set the Hysteresis for CH1 ADS7142SingleRegisterWrite(ADS7142_REG_DWC_HYS_CH1, 0x00); //Enable Alerts ADS7142SingleRegisterWrite(ADS7142_REG_ALERT_CHEN, ADS7142_VAL_ALERT_EN_CH0_CH1); //Enable the digital window comparator block ADS7142SingleRegisterWrite(ADS7142_REG_ALERT_DWC_EN, ADS7142_VAL_ALERT_DWC_BLOCK_ENABLE); //Set the SEQ_START Bit to begin the sampling sequence ADS7142SingleRegisterWrite(ADS7142_REG_START_SEQUENCE, ADS7142_VAL_START_SEQUENCE); //Begin Autonomous Mode Post-Alert operation and Scan both channels 0 and 1 while (1) { //Start Scanning CH0 and CH1 //If Alert is set, device stops conversions and filling the data buffer //Read the latched flags of the Digital Window Comparator while (ADS7142DataRead_autonomous() < 0); //Reset the alert flags ADS7142SingleRegisterWrite(ADS7142_REG_ALERT_HIGH_FLAGS, 0x03); ADS7142SingleRegisterWrite(ADS7142_REG_ALERT_LOW_FLAGS, 0x03); //Read the Data Buffer Status uint32_t databufferstatus; ADS7142SingleRegisterRead(ADS7142_REG_DATA_BUFFER_STATUS, &databufferstatus); //Read the Data Buffer while (ADS7142DataRead_count(16) < 0); //Restart the sequence ADS7142SingleRegisterWrite(ADS7142_REG_START_SEQUENCE, ADS7142_VAL_START_SEQUENCE); } //Return no errors return 0; }

Figure 21 shows the channel configuration and selection of the opmode for this ADS7142 functional mode.

Figure 22 shows the conversion clock, data buffer configuration, output data format configuration, setting of thresholds for channel 0, and setting of hysteresis for channel 0.

Figure 23 shows the setting of thresholds and hysteresis for channel 1, the enabling of alerts, and the start of the conversion sequence.

Figure 24 shows the data results for the alert flag resets, reading of the data buffer status, and clocking out the data inside the data buffer after the alert is triggered.