5.4 Autonomous Mode With Start Burst Data

In autonomous mode with start burst data functional mode, the ADS7142 can be configured to start filling the data buffer when starting the conversion sequence. After the data buffer is filled, conversion stops. Figure 25 shows how this functional mode handles conversions.

The main routine is the following:

#include "ADS7142RegisterMap.h" /* *ADS7142_AutonomousMode_StartBurst_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 Start Burst mode ADS7142SingleRegisterWrite(ADS7142_REG_DATA_BUFFER_OPMODE, ADS7142_VAL_DATA_BUFFER_STARTSTOP_CNTRL_STARTBURST); //Set the SEQ_START Bit to begin the sampling sequence ADS7142SingleRegisterWrite(ADS7142_REG_START_SEQUENCE, ADS7142_VAL_START_SEQUENCE); //Begin Autonomous Mode StartBurst operation and scan both channels 0 and 1 while (1) { uint32_t databufferstatus; uint32_t sequencestatus; //Fill and read the data buffer do { while (ADS7142DataRead_count(16) < 0); } //Ensure that the data buffer is not filled and the sequence is not aborted while ((ADS7142SingleRegisterRead(ADS7142_REG_DATA_BUFFER_STATUS, &databufferstatus) < 0x10) \ && (ADS7142SingleRegisterRead(ADS7142_REG_SEQUENCE_STATUS, &sequencestatus) == 0x02)); //Restart the sequence ADS7142SingleRegisterWrite(ADS7142_REG_START_SEQUENCE, ADS7142_VAL_START_SEQUENCE); } //Return no errors return 0; }

Figure 26 shows the channel configuration and selection of the opmode for this autonomous mode.

Figure 27 shows the contents of the data buffer when filled.

After the data buffer contents are clocked out, there are no remaining conversions within the buffer. The conversion sequence must be restarted for the buffer to be filled again. Figure 28 shows this process.