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AD7779 does have a single-shot conversion function.

Question asked by tsfung on Dec 26, 2016
Latest reply on Jan 9, 2017 by musach

I bought a EVAL-AD777xFMCZ rev D from element14.

I config AD7779  as SPI slave mode and connect to TI MSP430 as a master microcontroller.

AD7779->pin 54,55 FORMAT1 and FORMAT0 connect to 3.3V. EVAL-AD777xFMCZ default is SPI mode.

AD7779-> pin33 START connect to 3.3V, 

AD7779-> pin34 SYNC_OUT connect to pin35 SYNC_IN

AD7779-> pin36 RESET connect to MSP430 OUTPUT PORT, ( Power on RESET).

AD7779-> pin18 CS connect to MSP430 OUTPUT port

AD7779-> pin19 SCLK connect to MSP430 Output port

AD7779-> pin20 SDI connect to MSP430 Output port

AD7779-> pin21 SDO connect MSP430 Input Port.

AD7779-> pin 17 CONVST_SAR connect to MSP430 OUTput port.

I set SAR_ADC  following.

AD7779_spi_write(0x11,0x3C); // power up SAR
AD7779_spi_write(0x12,0x2B); //set bit5, SAT_DIAG_MODE-EN
AD7779_spi_write(0x13,0x90); // set bit4, enable SPI slave

toggle pulse 1-0-1 on CONST_SAR pin.

send 0x8000 data from MSP430 SPI to AD7779 and read back the Data.

I got the 12 bit SAR ADC reading.

 

I have problem on 24bit ADC. I cannot get the ADC reading.

I do following

AD7779_spi_write(0x11,0xB4); // power down SAR
AD7779_spi_write(0x12,0x0B); // Restset bit5, SAT_DIAG_MODE-EN =0, SAR discount
AD7779_spi_write(0x13,0x90); //  bit4, enable SPI slave , ADC output to SDO

AD7779_spi_write(0x14,0xC0); //1 DOUT line, status header,Divid by0

AD7779_spi_write(0x12,0x0A); //toggling Bit0 gen sync pulse

AD7779_spi_write(0x12,0x0B); //toggle

 

loop 16 bit frame in two times to get one channel ADC data. (user guide data sheet page 58)

send 0x8000 as data in  during read back ADC output.

Total repeat 8 time to get 8 channel ADC data.

the 8 channel ADC data I got are all same 0x80FF.

 

from user guide data sheet page 51, Table 35 ,Status Header output, bit 7 Alert is high, detect error.

I am not sure. could help me?

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