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ADS8329: SPI Data Transfer

Christopher Williams79
Prodigy 140 points
Part Number: ADS8329


Does the ADS8329 automatically transfer the last conversion result out on the SDO line when the CS goes low or does a read command need to be sent first? The diagrams are raising more questions than they're answering.

In Figure 5, it looks like a READ command is sent on the SDI line at the same time that data is being output on the SDO line. 

In Figure's 60 through 62, it seems like data is being shifted out even before the READ command. I have all sorts of questions about Figure 61, but I'll leave those alone for now.

Really I just want to know what I need to do to read data out of the converter.

  • 0
    TI__Intellectual 1205 points

    From P. 30 of the ADS8329 datasheet, a read command does not need to be sent.  After the falling edge of CS, the MSB is clocked out on the next rising edge of SCLK, which you can latch into your controller on the falling edge.

    Figure 5 is illustrating data transfer (a 16-bit conversion result) out of the ADC while 16-bits of data are written to the ADC's registers; 4 bits to the Command Register, then 12 bits to the Configuration Register.  (This is not a READ command.)

    Figures 60-62 are showing multiple converters in cascade mode.  This allows using multiple converters with a single SPI interface, and also supports simultaneous sampling.  In this mode, each converter is clocking out what it receives on the SDI, then adds its own conversion result to the end.

    I hope this helps!