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ADS1259: To understand response byte coming from device after sending command byte

Husain Asif
Prodigy 10 points
Part Number: ADS1259

Hi,

I am trying to use ADS1259 EVM patch board in the standalone mode.

For writing my own Master I have captured the initialize procedure data coming on SPI ports.

I have observe that for each input command byte is followed by the some unexpected byte on the output port.

The first command byte on DIN input is 11H i.e. SDATAC with 00H on the DOUT port.

The secomd command byte on DIN input is 0AH i.e. STOP with 02H on the DOUT port.

similarly third input byte is 06H with 1DH on the DOUT port.

This behaviour is not given in the datasheet. Is this the response from the device to the input command sent ?

If yes, what is the response for the other commands of the ADS1259 ?

Regards

Husain Asif

  • 0
    TI__Mastermind 44550 points

    Hi Husain,

    Welcome to the TI E2E Forums!

    SPI is capable of supporting full-duplex communication; however, not all SPI devices take advantage of this...For example, when you send single byte commands to the ADS1259, your MCU will read in a byte concurrently while transmitting the command, but the return data is meaningless. If your MCU reads this data into a FIFO, then you'll want read the data from the FIFO to clear it out, but you don't need to do anything with it. I don't think there are any expected return values for any of the single byte SPI commands to the ADS1259. The ADS1259 does not echo received commands.

    For the RREG command the MCU should send the command bytes and ignore the first two return bytes. Then the following return bytes will contain the register data.

    For reading data, you can either send 0x00 (i.e. NOP) bytes after /DRDY goes low in RDATAC mode and the ADC will shift out data immediately; OR you can issue the RDATA command while in SDATAC mode (ignoring the first return result) and then proceed to clocking out the data with additional NOP bytes.

     

    NOTE: Most commands should be issued in while in SDATAC mode, otherwise the ADC just clocks out data directly.