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ADS1298 RREG

Lukas K.
Prodigy 100 points
Other Parts Discussed in Thread: ADS1298

Hello,

I am sending the following bytes to the ads1298 via SPI:

0x20 //RREG 0

0 //One register (1-1=0)

0 //ADS1298 sends contents of ID

0 //ADS1298 sends contetns of CONFIG1 ???

Why does the ADS1298 send the contents of CONFIG1, I told it to read only one register.

Is it a bug or a feature?

Kid regards, Lukas

  • 0
    TI__Guru**** 182071 points

    Hi Lukas,

    It would be interesting to know if you continue to send 0x00, would you get back the contents of the other registers as well?  Since you did not send a new command byte before the device sent the contents of CONFIG1, this could be a clue as to why you got the results you did.  If you were to repeat the RREG command with a different starting address, does the same thing happen? 

  • 0 in reply to Tom Hendrick
    Prodigy 100 points

    Hello Tom,

    If I send more zero bytes, the ADS1298 doesn't send more register contents, it just sends two. The same issue appears when reading from another register, e.g. CONFIG1.

    But all in all the ads1298 accepts further commads such as wreg, which were sent after it sent the first register byte.

    If neccessary, I can attatch a vcd dump of the spi communication.

     

  • 0 in reply to Lukas K.
    TI__Guru**** 182071 points

    Hi Lukas,

    I've been over this situation with the design staff and what happens is that the ADS1298 will pre-fetch the register contents of address N+1, so this is a 'feature' of the device.  You ask for one, but can read two if you continue to send 0x00.  No need for scope trace dump.