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Original question:

ADS131A04: On power up, issue reset command, does not return 0xff04 as documented

ADS131A04: power up only return 0xffff in daisy chain

user4123072
Prodigy 40 points
Part Number: ADS131A04

In my solution I extend the numbers of channels to 16 which means there are four devices in the daisy chain.

All devices are configured in Synchronous Slave Mode. The Reset pin is tied to high.  /CS and drdy pins are tied together.

I followed the startup sequence at page 79 and this worked.

and now when I start up my device it only returns 0xff when I send reset command, null command or unclock command.

then I tried to configure the first device. It worked.

how many devices can be in a daisy chain? 

what should I pay more attention to in a daisy chain?

  • 0
    TI__Guru* 97775 points

    Hi,

    First, if you're having problems with the daisy chain it might help to get a schematic for your circuit. However, I just wanted to make sure that you were able to use the startup sequence for all the devices in the chain. In your first comments, it looks like you were able to setup all devices. I would note that this is less like a daisy chain and you are using the /DONE signal from one device to act as the /CS for the next.

    After that you mentioned that the device returns FF when you send a RESET command, NULL command, or UNLOCK command. If you send a reset, you should get the ready response again, you could use the NULL (or multiple NULLs) to see the response which should be FF04. For your system, this could be the expected response, it depends on the following byte.

    However, note that if you do send a RESET command, I would note that the device returns to default state. This means that the device is locked and the ADCs are disabled. It's likely that you would get the FF04 response until the device is unlocked and then send another command or a NULL to see the response.

    If you are having problems, the best way to debug this is to use a logic analyzer to look at all of the control lines /CS, SCLK, DIN, DOUT and the multiple /DONE signals. Looking at the /DONE signal for each device may show if the remaining devices are being enabled at all. Then check the commands going to the device, and review the response of the device in the following word frame. 

    I don't think that doing four ADS131A04 devices in synchronous slave mode in this way would be a problem. The only practical limit to this would be the amount of clock cycles you could do in the data period.

    Joseph Wu

  • 0 in reply to Joseph Wu
    Prodigy 40 points

    sorry for consuming your time.

    it is a problem of soldering. the /done pin of the first device was not soldered firmly.