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ADS1100: Configuration register returning weird values?

PieterT
Intellectual 640 points
Part Number: ADS1100


Hey everyone,

I've got an ADS1100 hooked up with part number ADS1100A3.

I can write and read to the device, although when writing to the device I send it the following:

ST (Bit 7)  = 0

(Bit 6)  = 0

(Bit 5)  = 0

SC (Bit 4) = 0

DR (Bit 3) = 0

DR (Bit 2) = 0

PGA (Bit 1) = 0

PGA (Bit 0) = 0

So I write to the device with address as 0x48 and data as 0x00.

After doing this I read the data from the device( I read 3 bytes with the third being the configuration register) and the device returns 

0x80 or 10000000

This seems to be the general case for anything I write to the configuration register. Whichever value I write, the register returns a different value. 

For instance writing 0x1F to the device returns 0x80 aswell, weirdly changing the address to 0x00 and the data 0x06 does create a general reset call to the device as it become unresponsive for a brief period.

The I2C has a 10k pullup on each line is operating in fast mode with 400 kHz.

Am I just misunderstanding the contents of the configuration register or is something wrong?

Thanks in advance for any help!

  • 0
    Intellectual 640 points

    Confirmed with a logic analyzer, definitely getting the configuration register returning different values than were sent.

  • 0 in reply to PieterT
    TI__Guru* 98145 points

    Pieter,


    For your first comments, reading back 0x80 is the expected response. If you've written 0x00 to the configuration register, the device is in continuous conversion mode. In that mode, the ST/BSY bit always reads back 1, which is the most significant bit. This is mentioned on page 10 of the datasheet in the latter half of the description of the ST/BSY bit.

    For the other comments, I'd need to see the write to the configuration register. If you still have the logic analyzer hooked up, can you please post a pick of the communication?


    Joseph Wu

  • 0 in reply to Joseph Wu
    TI__Guru* 98145 points

    Pieter,

    I haven't heard from you in a little while so I just wanted to check and see if you were able to solve the communication problem. In my last post, I suggested posting a logic analyzer or scope shot of the I2C communication.

    I'll close this post for now, but if you continue to have problems, post back with some shots to review, and we can continue to look at this issue.

    Joseph Wu