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ADS1248 Write to Register Problem

Yuriy Lev
Prodigy 30 points
Other Parts Discussed in Thread: ADS1248

Hi,

I'm using ADS1248. I have a problem to write in to the registers,

I am success  to read from any register , but i can not write (change) him.

My config 

SPI : CPOL=0, CPHA = 1 ....

Start and reset is high.

 but if i write 40 00 03 , i again receive 01 and not 03 ?

And why when i writing to register , i receive any bit from MISO channel (see picture)

  • 0
    TI__Guru 55466 points

    Hi Yuriy,

    The CPOL and CPHA settings appear to be correct; however, it appears that you are running SCLK at a frequency higher than 2.048 MHz.  The ADS1248 can accept a SCLK minimum period of 488ns or a maximum SCLK frequency of ~2.048 MHz.  If you reduce the SCLK frequency; are you able to read/write the register contents?

    Best Regards,

    Luis

  • 0 in reply to Luis Chioye
    Prodigy 30 points

    Hi Luis,

    Thanks  for your reply.

    You're right,  I used  the frequency 4MHz , now i got to 1MHz and i am still receive same results.

    I able to read , i get default values in beginning but not make to change him .

    Best Regards,  

  • 0 in reply to Yuriy Lev
    TI__Guru** 113765 points

    Hi Yuriy,

    The ADS1248 powers up in RDATAC mode where the data is automatically placed in the output buffer after each conversion cycle.  When reading/writing registers it is always a good idea to place the device in SDATAC mode which stops the automatic placement of the data in the output buffer.  Following the completion of the SDATAC command you need to wait for the current conversion to complete before the command takes affect.  You should then be able to read and write registers with expected results.

    If you still have problems, could you post the screen shots as you did in the first post so we can re-evaluate the data.

    Best regards,

    Bob B

  • 0 in reply to Bob Benjamin
    Prodigy 30 points

    Hi Bob,

    Tanks for your reply, I had solved the problem,

    I just need to write to registers once after RESET and START is high, before DRDY start running .

    Best Regards,