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ADS7950: readed ADC result always is 0

Bill Xu
Intellectual 1090 points
Part Number: ADS7950

Dear Product Line Application engineer,

my customer have one question assocated with ADS7950. after power up,

1. my customer write 0x3800  to ADS7950 and hope ADS7950 running in auto-2 mode.

2. then customer send CS and clock signal to read ADC and keep SDI low all the time.

3. customer always read SDO and always get ADC result is 0. 

after go through datasheet, I suggest customer to do below updates.

  1. Power on or reset ADS7950
  2. Send 0x90c0(1001,0000,1100,0000) to ADS7950           --pre-select the last scan channel in auto-2 mode, here configure last channel to ch3 since ADS7950 just has 4-channels. So all channel was scanned.             
  3. Send 0x3C00(0011, 1100, 0000, 0000) to ADS7950.      --Configure Mode Control Register for Auto-2 mode and scan from ch00
  4. Send 0x0000 (0000, 0000, 0000, 0000) to ADS7950      --Configure ADS7950 continued operation in auto-2 mode.       
  5. Keep in mind: you need wait two frame and the third frame is the ADC result. Refer figure 56 of datasheet for details. 

 Could you please show the correct register configure for auto-2 mode?

thanks a ton for supporting!

regards,

Bill