• State TI Thinks Resolved
  • Locked Locked
  • Replies 3 replies
  • Answers 2 answers
  • Subscribers 46 subscribers
  • Views 140 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

ADS1247: ADS1247

George Sarkees
Prodigy 10 points
Part Number: ADS1247

After a Sync Command is sent (04h) with a PGA setting of 160 SPS, the spec indicates that data will  be ready 6.240mS after. 

If I send RDATA (12h) after 6.240mS from the sync, will I have to wait another 6.240 mS to get an accurate reading? 

So order is

sync (0x04)

wait 6.240 (actually waiting 9 ms)

RDATA (0x12)

can I expect valid data at this point or would I have to wait again?

Thank you,

George

  • 0
    TI__Mastermind 35171 points

    Hi George,

    No, if you issue a SYNC command, wait the time specified in Table 14, then issue an RDATA command, you will get data from the selected input channels. We would recommend using the DRDY signal to determine when data is ready, and not simply use a counter, as the latter action can sometimes lead to reading data incorrectly or at the wrong time.

    Is there something in the datasheet that suggests you would need to wait more time to get data?

    -Bryan

  • 0 in reply to Bryan Lizon86
    Prodigy 10 points

    Hi Bryan,

    Thank you for the response. It was not clear if RDATA required waiting or not. For the application, we need to take a reading every 9 mS.  so we are not using DRDY.  We set sample rate to 160 SPS thinking it would be safe reading every 9 mS. What is the tolerance of the conversion time once SYNC is sent? 

    Thank you,

    George

  • 0 in reply to George Sarkees
    TI__Mastermind 35171 points

    Hi George,

    The commands, etc., are subject to the timing requirements specified in Table 7.6 in the datasheet. As long as these requirements are met, you should be okay.

    The tolerance depends on the tolerance of the oscillator frequency. The internal oscillator has a tolerance of +/-5%, so this directly relates to the tolerance you would see on the conversion latency. But this will not change the latency too much, especially if you have several milliseconds to spare. Moreover, since you are not continuously converting you should not have to worry too much about the timer getting out of sync with the conversion data. I assume you will start your internal counter after the last bit of the SYNC command is clocked in, and then issue the RDATA command after ~6.25ms + tolerance.

    -Bryan