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TMP1826: Getting 256 unique IDs based on IO and resistor value

Roy van Lierop
Prodigy 70 points
Part Number: TMP1826

Hello engineers,

Could you verify the following:

If one would like to get 256 unique ID's based on hardware then the following steps need to be followed:

  1. Read the scratchpad
  2. Modify the scratchpad such that FLEX_ADDR_MODE='01b'
  3. Calculate the CRC of the modified scratchpad
  4. Write the modified scratchpad to the device
  5. Read the scratchpad again and save SHORT_ADDRESS[3:0]
  6. Modify the scratchpad such that FLEX_ADDR_MODE='10b'
  7. Calculate the CRC of the modified scratchpad
  8. Write the modified scratchpad to the device
  9. ? 'place the device in shut down mode' ?
  10. Wait 2.8ms
  11. Read the scratchpad again and save SHORT_ADDRESS[3:0]

Step 9 is what I'm struggling with, what is shut down mode?

With regards,
Roy

  • 0
    TI__Guru* 91186 points

    Roy - 

    Thanks for the post. The part is in shutdown mode when bus is idle and no conversion is in process. So in your case, you just need to have a delay, so the part goes to sleep, which you already do have by respecting the 2.8mSec delay for tRESDET. 

  • +1
    TI__Guru**** 244380 points

    Hi Roy

    Let me clarify the short address mode. Combined IO and resistor value allow for up to 64 short-address without the complex steps. Any further addition of address requires the 64 device chain to have a base short address first before loading the combined IO and resistor decode.

    As Josh mentioned, the default factory power up mode for the device is one-shot. Until the one-shot command mode is issued the device shall continue to be in shutdown mode.

    Regards

    Amit Ashara

  • 0 in reply to Josh Wyatt
    Prodigy 70 points

    Great, thanks for that information. The datasheet wasn't very specific about this mode.