Sherwood R-965

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  [Deleted User] Posts: 0

  July 2004

  The checksum is the only unusual thing I see here. It states 8 bits beneath sum of all data from System ID to Data. The idea is you add all the previous bytes and take the lower byte of that sum and stick it at the end.
  
  The device will do the same calulation when the command is received. If the last byte doesn't match it won't respond or send an error code back. It's an error checking thing.
  
  Example for the power on command
  
  $83,$45,$01,$C9
  
  The $83,$45 are a constant for every command. The $01 is the power on command. The $C9 comes from adding $83,$45,$01. The problem comes when the sum is greater than one byte. In that case you drop the higher 8 bits and use just the lower 8 bits.
  
  Hope that helps.

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  [Deleted User] Posts: 0

  July 2004

  Thanks for the feedback. After about two months of fighting with sherwood over this issue, they finally realized that these units havent been shipping with the proper firmware, which left RS-232 disabled. So if anyone else if having these issues, Sherwood says they will have a new relese of firmware soon! :mad:

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  Chip Moody Posts: 727

  July 2004

  Once that firmware is fixed...
  
  If you do something along the lines of
  
  SEND_STRING SomeDev, "($FF+$AA)"
  
  The SEND_STRING call will automatically send the lower byte of the result and ignore the upper.
  
  - Chip

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