Thursday, January 9, 2014

RS-485/422 with Serial Displays

A customer recently posed the question, 'Is there an adapter that would allow me to talk to my GLO-416Y using RS-485?' The answer is, happily, you don't need any kind of adapter! 

Assuming that the project does not require multidrop or long wiring runs, you can connect our displays directly to a differential serial port like RS-485 or RS-422. All you need to do is connect one of the RS-4xx data lines to the display' SER(ial In), and tie the GND lines together. That's it.

Almost it: You have to pick the right data line. For most of our displays, you want the inverted line (TxD-); but on some newer displays such as the GLO, SGX, or BPP-440L that have a serial-polarity jumper (Spol), you will need to pick based on the jumper setting.
  • Spol installed/intact: Use TxD-
  • Spol removed/cut: Use TxD+
For more info on RS-485, the wikipedia entry is pretty good. (illustration above is from their page, courtesy of author Roy Vegard Ovesen). 

No comments:

Post a Comment