Opto-Isolated SPI.

  *
  |  __O    Thomas C. Sefranek  WA1RHP@ARRL.NET
  |_-\<,_   Amateur Radio Operator: WA1RHP
  (*)/ (*)  Bicycle mobile on 145.41 MHz PL 74.4

ARRL Instructor, Technical Specialist, VE Contact.
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> -----Original Message-----
> From: pic microcontroller discussion list
> [mailto:PICLIST@MITVMA.MIT.EDU]On Behalf Of Denny Esterline
> Sent: Sunday, May 09, 2004 3:13 PM
> To: PICLIST@MITVMA.MIT.EDU
> Subject: [EE:] Isolated PIC-PIC communication
>
>
> I'm looking at a project that will have several (4-8) PICs in the circuit.
> They need low bandwidth (~100 bytes/sec) communication between each node
> and the main controller. The problem is they need galvanic
> isolation, there
> could be a couple hundred volts difference between them. Main PIC will
> probably be a 16F877 handling front panel details (character LCD and
> buttons) as well as connection to host PC, nodes will probably be 12F675s
> or 16F676s.
>
> They'll be within a few inches of each other, and there shouldn't be any
> significant 'noise' to overcome. The USART on the main controller is
> already committed and I have to avoid using the interrupts on the nodes (I
> already have several processes happening there) And I'd like to avoid
> crystals/resonators on the nodes if possible. (cost, complexity,
> not needed
> for main task anyway) So I think typical RS232 is out.
>
> I was thinking of perhaps a clocked serial similar to a shift
> register. One
> pin on the central controller for data in, one for data out, and one per
> node for clock.
>
> Doable, but I was hoping for a more elegant solution. Any suggestions?
>
> Thanks,
> -Denny
>
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