c - Pic to Pic communcation through SPI -

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i trying make pic1 master , pic2 slave through spi communication. want send command pic1 (master) pic2 (slave), have something. want establish spi communication pic2 (slave) digital potentiometer (mcp4241) through spi communication well. work ?

to illustrate :

pic1 sends 'a' ---- > pic2 reads

pic2 ---- > establishes connection digital pot(mcp4241)

pic2 ---- > sends data digital pot

so there spi communications between pic1 , pic2, pic2 , digital pot, don't know if going work since need use same pins. 2 pics, using pic16f690.

i hope question clear , please if won't work how should fix it?

thanks!

first of all, easy life, i'd recommend using pic 2 spi ports pic2.

however, if sure want use 1 spi port master , slave thing keep in mind don't want both pics try drive serial line @ same time. may have write tris registers make port tristate go high-z disabling spi peripheral.

  • if put series resistors in things less bad if e.g. pic1 tries drive sclk high while pic2 trying drive low current flowing pic1 pic2 limited

  • you use gpio allow pic2 tell pic1 when busy. need have clear idea of flow of execution between 2 devices don't caught race conditions etc

  • for example have flow of

  • pic1 sends 'write pot please' command pic2
  • pic1 knows wait busy signal
  • pic2 asserts busy signal
  • pic1 sees busy signal , knows wait clear before starting spi transaction
  • pic2 spi transaction pot
  • pic2 clears busy signal
  • pic1 sees busy signal has cleared , knows ok spi transactions
  • pic2 not try spi transaction until gets 'write pot please'

there loads of ways implement this. important thing know flow going before start implementation


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