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SPI in PIC by Software

 
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Kristian_Miranda



Joined: 23 Jun 2007
Posts: 1

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SPI in PIC by Software
PostPosted: Sat Jun 23, 2007 11:04 am     Reply with quote
Hello!I'm new in this forum.
I need some example to comunicate two pic's with SPI by software (because the pins of SPI are occupied with I2C). I'm novice in this subject Sad Sad

THANKS THANKS THANKS!!
PCM programmer



Joined: 06 Sep 2003
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PostPosted: Sun Jun 24, 2007 1:16 pm     Reply with quote
The SPI master is easy to do in software, but the slave is a problem.
The problem is that SPI protocol uses a clock edge to sample the data.
You could use an interrupt (INT_EXT) to detect the start of a \CS signal.
Then within the interrupt routine, you could poll the SCLK signal to
determine when the clock edge occurs for each data bit. Then you could
read the SDI pin immediately after that.

An SPI slave could be done in software, but the speed will be limited
because clock edge detection has to be done by polling.
(At least it does in my proposed method).
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