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Software SPI

 
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Geps



Joined: 05 Jul 2010
Posts: 129

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Software SPI
PostPosted: Wed Jul 06, 2011 6:46 am     Reply with quote
Hi,

I'm trying to communcate with an 96C56 EEPROM using my own driver (rather than CCS' provided one) and need to use the software implementation of SPI.

I've written a short test program and the software seems to be crashing on the spi_write() instruction. Using a logic anaylser the output_high(SPISS) line gets exectued but nothing there after. I'm able to toggle the pins so I know it's not a hardware issue.

Is there something regarding the software versions I should be aware of/am doing wrong?

CCS PCH C Compiler, Version 4.116

Test program:

Code:

#include <18f4520.h>
#fuses INTRC_IO, NOMCLR, NOWDT, NOLVP, NOPUT
                       
#use delay(internal = 8Mhz, clock=32MHz)
#use rs232(baud=115200, xmit=PIN_C6, rcv=PIN_C7, ERRORS)



#define SPI_SS PIN_B4

#use spi(DI=PIN_B2, DO=PIN_B1, CLK=PIN_B3)

void main() {
delay_ms(1000);
while(TRUE){

   
// select slave - this device has high chip select
   output_high(SPI_SS);
   
   spi_write(10);
   delay_ms(1000);
}
}
SH



Joined: 06 Jul 2011
Posts: 3

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PostPosted: Wed Jul 06, 2011 7:16 am     Reply with quote
There is an example for the 93C56:
C:\Program Files (x86)\PICC\drivers\9356spi

Maybe it will help you.
PCM programmer



Joined: 06 Sep 2003
Posts: 21708

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PostPosted: Wed Jul 06, 2011 2:15 pm     Reply with quote
Quote:
#use spi(DI=PIN_B2, DO=PIN_B1, CLK=PIN_B3)

spi_write(10);

The spi_write() function only uses the hardware SPI pins. You must use
the spi_xfer() function with #use spi() for software SPI. spi_xfer() is
intended to be used with #use spi().

The spi_write() and spi_read() functions are for the older setup_spi() method.

Also, depending upon your compiler version, the #use spi() library may
not default to parameters that you expect. It likely defaults to the exact
opposite of what you want. That's what I've found in older compiler
versions. You need to add the following parameters to your #use spi()
declaration:
Code:

MASTER, MSB_FIRST, BITS=8, MODE=0, BAUD=100000

If your SPI mode is different, or if your Baudrate is different, you can
change them to what you need.
Geps



Joined: 05 Jul 2010
Posts: 129

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PostPosted: Thu Jul 07, 2011 9:20 am     Reply with quote
SH, for my application I have to use the software port so the CCS provided driver isn't any use unfortunately.

Thanks PCM - thought it might be something simple!
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