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SPI to 25L640 woes :-(

 
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epideath



Joined: 07 Jun 2006
Posts: 47

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SPI to 25L640 woes :-(
PostPosted: Fri Jun 09, 2006 10:29 pm     Reply with quote
(using a 18F4520)

OK having a really tough time trying to communicate to a 25L640 EEPROM. My board electronics all work because I can reload the MCC18 code that I have and it reads and writes to the EEPROM with no problems.

I can't seem to get the PIC to even read one address (zero) from the EEPROM. Crying or Very sad I alos have a write function. but it doesn't seem to work either. I have written a known value to adress zero it is a 1. but after a read it alwyas comes back with zero. Also tried writing a value then read it with my MCC18 program and I can see that it hasn't changed the value. It is the same as that orignally written by the MCC18 program.

I have tried the 25640.c code in the device folder. That doesn't seem to work either. and that doesn't even use the SPI but just drives the I/O directly.

I'm sure that it is something setting wise that i'm over looking. As I'm new to CCS PICC.


Here is the code that I have in CCS PIC-C. Ported from MCC18 that code is below this current code.

I have tried not playing with the SKE and SSPEN. just using the setup_spi. but that doesn't seem to matter one way or the other.

Oh and EditStep.StepType is defined as int8

Hope this makes some sense.

Any pointers or thoughts would be great.
Smile

Thanks

Code:

   SET_TRIS_C(0x10);      //00010000 All output except C4


Code:

      setup_spi(SPI_MASTER|SPI_H_TO_L|SPI_CLK_DIV_4);
   SSPEN = 0;
   SMP = 1;
   CKE = 1;
   SSPEN = 1;




Code:

void Poll_EE(void)
{
   int8 st;
   do
   {
      output_low(PIN_C2);
      spi_write(RDSR);
      st = spi_read();
      output_high(PIN_C2);
   }while(st & 0x01);
}

void LoadStepFromEE(int8 program, int8 step)
{
   int16 address;
   int8 lsb, msb;

   char str[4];

   output_high(PIN_C2);
   address = (int16) program * MAX_STEPS * STEP_SIZE;
   address += (int16)(step-1) * STEP_SIZE;
   lsb = address & 0xFF;
   msb = address >> 8;

   Poll_EE();
   output_low(PIN_C2);
   spi_write(READ_SPI);
   spi_write(0);
   spi_write(0);
   EditStep.StepType = spi_read();
   output_high(PIN_C2);
}




[Here is the MCC18 code that I'm trying to port from.

Code:

void busy_polling (void)
{
   char var;
   do
   {
      PORTCbits.RC2 = 0; //assert chip select
      var = putcSPI(SPI_RDSR); //send read status command
      var = getcSPI(); //read data byte
      PORTCbits.RC2 = 1; //negate chip select
   } while (var & 0x01); //stay in loop until !busy
}

void LoadStepFromEE(char program, char step)
{
   unsigned int address;
   unsigned char address_low, address_high;

   PORTCbits.RC2 = 1;
   //Calculate address high and address low of program/step
   address = (int)(program) * MAX_STEPS * STEP_SIZE;
   address = address + (int)(step-1) * STEP_SIZE;
   address_low = (unsigned char) address & 0xFF;
   address_high = (unsigned char) (address >> 8) & 0xFF;

   OpenSPI(SPI_FOSC_4, MODE_00, SMPEND);
   busy_polling();

   PORTCbits.RC2 = 0;
   putcSPI(SPI_READ);
   putcSPI(address_high);   //Address High
   putcSPI(address_low); //Address Low

   //Read Step Data
   Step.StepType = getcSPI();
   CloseSPI();
   PORTCbits.RC2 = 1;

}
PCM programmer



Joined: 06 Sep 2003
Posts: 21708

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PostPosted: Fri Jun 09, 2006 11:24 pm     Reply with quote
See the following thread, which shows how to use the CCS 25640.C
driver. It's possible that you couldn't make it work because you were
using the wrong pins. The example shows how to use different pins
than the ones defined in the CCS driver file.
http://www.ccsinfo.com/forum/viewtopic.php?t=26212


Also, you should be aware that the following line doesn't generate
an SPI clock:
Code:
st = spi_read();


To generate a clock (from master PIC to slave eeprom), then do this:
Code:
st = spi_read(0);

Note the zero parameter. This is in the manual.
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