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Need help on SPI interface with M25P20

 
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MemLog
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Need help on SPI interface with M25P20
PostPosted: Mon Oct 09, 2006 12:10 pm     Reply with quote
Hi everyone,
I am trying to setup a communication link between the PIC and M25P20 using SPI. All data returned from read operation is 0.

What's wrong with my code?

Thank you and best regards,
James

Here is a testing code:


Code:

#include <18F442.h>
#device *=16
#include <string.h>
#fuses HS,NOWDT,NOPUT,NOPROTECT, NOBROWNOUT
#use delay(clock=12352000)
#use rs232(baud=19200, xmit=PIN_C6, rcv=PIN_C7, ERRORS)

#define PORTD_CFG 0xE0
#define MEM_CLK   PIN_D0
#define MEM_CS    PIN_D2
#define MEM_WRI   PIN_D3
#define MEM_HOLD  PIN_D4
#define MAX_ADDRESS  262144

int1 ext_fmem_ready(void)
{
   int8 data;
   
   output_low(MEM_CS);
   //RDSR (Read Status Register) has address 5
   spi_write(0x05);
   //Read RDSR, bit0 is Write In Progress (WIP)
   data = spi_read(0);
   output_high(MEM_CS);
   //if WIP is 0, flash memory is ready to write
   return(!bit_test(data, 0));
}

int write_ext_fmem(int32 address, BYTE data)
{
   int wait_timeout = 3;
   
   while(!ext_fmem_ready())
   {
      if(--wait_timeout == 0)
         return 0;
   }
   if( address > (long)MAX_ADDRESS)
      return 0;
     
   output_low(MEM_CS);
   //WREN (Write Enable) address on 6
   spi_write(0x06);
   output_high(MEM_CS);
   
   output_low(MEM_CS);
   //select Page Program
   spi_write(0x02);
   spi_write(address >> 16);
   spi_write(address >> 8);
   spi_write(address);
   //write data
   spi_write(data);
   output_high(MEM_CS);
   return 1;
}
//--------------------------------

int read_ext_fmem(int32 address)
{
   int8 data;
   int wait_timeout = 3;
   
   while(!ext_fmem_ready())
   {
      if(--wait_timeout == 0)
         return 0;
   }
   if(address > MAX_ADDRESS)
      return 0;
     
   output_low(MEM_CS);
   spi_write(0x03);
   spi_write(address >> 16);
   spi_write(address >> 8);
   spi_write(address);
   
   data = spi_read(0);
   output_high(MEM_CS);
   
   return data;
} 

void main ( )
{
   int data;

#use fast_io(D)
   Set_Tris_D(PORTD_CFG);
   
//setup spi
   output_low(MEM_CLK);
   output_high(MEM_CS);   
   setup_spi(SPI_MASTER | SPI_L_TO_H | SPI_CLK_DIV_16 );
   delay_us(20);
   //write to address 10 and read it back
   write_ext_fmem(10, 128);
   data = read_ext_fmem(10); 
}   
PCM programmer



Joined: 06 Sep 2003
Posts: 21708

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PostPosted: Mon Oct 09, 2006 12:22 pm     Reply with quote
Quote:
#define PORTD_CFG 0xE0
#define MEM_CLK PIN_D0
#define MEM_CS PIN_D2
#define MEM_WRI PIN_D3
#define MEM_HOLD PIN_D4

spi_write(address >> 16);
spi_write(address >> 8);
spi_write(address);

What's wrong with my code?


You're using the CCS spi functions, such as spi_write().
These functions only use the hardware SPI pins, which are on Port C.
You need to re-wire the flash memory chip to use those pins.

You have some other things that need be fixed:
1. You need to add the NOLVP fuse.
2. You need a while(1); statement at the end of main().
3. I would get rid of the #fast_io and let CCS handle the TRIS.
Just use output_low(), output_high(), output_float(), etc., and
the compiler will take care of the TRIS.

I didn't try to analyze your code for correctness as a driver.
I just did a quick scan of it.
MELOG
Guest
PostPosted: Mon Oct 09, 2006 12:38 pm     Reply with quote
PortC has reserved for A/D chip. With PortD only, any sample code or it is impossible?

PCM programmer wrote:
Quote:
#define PORTD_CFG 0xE0
#define MEM_CLK PIN_D0
#define MEM_CS PIN_D2
#define MEM_WRI PIN_D3
#define MEM_HOLD PIN_D4

spi_write(address >> 16);
spi_write(address >> 8);
spi_write(address);

What's wrong with my code?


You're using the CCS spi functions, such as spi_write().
These functions only use the hardware SPI pins, which are on Port C.
You need to re-wire the flash memory chip to use those pins.

You have some other things that need be fixed:
1. You need to add the NOLVP fuse.
2. You need a while(1); statement at the end of main().
3. I would get rid of the #fast_io and let CCS handle the TRIS.
Just use output_low(), output_high(), output_float(), etc., and
the compiler will take care of the TRIS.

I didn't try to analyze your code for correctness as a driver.
I just did a quick scan of it.
melog
Guest
PostPosted: Mon Oct 09, 2006 1:09 pm     Reply with quote
PCM programmer,

I found an example code 9346.c under c:\Program Files\PICC\Drivers. Any better ones (using M25P20)?

Thanks.
PCM programmer



Joined: 06 Sep 2003
Posts: 21708

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PostPosted: Mon Oct 09, 2006 1:13 pm     Reply with quote
Look at CCS drivers for memory chips, that use software SPI:

c:\program files\picc\drivers\at45db021.c

c:\program files\picc\drivers\68hc68r2.c
Memlog
Guest
PostPosted: Mon Oct 09, 2006 1:20 pm     Reply with quote
PCM programmer,

Thanks. One of them is perfect maching with my case!
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