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Data storage by SPI on 18F452s

 
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AdamkT1



Joined: 21 Apr 2007
Posts: 44

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Data storage by SPI on 18F452s
PostPosted: Mon May 21, 2007 8:25 pm     Reply with quote

Friends,
I am trying to save data in the EPROM memory of 18f452. The code is very simple which I copied from CCS examples.
One 18F452 is acting as a master and the other 18F452 is emulating 9356 EPROM.
I am trying to write to an address and then read from the same address.
Later, I would put the data on a port for display/debug purpose.
The problem, I am having in Proteus is the following message.

[PIC18] PC=0X0000 $MCLR$ is Low. Processor is in Reset U2(SLAVE)
[PIC18] PC=0X0000 $MCLR$ is Low. Processor is in Reset U2(MASTER)
Does it mean that I have to power the MCLR pin.

Both the codes, the master/slave is pasted below.

'===============U2(SLAVE)====================
#include <18F452.h>
#fuses HS,NOWDT,NOPROTECT,NOLVP
#use delay(clock=20000000)
#use rs232(baud=9600, xmit=PIN_C1, rcv=PIN_C0)

int8 memory[80], data, instr, address;

/*
void write_data(void)
PURPOSE: Reads data from SPI and writes it to memory
PARAMS: none
RETURNS: None
*/
void write_data(void)
{
while(!spi_data_is_in());

data = spi_read();

if(address >= 0 || address <= 80)
{
memory[address] = data;
}
}

/*
BYTE read_data(void)
PURPOSE: To read the memory
PARAMS: none
RETURNS: Data stored in memory
*/
BYTE read_data(void)
{
return (memory[address]);
}

/*
void main(void)
PURPOSE: Peripheral Initialization
*/
void main(void)
{
setup_spi(spi_slave | spi_h_to_l | spi_ss_disabled);

while(true)
{
while(!spi_data_is_in());
instr = spi_read();

while(!spi_data_is_in());
address = spi_read();

if (instr == 0x18)
{
instr = spi_read(memory[address]);
}
else if(instr == 0xa)
{
write_data();
}
}
}


'==============U1(Master)==========================

#include <18F452.h>
#fuses HS,NOWDT,NOPROTECT,NOLVP
#use delay(clock=20000000)
#use rs232(baud=9600, xmit=PIN_A0, rcv=PIN_A1)

#include <9356spi.c>
BYTE PORT_A;

void main()
{
int8 value;
EEPROM_ADDRESS address;

address=1;

init_ext_eeprom();

do
{
WRITE_EXT_EEPROM( address, 35 );
value=READ_EXT_EEPROM( address );
PORT_A=value;
delay_ms(500);
PORT_A=0;

} while (TRUE);
}
'======================Code End==================
Thanks.
ckielstra



Joined: 18 Mar 2004
Posts: 3680
Location: The Netherlands

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PostPosted: Tue May 22, 2007 1:01 am     Reply with quote

When posting code please use the 'code' buttons to preserve formatting.

Quote:
The problem, I am having in Proteus is the following message.

[PIC18] PC=0X0000 $MCLR$ is Low. Processor is in Reset U2(SLAVE)
[PIC18] PC=0X0000 $MCLR$ is Low. Processor is in Reset U2(MASTER)
Does it mean that I have to power the MCLR pin.
Use the search function of this forum and type 'proteus MCLR', select the 'search for all terms'option. This will give you 5 hits. Read http://www.ccsinfo.com/forum/viewtopic.php?t=28419&highlight=proteus+mclr

Short: Yes, you have to connect MCLR to the positive power supply.

Your check for memory buffer overflow is incorrect.
Code:
if(address >= 0 || address <= 80)
Change this to
Code:
if(address >= 0 || address < 80)
AdamkT1



Joined: 21 Apr 2007
Posts: 44

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SPI between two 18F452
PostPosted: Wed May 23, 2007 9:16 am     Reply with quote

Hi friends,

Still having troubles with SPI between two 18F452s. The slave is emulating 9356 EEPROM.
Below is the modified code. I hope somebody would help me solve this problem.
The error(s):
1) In Proteus, the error is : [PIC18 MSSP] PC=0X0052 MSSP slave mode with no SS pin control and CKE==1 is ambiguous U2(SLAVE)
2) Data does not show up on PORTB as I intend to. In fact nothing happen to the PORT.

Code:

=========SLAVE==========

#include <18F452.h>
#fuses HS,NOWDT,NOPROTECT,NOLVP
#use delay(clock=20000000)
#use rs232(baud=9600, xmit=PIN_C6, rcv=PIN_C7)

int8 memory[80], data, instr, address;

/*
void write_data(void)
PURPOSE: Reads data from SPI and writes it to memory
PARAMS: none
RETURNS: None
*/
void write_data(void)
{
   while(!spi_data_is_in());
   
   data = spi_read();
   
   if(address >= 0 && address <= 80) // AND operator seems logical here.(atleast to me)
   {
      memory[address] = data;
   }
}

/*
BYTE read_data(void)
PURPOSE: To read the memory
PARAMS: none
RETURNS: Data stored in memory
*/
BYTE read_data(void)
{
    return (memory[address]);
}

/*
void main(void)
PURPOSE: Peripheral Initialization
*/
void main(void)
{
   setup_spi(spi_slave | spi_h_to_l | spi_ss_disabled);

   while(true)
   {
      while(!spi_data_is_in());
      instr = spi_read();
     
      while(!spi_data_is_in());
      address = spi_read();

      if (instr == 0x18)
      {
         instr = spi_read(memory[address]);
      }
      else if(instr == 0xa)
      {
         write_data();
      }
   }
}

=====================Master================

#include <18F452.h>
#fuses HS,NOWDT,NOPROTECT,NOLVP
#use delay(clock=20000000)
#use rs232(baud=9600, xmit=PIN_C6, rcv=PIN_C7)

#include <9356spi.c>


void main()
{
   byte value;
   EEPROM_ADDRESS address;
   SET_TRIS_B(0); // make PORTB all outputs.
   PORTB=0;
   address=1;
   value=35;
   init_ext_eeprom();

   do
   {   
         PORTB=0;
         delay_ms(500);
         WRITE_EXT_EEPROM( address, value );
         PORTB=READ_EXT_EEPROM(address);
         delay_ms(500);
   } while (TRUE);
}
==========9365SPI.C=========

#define EEPROM_SELECT PIN_B0
#define EEPROM_DI     PIN_C5
#define EEPROM_DO     PIN_C4
#define EEPROM_CLK    PIN_C3

#define EEPROM_ADDRESS BYTE
#define EEPROM_SIZE    256


void init_ext_eeprom()
{
   short int i;

   output_low(EEPROM_DI);
   output_low(EEPROM_CLK);
   output_low(EEPROM_SELECT);
   i=input(EEPROM_DO);

   setup_spi(SPI_MASTER | SPI_H_TO_L | SPI_CLK_DIV_16);

   output_high(EEPROM_SELECT);
   spi_write(0x9);
   spi_write(0x80);
   output_low(EEPROM_SELECT);
}


void write_ext_eeprom(EEPROM_ADDRESS address, BYTE data)
{

   output_high(EEPROM_SELECT);
   spi_write(0xa);
   spi_write(address);
   spi_write(data);
   output_low(EEPROM_SELECT);
   delay_ms(11);
}


BYTE read_ext_eeprom(EEPROM_ADDRESS address)
{
   BYTE data;

   output_high(EEPROM_SELECT);
   spi_write(0x18);
   spi_write(address);
   data=spi_read(0);
   output_low(EEPROM_SELECT);

   return(data);
}
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