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J Hopkins
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| Switching from hardware spi to software spi |
 Posted: Sun May 10, 2009 2:28 pm |
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I am using a pic18f4520 to control an fm25v10 f-ram. I am using compiler v 4.016.
I initially used a hardware spi interface to control the fram, which was simple and straight forward. However, we layed out a board with some traces in the wrong places, so I now need to use a software interface so that I can select which pins are which. I tried to develop a software interface but so far I can't seem to get it to work. I am testing both interfaces with the same setup. One thing I am wonder is, is it a problem to declare a software interface on the same pins that a hardware interface would go on?
For the test I try to write/read both a single character and a string of characters from the fram. In either case with software I get back characters that are all 1's. I know that software spi is slower than hardware, so there is no way I am outrunning the fram. The minimum setup and hold times are not even close to being violated. I don't have a scope with me so I cannot look at what the pic is sending.
This is a serious problem, as we are in a rush to ship our otherwise-working product. I would really appreciate any help anyone could offer. Thanks.
Working hardware interface:
| Code: | #include <18F4520.h>
#device PASS_STRINGS = IN_RAM
#device HIGH_INTS=TRUE
#include <stdio.h>
#include <string.h>
#use delay(INTERNAL=8M, clock=16M)
#fuses INTRC//, DEBUG
//Spi Modes (F-Ram only uses 0 or 3
#define SPI_MODE_0 (SPI_XMIT_L_TO_H | SPI_L_TO_H)
#define SPI_MODE_1 (SPI_L_TO_H)
#define SPI_MODE_2 (SPI_H_TO_L)
#define SPI_MODE_3 (SPI_XMIT_L_TO_H | SPI_H_TO_L)
//F-RAM Commands
#define WREN 0x06
#define WRDI 0x04
#define RDSR 0x05
#define WRSR 0x01
#define READ 0x03
#define FSTRD 0x0B
#define WRITE 0x02
#define SLEEP 0xB9
#define RDID 0x9F
#define SNR 0xC3
#define NO_WR_PROTECT 0x00
struct portb_pin_map {
unsigned short led0;
unsigned short led1;
unsigned short led2;
unsigned short led3;
unsigned short pic_mode;
unsigned short CTS;
unsigned short reserved;
unsigned short bit7;
} portb;
#locate portb = getenv("sfr:PORTB")
struct portc_pin_map {
unsigned short b0;
unsigned short HOLD;
unsigned short SS; // SPI SS -- Place holder.
unsigned short SCK; // SPI SCK -- Place holder.
unsigned short SDI; // SPI SDI -- Place holder.
unsigned short SDO; // SPI SDO -- Place holder.
unsigned short TX; // RS232 TX -- Place holder.
unsigned short RX; // RS232 RX -- Place holder.
} portc;
#locate portc = getenv("sfr:PORTC")
#use rs232(BAUD=9600, XMIT=PIN_A1, RCV=PIN_A0, BITS=8, PARITY=N)
void leds(int a) {
portb.led0=a&1;
portb.led1=(a>>1)&1;
portb.led2=(a>>2)&1;
portb.led3=(a>>3)&1;
}
void tx(char *tx) {
int a=0;
while(tx[a])
putc(tx[a++]);
putc(13);
putc(10);
}
void spi_wr_enable() {
portc.SS=0;
spi_write(WREN);
portc.SS=1;
}
void setup_fram() {
spi_wr_enable();
//write to status register
portc.SS=0;
spi_write(WRSR);
spi_write(0b01000000);
portc.SS=1;
}
void fram_write(int32 adr, char data) {
spi_wr_enable();
//write data
portc.SS=0;
spi_write(WRITE);
spi_write((adr>>16)&1);
spi_write((adr>>8)&0xFF);
spi_write(adr&0xFF);
spi_write(data);
portc.SS=1;
}
void fram_read(int32 adr, char *out, int16 num) {
int16 i=0;
//read data
portc.SS=0;
spi_write(READ);
spi_write((adr>>16)&1);
spi_write((adr>>8)&0xFF);
spi_write(adr&0xFF);
while(num--)
out[i++]=spi_read(0);
out[i]=NULL;
portc.SS=1;
}
void main(void) {
int i=0;
char message[40]="This is just a simple test.";
char result[40];
int32 adr=0;
setup_oscillator(OSC_16MHZ);
delay_ms(1000);
disable_interrupts(global);
set_tris_b(0xF0);
set_tris_c(0xA0);
portc.SS=1;
portc.HOLD=1;
setup_spi (SPI_MASTER | SPI_MODE_0 | SPI_CLK_DIV_4 );
delay_ms(500);
setup_fram();
do {
fram_write(adr++,message[i]);
}
while(message[i++]);
tx(message);
adr=0;
fram_read(adr,result,40);
tx(result);
tx("\r\n");
}
Not working software interface:
#include <18F4520.h>
#device PASS_STRINGS = IN_RAM
#device HIGH_INTS=TRUE
#include <stdio.h>
#include <string.h>
#use delay(INTERNAL=8M, clock=16M)
#fuses INTRC//, DEBUG
//Spi Modes (F-Ram only uses 0 or 3
#define SPI_MODE_0 (SPI_XMIT_L_TO_H | SPI_L_TO_H)
#define SPI_MODE_1 (SPI_L_TO_H)
#define SPI_MODE_2 (SPI_H_TO_L)
#define SPI_MODE_3 (SPI_XMIT_L_TO_H | SPI_H_TO_L)
//F-RAM Commands
#define WREN 0x06
#define WRDI 0x04
#define RDSR 0x05
#define WRSR 0x01
#define READ 0x03
#define FSTRD 0x0B
#define WRITE 0x02
#define SLEEP 0xB9
#define RDID 0x9F
#define SNR 0xC3
#define NO_WR_PROTECT 0x00
struct portb_pin_map {
unsigned short led0;
unsigned short led1;
unsigned short led2;
unsigned short led3;
unsigned short pic_mode;
unsigned short CTS;
unsigned short reserved;
unsigned short bit7;
} portb;
#locate portb = getenv("sfr:PORTB")
struct portc_pin_map {
unsigned short b0;
unsigned short HOLD;
unsigned short SS; // SPI SS -- Place holder.
unsigned short SCK; // SPI SCK -- Place holder.
unsigned short SDO; // SPI SDO -- Place holder.
unsigned short SDI; // SPI SDI -- Place holder.
unsigned short TX; // RS232 TX -- Place holder.
unsigned short RX; // RS232 RX -- Place holder.
} portc;
#locate portc = getenv("sfr:PORTC")
#use rs232(BAUD=9600, XMIT=PIN_A1, RCV=PIN_A0, BITS=8, PARITY=N)
#use spi(MASTER, MSB_FIRST, DI=PIN_C4, DO=PIN_C5, CLK=PIN_C3, BITS=8, MODE=0)
void leds(int a) {
portb.led0=a&1;
portb.led1=(a>>1)&1;
portb.led2=(a>>2)&1;
portb.led3=(a>>3)&1;
}
void tx(char *tx) {
int a=0;
while(tx[a])
putc(tx[a++]);
putc(13);
putc(10);
}
void spi_wr_enable() {
portc.SS=0;
spi_xfer(WREN);
portc.SS=1;
}
void setup_fram() {
spi_wr_enable();
//write to status register
portc.SS=0;
spi_xfer(WRSR);
spi_xfer(0b01000000);
portc.SS=1;
}
void fram_write(int32 adr, char data) {
spi_wr_enable();
//write data
portc.SS=0;
spi_xfer(WRITE);
spi_xfer((adr>>16)&1);
spi_xfer((adr>>8)&0xFF);
spi_xfer(adr&0xFF);
spi_xfer(data);
portc.SS=1;
}
void fram_read(int32 adr, char *out, int16 num) {
int16 i=0;
//read data
portc.SS=0;
spi_xfer(READ);
spi_xfer((adr>>16)&1);
spi_xfer((adr>>8)&0xFF);
spi_xfer(adr&0xFF);
while(num--)
out[i++]=spi_xfer();
out[i]=NULL;
portc.SS=1;
}
void main(void) {
int i=0;
char message[40]="This is just a simple test.";
char result[40];
int32 adr=0;
setup_oscillator(OSC_16MHZ);
delay_ms(1000);
disable_interrupts(global);
set_tris_b(0xF0);
set_tris_c(0xA0);
portc.SS=1;
portc.HOLD=1;
// setup_spi (SPI_MASTER | SPI_MODE_0 | SPI_CLK_DIV_4 );
delay_ms(500);
setup_fram();
do {
fram_write(adr++,message[i]);
}
while(message[i++]);
tx(message);
adr=0;
fram_read(adr,result,40);
tx(result);
tx("\r\n");
} |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Sun May 10, 2009 2:33 pm |
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| I strongly question whether #use spi() works in vs. 4.016. |
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J Hopkins
Guest
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| I didn't know that |
| Posted: Sun May 10, 2009 2:36 pm |
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| PCM programmer wrote: | | I strongly question whether #use spi() works in vs. 4.016. |
Thanks for responding. Are you saying I need to write my own software spi interface? Has someone already written one? I'm not an assembly expert. My background is C/C++. |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Sun May 10, 2009 2:49 pm |
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Don't write it in assembly. Write it in C. Look at some of the CCS
example files for the 25-series eeproms:
| Quote: | | c:\program files\picc\drivers\25640.c |
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