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iso9001
Joined: 02 Dec 2003 Posts: 262
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Erratic SPI with 16F876A and MCP2515 |
Posted: Sun Feb 19, 2006 10:32 pm |
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Hi all,
I'm having some pretty big problems getting the SPI interface working. It seems I reset the 2515, read in CANCTRL and get 00, do another read and get 0x87, one more and I get 00 again. Somtimes that first 00 is an 0xFF.
I'de say maybe I'm having clock issues, but I'm using a 10MHz ceramic res with built in caps on the 2515 and a 20MHz version on the 16F876A pic. The pic seems stable. I don't have a scope of course
Its REALLY frustrating.
Wondering if anyone had a similar problem or have any ideas,
Here some of the code I'm using:
Code: |
void ResetMCP2515(void)
{
output_high(MCP2515_CS);
output_low(MCP2515_RESET_PIN);
delay_us(10);
output_high(MCP2515_RESET_PIN);
delay_ms(0);
}
int ReadRegister(int regaddr)
{
output_low(MCP2515_CS);
spi_write(READCMD);
spi_write(regaddr);
rreg = spi_read(0);
output_high(MCP2515_CS);
return(rreg);
}
int data=0;
int data2=0;
int data3=0;
void main()
{
setup_spi(SPI_MASTER | SPI_H_TO_L | SPI_XMIT_L_TO_H);
ResetMCP2515();
data3 = ReadRegister(CANCTRL);
data2= ReadRegister(CANCTRL);
data = ReadRegister(CANCTRL);
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I've written it a few different ways. This code is borrowed from another post I saw.
Thanks in advance! [/code] |
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iso9001
Joined: 02 Dec 2003 Posts: 262
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Posted: Sun Feb 19, 2006 11:20 pm |
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Here is my entire (crappy) code. Maybe there is somthing I'm missing.
Output: Which now seems to be pretty stable
Code: |
Resetting CAN
Reading STAT : 80
Reading STAT : 0b
Reading STAT : 0f
Reading STAT : 03
Reading STAT : 03
Setting CTRL to 0x0F
Reading STAT : 00
Reading CTRL : 00
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Program:
Code: |
#include <16F876A.h>
#device ICD=TRUE
#fuses HS,NOLVP,NOWDT,NOPROTECT, PUT, NOBROWNOUT
#use delay(clock=20000000)
#use rs232(DEBUGGER)
#define CS PIN_A4
#define RESET PIN_A3
#define READCMD 0x03
#define WRITECMD 0x02
#define CANCTRL 0x0F
#define CANSTAT 0x0E
int data=99;
int tempdata,temp;
void CANReset(void)
{
output_low(RESET);
delay_us(10);
output_high(RESET);
}
void CANWrite(int addr, int value)
{
output_low(CS);
spi_write(WRITECMD);
spi_write(addr);
spi_write(value);
output_high(CS);
}
int CANRead(int addr)
{
output_low(CS);
spi_write(READCMD);
spi_write(addr);
tempdata = spi_read(0);
output_high(CS);
return(tempdata);
}
void main() {
output_high(CS); //Start CS high
setup_spi(SPI_MASTER | SPI_L_TO_H | SPI_XMIT_L_TO_H );
printf("Resetting CAN\n");
CANReset();
printf("Reading STAT ");
data = CANRead(CANSTAT);
printf(": %2x\n", data);
printf("Reading STAT ");
data = CANRead(CANSTAT);
printf(": %2x\n", data);
printf("Reading STAT ");
data = CANRead(CANSTAT);
printf(": %2x\n", data);
printf("Reading STAT ");
data = CANRead(CANSTAT);
printf(": %2x\n", data);
printf("Reading STAT ");
data = CANRead(CANSTAT);
printf(": %2x\n", data);
printf("Setting CTRL to 0x0F\n");
CANWrite(CANCTRL, 0x80);
delay_ms(10);
printf("Reading STAT ");
data = CANRead(CANSTAT);
printf(": %2x\n", data);
printf("Reading CTRL ");
data = CANRead(CANCTRL);
printf(": %2x\n", data);
while (1) { }
}
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I'm very stuck. |
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PCM programmer
Joined: 06 Sep 2003 Posts: 21708
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Posted: Mon Feb 20, 2006 12:58 am |
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One question to ask before looking at anything else, is do you have
a pull-up resistor on Pin A4 ? |
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iso9001
Joined: 02 Dec 2003 Posts: 262
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Posted: Mon Feb 20, 2006 3:08 am |
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No,
I'm pulling it high then low then high again from the pic................
Oh sh!t ! IT GOT ME AGAIN!!!!!!!! ARRRRRRRR I AM SOOO FREAKING STUPID!!!
I H A T E THE A4 PIN!!!!
Seriously.... I'm a retarded desk rabbit !
I had it on A5 but when that was going on my code was crappy and it didn't anyway. So I moved it up one and didn't even think about it.
Thank You PCM, good catch. I'll try that tomorrow. |
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