Terrible time getting SPI to work w/16F872

ECACE · Joined: 24 Jul 2006 Posts: 94

I have been spending the last two days trying to get SPI to work on my project to no avail. I am using a 16F872 running a cutter module, connecting to a printer that will communicate with this board. When the printer powers up, it checks each of the SPI ports and expects the board to reply with its HW ID byte.
When I run the code with the printer, I have a logic analyser connected, so I can see what is happening on all the lines. I see the point where the CS goes low and it is clocked 8 times, but SDI and SDO are silent. I have followed the circuit from them printer MLB to this new module and all the HW seems to be working fine, but SPI is not happy.
Is there somthing stupid simple I am missing here??? Using PCWH 3.227
I have stripped the code down to just the SPI section trying to get it to work. Mind you, I am a HW engineer trying to learn C, so pardon my messy code! Here it is:

#include <16F872>
#device ICD=TRUE
#device adc=8
#include <stdio>
#ZERO_RAM

#FUSES NOWDT //No Watch Dog Timer
#FUSES HS //High speed Osc (> 4mhz)
#FUSES PUT //Power Up Timer
#FUSES NOPROTECT //Code not protected from reading
#FUSES DEBUG //Debug mode for use with ICD
#FUSES NOBROWNOUT //No brownout reset
#FUSES LVP //Low Voltage Programming on B3(PIC16) or B5(PIC18)
#FUSES NOCPD //No EE protection
#FUSES NOWRT //Program memory not write protected

#use delay(clock=20000000)
#use rs232(baud=9600,parity=N,xmit=PIN_C6,rcv=PIN_C7,bits=9)

#define PORTA = 5
#define PORTB = 6
#define PORTC = 7

#INT_SSP
void SPIInterupt()
{
printf("You are in the SPI Interupt!"); //Never gets here
}

void main()
{
////////////////////////////////////////////////////////////////////////////////
// Variables and Constants //
////////////////////////////////////////////////////////////////////////////////

int spi_data_in, spi_data_out, spi_id=3;
//spi_data_in == data from the mlb to cutter
//spi_data_out == data from the cutter to mlb
//spi_id == hardware id of the cutter module

////////////////////////////////////////////////////////////////////////////////
// Configure pin direction //
////////////////////////////////////////////////////////////////////////////////

set_tris_a(0b11111111); //7-0-All inputs
set_tris_c(0b01011000); //7-out,6-in,5-out,4-in,3-in,2-out,1-out,0-out

////////////////////////////////////////////////////////////////////////////////
// Periferal Setup //
////////////////////////////////////////////////////////////////////////////////

setup_adc_ports(NO_ANALOGS);

setup_spi(SPI_SLAVE|SPI_L_TO_H);

setup_timer_0(RTCC_INTERNAL|RTCC_DIV_1);
setup_timer_1(T1_DISABLED);
setup_timer_2(T2_DIV_BY_4,24,1);

setup_ccp1(CCP_PWM);

enable_interrupts(GLOBAL);

////////////////////////////////////////////////////////////////////////////////
// Simple Spi Test //
////////////////////////////////////////////////////////////////////////////////

printf("Out of reset and sending ID\n\n"); //Works!
spi_write(spi_id); //Never sends it out but will pass and go to printf
// spi_data_in = spi_read(spi_id); //Never sends it out but will pass and go to printf
printf("ID has been sent!!!");

while(1)
{
printf("sitting in main loop\n\f");
}
}
_________________
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PCM programmer · Joined: 06 Sep 2003 Posts: 21708

Change the LVP fuse to NOLVP and look at this sample code:
http://www.ccsinfo.com/forum/viewtopic.php?t=26888

ECACE · Joined: 24 Jul 2006 Posts: 94

Ok, I made a couple changes and can get SPI to communicate, as long as I don't mess with any other pins of PORTC. I can run SPI communications fine, as long as I don't mess with the CCP or RS-232 BEFORE I try to do my SPI comms. If I enable the CCP and/or try to send anything with RS-232, then the SPI port seems to get messed up.
What am I missing here??? Thanks for the help so far, and any other help given.

#include <16F872>
#device ICD=TRUE
#device adc=8

#FUSES NOWDT //No Watch Dog Timer
#FUSES HS //High speed Osc (> 4mhz)
#FUSES PUT //Power Up Timer
#FUSES NOPROTECT //Code not protected from reading
#FUSES DEBUG //Debug mode for use with ICD
#FUSES NOBROWNOUT //No brownout reset
#FUSES NOLVP //No Low Voltage Programming on B3(PIC16) or B5(PIC18)
#FUSES NOCPD //No EE protection
#FUSES NOWRT //Program memory not write protected

#use delay(clock=8000000)
#use rs232(baud=9600,parity=N,xmit=PIN_C6,rcv=PIN_C7,bits=9)

#define PORTA = 5
#define PORTB = 6
#define PORTC = 7
#define SPI_SS PIN_A5
#define SPI_CLK PIN_C3
#define SPI_DI PIN_C4
#define SPI_DO PIN_C5

#ZERO_RAM

void main()
{
////////////////////////////////////////////////////////////////////////////////
// Variables and Constants //
////////////////////////////////////////////////////////////////////////////////

int spi_data_in, spi_data_out, spi_id=3;
//spi_data_in == data from the mlb to cutter
//spi_data_out == data from the cutter to mlb
//spi_id == hardware id of the cutter module

////////////////////////////////////////////////////////////////////////////////
// Configure pin direction //
////////////////////////////////////////////////////////////////////////////////

set_tris_a(0b11111111); //7-0-All inputs
set_tris_c(0b01011000); //7-out,6-in,5-out,4-in,3-in,2-out,1-out,0-out

////////////////////////////////////////////////////////////////////////////////
// Periferal Setup //
////////////////////////////////////////////////////////////////////////////////

setup_adc_ports(NO_ANALOGS);
setup_adc(ADC_OFF);

setup_spi(SPI_SLAVE|SPI_L_TO_H);

setup_timer_0(RTCC_INTERNAL|RTCC_DIV_1);
setup_timer_1(T1_DISABLED);
setup_timer_2(T2_DIV_BY_4,24,1);
// setup_ccp1(CCP_PWM); //If left in, SPI won't work!
// enable_interrupts(GLOBAL);

// printf("Waiting to send ID Byte...\n\f"); //If left in, SPI won't work!
spi_write(spi_id);
printf("\n\fID Byte 1 & 2 have been sent...now sitting idle!");

while(1)
{

}
}
_________________
A HW Engineer 'trying' to do SW !!! Run!!!

PCM programmer · Joined: 06 Sep 2003 Posts: 21708

ECACE · Joined: 24 Jul 2006 Posts: 94

I did #1 and it worked!!! Thank you so much for your help. Why would that box hav not been checked? Can that cause other problems? Also, how can I find more information about the device editor and what some of the other boxes meant? Thanks again for your help.
_________________
A HW Engineer 'trying' to do SW !!! Run!!!

PCM programmer · Joined: 06 Sep 2003 Posts: 21708

I think it's been that way for years. I checked vs. 3.191 and it has the
bug. Probably, very few people use the 16F872 and so it was never
noticed until now. I think it was just an accident (an oversight) that
occurred when the chip data was initially entered.

Historically, CCS doesn't really check things very well when they add
support for a new PIC. Quite often the start-up code is incorrect and
the A/D functions or comparator functions may have errors. Lately
they've increased the size of their company, so hopefully they've added
more staff to check these kinds of things.

Since I don't have PCW or PCWH (I only have PCM and PCH), I can't
offer much help on the Device Editor. (Only what I can see on the
screen-shot).

ECACE · Joined: 24 Jul 2006 Posts: 94

OK. Well, it sure is a good thing there is this forum. I was about to loose hair a couple of hours ago. 8-0
Hopefully this project will go smoother from this point on. Thanks again guys/gals for all your help.
_________________
A HW Engineer 'trying' to do SW !!! Run!!!