Has anyone encountered problems getting SPI up and running on a PIC? I'm using a PIC16LF1827 and am trying to output data via SPI to what will eventually be an LCD graphics screen. The PIC will be the Master.
Attached is a picture of what I'm seeing on the SPI port pins (via Salae Logic Analyzer). I figure there must be something wrong in either my configuration or there is some flag or bit that needs to be checked before I can write successfully to SSP1BUF register.
Also this is source code that generated the waveforms.
/************************
This is a module to initialize the PIC16LF1827 to communicate with
the Nokia 5110 graphical LCD screen. I'm going to draw something.
author: Osagie Igbeare
8/7/2014
*************************/
/**************** Header Files *********************/
#include "BitDefs.h"
//#include <htc.h>
#include <xc.h>
#include "pic.h"
#include "chip_select.h"
/***************** Configuration Macros ***************/
//__CONFIG(FCMEN_OFF & IESO_OFF & FOSC_LP & WDTE_OFF & MCLRE_ON & PWRTE_OFF & BOREN_OFF
// & LVP_ON & WRT_OFF & CPD_OFF & CP_OFF);
// #pragma config statements should precede project file includes.
// Use project enums instead of #define for ON and OFF.
// CONFIG1
#pragma config FOSC = LP // Oscillator Selection (LP Oscillator, Low-power crystal connected between OSC1 and OSC2 pins)
#pragma config WDTE = OFF // Watchdog Timer Enable (WDT disabled)
#pragma config PWRTE = OFF // Power-up Timer Enable (PWRT disabled)
#pragma config MCLRE = ON // MCLR Pin Function Select (MCLR/VPP pin function is MCLR)
#pragma config CP = OFF // Flash Program Memory Code Protection (Program memory code protection is disabled)
#pragma config CPD = OFF // Data Memory Code Protection (Data memory code protection is disabled)
#pragma config BOREN = OFF // Brown-out Reset Enable (Brown-out Reset disabled)
#pragma config CLKOUTEN = ON // Clock Out Enable (CLKOUT function is enabled on the CLKOUT pin)
#pragma config IESO = OFF // Internal/External Switchover (Internal/External Switchover mode is disabled)
#pragma config FCMEN = OFF // Fail-Safe Clock Monitor Enable (Fail-Safe Clock Monitor is disabled)
// CONFIG2
#pragma config WRT = OFF // Flash Memory Self-Write Protection (Write protection off)
#pragma config PLLEN = OFF // PLL Enable (4x PLL enabled)
#pragma config STVREN = ON // Stack Overflow/Underflow Reset Enable (Stack Overflow or Underflow will cause a Reset)
#pragma config BORV = LO // Brown-out Reset Voltage Selection (Brown-out Reset Voltage (Vbor), low trip point selected.)
#pragma config LVP = ON // Low-Voltage Programming Enable (Low-voltage programming enabled)
/***************** # Defines *****************/
#define lcd_data BIT3HI
#define lcd_command BIT3LO
#define hangTime 1000
/*************** module level variables ************/
static char counter;
int x;
int i = 0;
char dummy;
static char LCD_Init[6];
/******* Function Prototypes ***************/
void InitPorts(void);
void InitTimers(void);
void InitInterrupts(void);
void InitComm(void);
void NokiaInit(void);
void Delay(int waitTime);
void SightPin_B0(void);
/******* Acutal Functions ****************/
void InitPorts()
{
ANSELA = 0x00; // Port A pins are digital
ANSELB = 0x00; // Port B pins are digital
TRISA = 0b11111010; // 1 - input, 0 - output, RA2, RA0 are outputs
TRISB = 0b10000010; // 1 - input, 0 - output, RB0, RB2 - RB6 is an output
PORTA = 0b11111111; // initialize LED to OFF
PORTB = 0b11111111;
//OSCCON = 0x68;
APFCON0 = 0x00;
}
void InitTimers()
{
T2CON = 0b01111110; // Fosc / (4 instruct * 16 prescale * 16 postscale * 60 PR2) = 65 Hz
PR2 = 1;
}
void InitInterrupts()
{
PIE1 = 0b00000010; // Enable TMR2IE, interrupt when Timer 2 matches PR2
// Enable SSP1IE, interrupt for MSSP1 (aka SPI1)
// Bit 3 high - enable MSSP interrupt
INTCON = 0b11000000; // Enable GIE, Enable PEIE
}
void InitComm()
{
// setup SPI-1 (aka SSP) to communicate with Nokia LCD screen
SSP1ADD = 0; // Baud Rate = Fosc / ((SSP1ADD + 1)(4))
// since Fosc = 4 MHz, Baud Rate = 1 MHz
// since SSP1ADD = 0 is not supported same timing is achieved
// by setting bits <3:0> of SSPM all to 0's (see below)
SSP1STATbits.SMP = 0; // data on rising edge, data @ middle
SSP1CON1bits.WCOL = 0; // no collision
SSP1CON1bits.SSPOV = 0; // no overflow
SSP1CON1bits.CKP = 1; // idle high
SSP1STATbits.CKE = 1; // sample even edges
SSP1CON1bits.SSPM3 = 0; // Set LF1827 as Master, clock rate Fosc / 4
SSP1CON1bits.SSPM2 = 0;
SSP1CON1bits.SSPM1 = 0;
SSP1CON1bits.SSPM0 = 0;
SSP1CON1bits.SSPEN = 1; // SSP Enable
}
void NokiaInit()
{
i = 0;
// LCD_Init array populated with initialization sequence
LCD_Init[0] = 0x21; // tell LCD extended commands to
LCD_Init[1] = 0xB0; // set LCD Vop (contrast) ** parameter to mess with if screen doesn't display ****
LCD_Init[2] = 0x04; // set temp coefficient
LCD_Init[3] = 0x13; // LCD Bias mode 1:48 (if not working, try 0x13)
LCD_Init[4] = 0x20; // back to regular commands
LCD_Init[5] = 0x0C; // enable normal display (dark on light), horiz addressing
// initialization sequence for the PCD8544 driver on the Nokia LCD
// beginning with RESET
/*
PORTA &= BIT0LO;
Delay(hangTime);
PORTA |= BIT0HI;
*/
PORTB &= lcd_command; // tell LCD commands are coming
PORTB &= BIT5LO; // lower SCE line to begin transmission
//SightPin_B0();
//PIR1bits.SSP1IF = 0;
SSP1CON1bits.WCOL = 0;
SSP1BUF = 0xC3;
while (!SSP1STATbits.BF); // wait for buffer to be full
/*
if(SSP1CON1bits.WCOL == 0)
{
SSP1BUF = 0xC3;
}
*/
/*
SSP1BUF = 0x21; // tell LCD extended commands to
SSP1BUF = 0xB0;
SSP1BUF = 0x04;
SSP1BUF = 0x13;
SSP1BUF = 0x20;
SSP1BUF = 0x0C;
*/
PORTB |= BIT5HI; // raising SCE line at the end of transmission0
}
void interrupt ISR()
{
counter++;
if (TMR2IF)
{
if ((counter % 2) != 0)
{
PORTA |= BIT2HI;
//PORTB &= BIT6LO;
}
else
{
PORTA &= BIT2LO;
//PORTB |= BIT6HI;
counter = 0;
}
TMR2IF = 0; // clears the TIMR2IF (timer 2 interrupt flag)
}
/*
if (SSP1IF)
{
if (i < 6)
{
SSP1BUF = LCD_Init[i];
i++;
SightPin_B0();
}
SSP1BUF = LCD_Init[i];
SSP1IF = 0;
}
*/
return;
}
void Delay(int waitTime)
{
x = 0;
while(x < waitTime)
{
x += 1;
}
}
/***********************************************************/
/******************** Debugging Library ********************/
void SightPin_B0(void)
{
// toggles pin B0 for debugging purposes
if ((PORTB & BIT0HI) == BIT0HI)
{
PORTB &= BIT0LO;
}
else
{
PORTB |= BIT0HI;
}
}
/********************************************************/
/******** Main - which actually runs the code ***********/
/********************************************************/
void main ()
{
// Initializing PIC16LF1827
InitPorts();
Thanks for your help.
RESOLUTION:
So it seems that I had to wait for the Buffer Full Flag to be clear before raising the SS line to signal the end of a transmission.
If anyone has experience with Salae, you know they usually display the hex values of the bytes that are on the line. I was wondering why this wasn't the case here. It turns out that when enabling the SPI under "Analyzers" all 4 lines need to be dedicated to some channel, even if that one channel isn't being used (in my case, I wasn't using the MISO line since I intend for one way communication with a graphic LCD screen - Nokia 5110 with PCD8544 driver to be more exact).
