Styjun

We are trying to set up SPI communication between a pic32 and an ADS1298. The issue is that we cannot get the clock set up correctly.

What I have tried is the following

#include <xc.h>
#include "SDlib16.h"
#pragma config FNOSC = FRCPLL // Oscillator selection
#pragma config POSCMOD = HS // Primary oscillator mode
#pragma config FPLLIDIV = DIV_2 // PLL input divider (8 -> 4)
#pragma config FPLLMUL = MUL_20 // PLL multiplier ( 4x20 = 80)
#pragma config FPLLODIV = DIV_1 // PLL output divider
#pragma config FPBDIV = DIV_2 // Peripheral bus clock divider 80/ 2= 40 mhz
#pragma config FSOSCEN = OFF // Secondary oscillator enable

#pragma config IESO=OFF 
#pragma config FCKSM=CSDCMD
#pragma config OSCIOFNC=OFF

#pragma config FWDTEN = OFF // Watchdog timer enable
#pragma config WDTPS = PS4096 // Watchdog timer post-scaler
#pragma config FSRSSEL = PRIORITY_7 // SRS interrupt priority


/*
 * 
 */
void configpins(void)

 DDPCONbits.JTAGEN = 0;//Turns off the JTAG function of all pins
 AD1PCFG=0xFFFF;//Turns off the analog function of all pins
 TRISBbits.TRISB8=0; //Makes RB8 an output (Chip select)
 TRISBbits.TRISB12=0;//Makes RB12 an output(Hold)
 TRISBbits.TRISB10=0;//Makes RB10 an output(Write protect)

void initialSPI(void)

 IEC0CLR=0x03800000;//turns off SPI interrupts 
 SPI4CONbits.ON=0;//turns off SPI4 module
 SPI4BUF=0;//Sets SPI4 buffer to 0
 SPI4CONbits.ENHBUF=0;//Sets ENHBUF to zero
 SPI4CONbits.CKP=0;//Sets clock phase bit to 0
 SPI4BRG=0;//Sets the SPI clock to be at 20MHz(Logic analyzer cant sample high enough for 20MHz )
 SPI4STATbits.SPIROV=0;//Sets overflow bit to zero
 SPI4CONbits.MSTEN=1;//Sets microcontroller to master mode
 SPI4CONbits.DISSDO=0;//Sets the module to control the SDO pin
 SPI4CONbits.CKE=1;//Sets the clock edge bit to 1
 SPI4CONbits.SMP=0;//Sets SMP bit to 0

 SPI4CONbits.MODE16=0;//Turns off 16bit mode
 SPI4CONbits.MODE32=0;//Turns off 32bit mode
 SPI4CONbits.ON=1;// Turns on SPI4 module


unsigned char Transfer(unsigned char data)
 
 SPI4STATbits.SPIRBF=0; //Clears the receives buffer bit 
 SPI4BUF = data;//Puts data into the buffer
 SPI4STATbits.SPITBE=0;//Turns off buffer enable 
 while (!SPI4STATbits.SPIRBF);//While the Receive buffer flag is empty
 return SPI4BUF; // read a byte



unsigned char SPITransaction(unsigned char data)//Simple one byte in and one out

 PORTBbits.RB8=0;//clears the chip select
 unsigned char CharReturned=Transfer(data);// Calls the transfer function to send byte to buffer
 PORTBbits.RB8=1;//Sets the chip select
 return CharReturned;//Returns the byte received from buffer


void ReadDevice(void)//Gets the Device ID

 PORTBbits.RB8=0;//Clears the chip select
 Transfer(0xAB);//Bytes to get the device id
 Transfer(0x00);
 Transfer(0x00);
 Transfer(0x00);
 Transfer(0x00);
 Transfer(0x00);
 PORTBbits.RB8=1;//Sets the Device ID

int main(int argc, char** argv) 

 configpins();
 initialSPI();
 PORTBbits.RB10=1;//Sets the Write protect to high
 PORTBbits.RB12=1;//Sets Hold to high
 PORTBbits.RB0=0;
 while(1)// Forever loop
 
 //unsigned char Result=SPITransaction('W');//Sends W to the buffer and gets back a byte
 //ReadDevice();//Gets the Device ID
 PORTBbits.RB8=0;//Clears the chip select
 Transfer(0x08);//Bytes to get the device id
 PORTBbits.RB8=1;//Sets the Device ID
 
 return (EXIT_SUCCESS);

I do not know what am i doing wrong, when I hook up the clock to a logic analyzer, it does not look like a clock, instead it looks like something completely random anyone knows what am I doing wrong?

I think you have missed to set the SCK (clock) as output.