Hi, I have written some code in order to activate an SPI interface on my TM4C123GH6PM micro.
#include "tm4c123gh6pm.h"
#include <stdint.h>
void ssi_init(void){
volatile unsigned long delay;
SYSCTL_RCGC1_R |= SYSCTL_RCGC1_SSI0; //activate SSI0
SYSCTL_RCGC2_R |= SYSCTL_RCGC2_GPIOA; //activate clock to PORTA
delay = SYSCTL_RCGC2_R;
GPIO_PORTA_AFSEL_R |= 0x2C; //activate alternate function on PA2,3,5
GPIO_PORTA_PCTL_R = (GPIO_PORTA_PCTL_R&0xFF0F00FF)+0x00202200; //pin control given to SSI0Fss, SSI0Clk and SSI0Tx
GPIO_PORTA_DEN_R |= 0x2C; //enable digital on each pin
SSI0_CR1_R &= ~SSI_CR1_SSE; //disable SSI during config
SSI0_CR1_R &= ~SSI_CR1_MS; //master mode
SSI0_CPSR_R = (SSI0_CPSR_R&~SSI_CPSR_CPSDVSR_M)+2; //8MHZ
SSI0_CR0_R &= ~(SSI_CR0_SCR_M | SSI_CR0_SPH | SSI_CR0_SPO); //Freescale SPH=SPO=0
SSI0_CR0_R = (SSI0_CR0_R&~SSI_CR0_FRF_M)+SSI_CR0_FRF_MOTO;
SSI0_CR0_R = (SSI0_CR0_R&~SSI_CR0_DSS_M)+SSI_CR0_DSS_8; //Frame length is 8-bit
SSI0_CR1_R |= SSI_CR1_SSE; //enable SSI
}
void data_send(unsigned char data){
while((SSI0_SR_R&0x00000002)==0){}; //Wait for buffer
SSI0_DR_R = data; //send data
}
int main(void){
unsigned char data = 0xAA;
ssi_init();
while(1){
data_send(data);
}
}
The file contains an initialisation routine which was created using the databook and examples from Jonathan Valvano's book as a general guide. There is a second routine which places the test data into the SSI_DR register. To test it I i initialised a test frame and then just repeatedly call the data send routine.
Now my thoughts are that I should be able to see the pin change on SSIClk, SSITx and SSIFss using an oscilloscope but clearly I am doing something wrong because I can't see anything. Is it the code or my method of testing the interface or both. All help is greatly appreciated.
