I have to read a pair of encoders, and is not possible to use an interrupt, because the frequency of the input signal is too high (Encoder) and the microcontroller is busy all the time to answer the interrupts generated. In this case, I need to use a polling technique by reading an accumulator register every “x” milliseconds. I think the TIMER0 and PORTB configuration is correct, but the “TIMER0_TAV_R” remain at zero all the time...Can you help me? Where is the mistake?
Here is my code:
// external signal connected to PB6 (T0CCP0) (trigger on rising edge)
#include <stdint.h>
#include "..\tm4c123gh6pm.h"
#include "PLL.h"
void EdgeCounter_Init(void){
int delay;
SYSCTL_RCGC1_R |= SYSCTL_RCGC1_TIMER0; // activate timer0
SYSCTL_RCGC2_R |= SYSCTL_RCGC2_GPIOB; // activate port B
delay = SYSCTL_RCGC2_R; // allow time for clock to start
GPIO_PORTB_DIR_R &= ~0x40; // make PB6 input (encoder input pulses)
GPIO_PORTB_DEN_R |= 0x40; // enable digital I/O on PB6
GPIO_PORTB_AFSEL_R |= 0x40; // enable alternate function on PB6
GPIO_PORTB_PCTL_R &= ~0x0F000000; // configure PB6 as TIMER
GPIO_PORTB_PCTL_R |= 0x07000000;
GPIO_PORTB_AMSEL_R &= ~0x40; // disable analog functionality on PB6
TIMER0_CTL_R &= ~TIMER_CTL_TAEN; // disable timer0A during setup
TIMER0_CFG_R = TIMER_CFG_16_BIT; // configure for 16-bit timer mode
TIMER0_TAMR_R = (TIMER_TAMR_TACMR|TIMER_TAMR_TAMR_CAP); // configure for capture mode
TIMER0_CTL_R &= ~(TIMER_CTL_TAEVENT_POS|0xC); // configure for rising edge event
TIMER0_TAILR_R = 0x00000000; // start value
TIMER0_CTL_R |= TIMER_CTL_TAEN; // enable timer0A 16-b
}
int main(void){
unsigned int CounterValue = 0;
PLL_Init();
EdgeCounter_Init(); // initialize GPIOB and TIMER0A
while(1){
CounterValue = TIMER0_TAV_R; //Counter Value
}
}
