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/*
*
* pwm tester
* The on cycle and off cycles are stored in each PRU's Data memory
*
*/
#include <stdio.h>
#include <stdint.h>
#include <fcntl.h>
#include <sys/mman.h>
#define PRU_ADDR 0x4A300000 // Start of PRU memory Page 184 am335x TRM
#define PRU_LEN 0x80000 // Length of PRU memory
#define PRU0_DRAM 0x00000 // Offset to DRAM
#define PRU1_DRAM 0x02000
#define PRU_SHAREDMEM 0x10000 // Offset to shared memory
#define CYCLES_PER_SECOND 200000000
#define CYCLES_PER_PERIOD (CYCLES_PER_SECOND / 800)
uint32_t *pru0DRAM_32int_ptr; // Points to the start of local DRAM
uint32_t *pru1DRAM_32int_ptr; // Points to the start of local DRAM
uint32_t *prusharedMem_32int_ptr; // Points to the start of the shared memory
/*******************************************************************************
* int start_pwm_count(int ch, int countOn, int countOff)
*
* Starts a pwm pulse on for countOn and off for countOff to a single channel (ch)
*******************************************************************************/
int start_pwm_count(uint32_t duty_cycle) {
uint32_t *pruDRAM_32int_ptr = pru0DRAM_32int_ptr;
uint32_t old_duty_cycle = pruDRAM_32int_ptr[0];
uint32_t old_count_on = (100 - (100 - old_duty_cycle)) * CYCLES_PER_PERIOD / 100;
uint32_t old_count_off = (100 - old_duty_cycle) * CYCLES_PER_PERIOD / 100;
uint32_t new_count_on = (100 - (100 - duty_cycle)) * CYCLES_PER_PERIOD / 100;
uint32_t new_count_off = (100 - duty_cycle) * CYCLES_PER_PERIOD / 100;
printf("old:\n\tcountOn: %d, countOff: %d, count: %d\nnew:\n\tcountOn: %d, countOff: %d, count: %d\n", old_count_on, old_count_off, old_count_off + old_count_on, new_count_on, new_count_off, new_count_off + new_count_on);
// write to PRU shared memory
pruDRAM_32int_ptr[0] = duty_cycle; // On time
return 0;
}
int main(int argc, char *argv[])
{
uint32_t *pru; // Points to start of PRU memory.
int fd;
printf("Servo tester\n");
fd = open ("/dev/mem", O_RDWR | O_SYNC);
if (fd == -1) {
printf ("ERROR: could not open /dev/mem.\n\n");
return 1;
}
pru = mmap (0, PRU_LEN, PROT_READ | PROT_WRITE, MAP_SHARED, fd, PRU_ADDR);
if (pru == MAP_FAILED) {
printf ("ERROR: could not map memory.\n\n");
return 1;
}
close(fd);
printf ("Using /dev/mem.\n");
pru0DRAM_32int_ptr = pru + PRU0_DRAM/4 + 0x200/4; // Points to 0x200 of PRU0 memory
pru1DRAM_32int_ptr = pru + PRU1_DRAM/4 + 0x200/4; // Points to 0x200 of PRU1 memory
prusharedMem_32int_ptr = pru + PRU_SHAREDMEM/4; // Points to start of shared memory
uint32_t desired_duty_cycle = 0;
while (1) {
printf("Enter a duty cycle: ");
scanf("%d", &desired_duty_cycle);
start_pwm_count(desired_duty_cycle);
}
if(munmap(pru, PRU_LEN)) {
printf("munmap failed\n");
} else {
printf("munmap succeeded\n");
}
}
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