Something odd I'm just now noticing is that GPI on the beaglewbone seems to
have some lag.
What I'm doing:We have a cape with 6 channels PWM, 6 pins input, and
several pins output. In order to test the PWM circuitry on our capes, I'm
configuring these pins as GPO's, and we have a test header that ties the
PWM pins to the input pins. All this is configured via an overlay file, and
it is all correct. Additionally, we have LEDs on each channel PWM on these
headers for visual inspection. The LEDs light up correctly when the PWM
pins( again configured as GPO's for the purpose of this test ) are high.
However, when setting these pins high, then reading back the value from the
PWM pins, and input pins, The input pins lag behind a great deal. Code:
#include <unistd.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <stdio.h>
#include <errno.h>
#include <stdlib.h>
#define HIGH 1
#define LOW 0
#define PWM1 2
#define PWM2 3
#define PWM3 50
#define PWM4 22
#define PWM5 51
#define PWM6 23
#define Z1IN 44
#define Z2IN 45
#define Z3IN 46
#define Z4IN 47
#define Z5IN 48
#define Z6IN 49
void set_pin(int pin_num, int value)
{
char gpio_path[40] = {0};
char str_value[2] = {0};
sprintf(str_value, "%d", value);
sprintf(gpio_path, "/sys/class/gpio/gpio%d/value", pin_num);
int fd = open(gpio_path, O_WRONLY);
if(fd == -1){
perror(gpio_path);
exit(1);
}
int nread = write(fd, str_value, 1);
if( nread < 0){
perror("write()");
exit(1);
}
close(fd);
}
int get_pin(int pin_num)
{
char gpio_path[40] = {0};
char str_value[2] = {0};
sprintf(gpio_path, "/sys/class/gpio/gpio%d/value", pin_num);
int fd = open(gpio_path, O_RDONLY);
if(fd == -1){
perror(gpio_path);
exit(1);
}
read(fd, str_value, sizeof(str_value - 1));
close(fd);
return strtol(str_value, NULL, 10);
}
int main()
{
set_pin(PWM1, LOW);
set_pin(PWM2, LOW);
set_pin(PWM3, LOW);
set_pin(PWM4, LOW);
set_pin(PWM5, LOW);
set_pin(PWM6, LOW);
sleep(1);
printf("PWM1: %i Z1IN: %i \n", get_pin(PWM1), get_pin(Z1IN));
printf("PWM2: %i Z2IN: %i \n", get_pin(PWM2), get_pin(Z2IN));
printf("PWM3: %i Z3IN: %i \n", get_pin(PWM3), get_pin(Z3IN));
printf("PWM4: %i Z4IN: %i \n", get_pin(PWM4), get_pin(Z4IN));
printf("PWM5: %i Z5IN: %i \n", get_pin(PWM5), get_pin(Z5IN));
printf("PWM6: %i Z6IN: %i \n", get_pin(PWM6), get_pin(Z6IN));
printf("\n");
/***********************************************************/
set_pin(PWM1, HIGH);
set_pin(PWM2, HIGH);
set_pin(PWM3, HIGH);
set_pin(PWM4, HIGH);
set_pin(PWM5, HIGH);
set_pin(PWM6, HIGH);
sleep(1);
printf("PWM1: %i Z1IN: %i \n", get_pin(PWM1), get_pin(Z1IN));
printf("PWM2: %i Z2IN: %i \n", get_pin(PWM2), get_pin(Z2IN));
printf("PWM3: %i Z3IN: %i \n", get_pin(PWM3), get_pin(Z3IN));
printf("PWM4: %i Z4IN: %i \n", get_pin(PWM4), get_pin(Z4IN));
printf("PWM5: %i Z5IN: %i \n", get_pin(PWM5), get_pin(Z5IN));
printf("PWM6: %i Z6IN: %i \n", get_pin(PWM6), get_pin(Z6IN));
return 0;
}
As anyone can see, really simple straight forward code. The sleep shown in
the code is required at this value, and if lowered, the input pins will be
set correctly, but will read wrong. So here's the output as it stands.
root@wgd:~/dl-i2c-test# nano read_zonein.c
root@wgd:~/dl-i2c-test# gcc -Wall -o read_zonein read_zonein.c
root@wgd:~/dl-i2c-test# ./read_zonein
PWM1: 0 Z1IN: 1
PWM2: 0 Z2IN: 1
PWM3: 0 Z3IN: 1
PWM4: 0 Z4IN: 1
PWM5: 0 Z5IN: 1
PWM6: 0 Z6IN: 1
PWM1: 1 Z1IN: 0
PWM2: 1 Z2IN: 0
PWM3: 1 Z3IN: 0
PWM4: 1 Z4IN: 0
PWM5: 1 Z5IN: 0
PWM6: 1 Z6IN: 0
But change the sleep() value to .5( 500 ms ) . . .
root@wgd:~/dl-i2c-test# nano read_zonein.c
root@wgd:~/dl-i2c-test# gcc -Wall -o read_zonein read_zonein.c
root@wgd:~/dl-i2c-test# ./read_zonein
PWM1: 0 Z1IN: 1
PWM2: 0 Z2IN: 1
PWM3: 0 Z3IN: 1
PWM4: 0 Z4IN: 1
PWM5: 0 Z5IN: 1
PWM6: 0 Z6IN: 1
*PWM1: 1 Z1IN: 1PWM2: 1 Z2IN: 1*
PWM3: 1 Z3IN: 0
PWM4: 1 Z4IN: 0
PWM5: 1 Z5IN: 0
PWM6: 1 Z6IN: 0
Change the sleep value to .2(200 ms ), and the executed code gets all kinds
of squirely. e.g. very inconsistent.
Does anyone know what's going on here ?
root@wgd:~/dl-i2c-test# uname -r
4.4.55-ti-r94
root@wgd:~/dl-i2c-test# free
total used free shared buffers cached
Mem: 499308 64736 434572 1456 5792 32348
-/+ buffers/cache: 26596 472712
Swap: 0 0 0
root@wgd:~/dl-i2c-test# uptime
15:57:39 up 2:33, 1 user, load average: *0.00, 0.01, 0.00*
root@wgd:~/dl-i2c-test# cat /etc/dogtag
BeagleBoard.org Debian Image 2017-04-02
Even for a non RT kernel this seems ridiculously slow
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