Code: Select all
#!/usr/bin/python
# Toggle GPIO pin 23.
# Output pulse frequency is about 18 kHz (varies due to other activity).
pin_path = '/sys/class/gpio/gpio23'
def write_once(path, value):
f = open(path, 'w')
f.write(value)
f.close()
return
# Set pin for output, with initial value low.
write_once(pin_path + '/direction', 'out\n')
f = open(pin_path + '/value', 'w')
# Blink as fast as possible...
while 1:
f.write('1')
f.flush()
f.write('0')
f.flush()
f.close()
* Toggle GPIO pin 23 as fast as possible.
GPIO 23 must be exported before this program runs.
Once exported, file permissions for the gpio23 direction and value
files must be set appropriately, if user is not root.
Output pulse frequency is 120 kHz (typically varies a few kHz due to other activities such as network traffic, clock maintenence, etc.).
*/
Code: Select all
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
int main()
{
int fd, fd2;
fd = open("/sys/class/gpio/gpio23/value", O_RDWR);
if (fd < 0)
{
perror("Open value failed");
exit(2);
}
fd2 = open("/sys/class/gpio/gpio23/direction", O_RDWR);
if (fd2 < 0)
{
perror("Open direction failed");
exit(2);
}
else
{
if (3 != write(fd2, "out", 3))
{
perror("Write direction failed");
exit(2);
}
close(fd2);
}
while (1)
{
if (0 > write(fd, "1", 1))
{
perror("Write 1 failed");
exit(3);
}
if (0 > write(fd, "0", 1))
{
perror("Write 0 failed");
exit(3);
}
}
return 0;
}
