Negens: Migrated comment #933

2020-05-02T05:28:57Z

Migrated comment #933

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Hello,

After digging a lot, I made it.
Forget the raspi-gpio program. I could never install it because of the messy buggy nodejs package.

Here is the method I used :

Create a file "gpio_alt.c" :

======================================================

/*
Utility to switch Raspberry-Pi GPIO pin functions
Tim Giles 01/04/2013

Usage:
$ gpio_alt -p PIN_NUMBER -f ALT_NUMBER

Based on RPi code from Dom and Gert, 15-Feb-2013, <http://elinux.org/RPi_Low-level_peripherals#C_2>
and Gnu getopt() example <http://www.gnu.org/software/libc/manual/html_node/Example-of-Getopt.html#Example-of-Getopt>
*/

#include <ctype.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/mman.h>

#define BCM2708_PERI_BASE 0x20000000
#define GPIO_BASE (BCM2708_PERI_BASE + 0x200000) /* GPIO controller */
#define PAGE_SIZE (4*1024)
#define BLOCK_SIZE (4*1024)

int mem_fd;
void *gpio_map;
volatile unsigned *gpio;
void setup_io();

// GPIO setup macros. Always use INP_GPIO(x) before using OUT_GPIO(x) or SET_GPIO_ALT(x,y)
#define INP_GPIO(g) *(gpio+((g)/10)) &= ~(7<<(((g)%10)*3))
#define OUT_GPIO(g) *(gpio+((g)/10)) |= (1<<(((g)%10)*3))
#define SET_GPIO_ALT(g,a) *(gpio+(((g)/10))) |= (((a)<=3?(a)+4:(a)==4?3:2)<<(((g)%10)*3))

#define GPIO_SET *(gpio+7) // sets bits which are 1 ignores bits which are 0
#define GPIO_CLR *(gpio+10) // clears bits which are 1 ignores bits which are 0

int main (int argc, char **argv) {
int opt, flag, n_pin, n_alt;
flag=0;

while ((opt = getopt (argc, argv, "hp:f:")) != -1) {
switch (opt) {
case 'h':
break;
case 'p':
n_pin = atoi(optarg); flag |= 0b0001; break;
case 'f':
n_alt = atoi(optarg); flag |= 0b0010; break;
case '?':
// getopt() prints error messages, so don't need to repeat them here
return 1;
default:
abort ();
}
}

if (flag != 0b0011) {
fprintf (stderr, "Usage:\n$ gpio_alt -p PIN_NUM -f FUNC_NUM\n");
return 1;
}

setup_io(); // Set up gpi pointer for direct register access
INP_GPIO(n_pin); // Always use INP_GPIO(x) before using SET_GPIO_ALT(x,y)
SET_GPIO_ALT(n_pin, n_alt);

printf("Set pin %i to alternative-function %i\n", n_pin, n_alt);

return 0;
}

void setup_io() {
/* open /dev/mem */
if ((mem_fd = open("/dev/mem", O_RDWR|O_SYNC) ) < 0) {
printf("can't open /dev/mem \n");
exit(-1);
}

/* mmap GPIO */
gpio_map = mmap(
NULL, //Any adddress in our space will do
BLOCK_SIZE, //Map length
PROT_READ|PROT_WRITE,// Enable reading & writting to mapped memory
MAP_SHARED, //Shared with other processes
mem_fd, //File to map
GPIO_BASE //Offset to GPIO peripheral
);

close(mem_fd); //No need to keep mem_fd open after mmap

if (gpio_map == MAP_FAILED) {
printf("mmap error %d\n", (int)gpio_map);//errno also set!
exit(-1);
}

// Always use volatile pointer!
gpio = (volatile unsigned *)gpio_map;
}

===================================

Then run following commands to compile and copy it on PATH :
gcc gpio_alt.c -o gpio_alt
sudo chown root:root gpio_alt
sudo chmod u+s gpio_alt
sudo mv gpio_alt /usr/local/bin/

Create a systemd file
/etc/systemd/system/mzdpi.service

=====================================
[Unit]
Description=mzdpi screen blue yellow fix service

[Service]
Type=oneshot
ExecStart=/usr/local/bin/gpio_alt -p 7 -f 2 ; /usr/local/bin/gpio_alt -p 8 -f 2

[Install]
WantedBy=multi-user.target
Alias=mzdpi.service
=====================================

systemctl daemon-reload
systemctl enable mzdpi.service

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Negens: Migrated comment #933