PINE64
OpenBSD: GPIO with the I2C device PCF8574(A) - Printable Version

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+--- Thread: OpenBSD: GPIO with the I2C device PCF8574(A) (/showthread.php?tid=6377)

OpenBSD: GPIO with the I2C device PCF8574(A) - krjdev - 08-09-2018

Currently the ROCK64 GPIO cannot used in userland. (I currently working on it.)

So I have written a driver for the good old PCF8574 from NXP.
You can find the driver on my Github page:

Additional drivers for OpenBSD

To use the PCF8574, add this to the device trees (Example):

Code:
/dts-v1/; /include/ "rk3328-rock64.dts" &i2c0 {    status = "okay";    pcf8574: gpio@20 {        compatible = "nxp,pcf8574";        status = "okay";        reg = <0x20>;        #gpio-cells = <2>;        gpio-controller;    }; };

Configuration of the Kernel (add the following):

Code:
pcfgpio*    at iic? gpio*       at pcfgpio?

Compile the kernel.

dmesg output from my driver:

Code:
pcfgpio0 at iic0 addr 0x20 gpio0 at pcfgpio0: 8 pins



Use the driver with gpioctl:

Code:
$ gpioctl /dev/gpio0 0 on
Turns pin 0 to on.



Use the driver with ioctls (simple running light example):

Code:
#include <unistd.h> #include <fcntl.h> #include <stdio.h> #include <errno.h> #include <string.h> #include <sys/types.h> #include <sys/gpio.h> #include <sys/ioctl.h> int main(int argc, char *argv[]) {    int i, fd;    int ret;    struct gpio_info ginfo;    struct gpio_pin_op gop;        if (argc < 2) {        printf("usage: gpio [DEV]\n");        return 1;    }    fd = open(argv[1], O_RDWR);    if (fd == -1) {        printf("error: couldn't open file (%s)\n", strerror(errno));        return 1;    }    ret = ioctl(fd, GPIOINFO, &ginfo);    if (ret == -1) {        printf("error: ioctl GPIOINFO failed (%s)\n", strerror(errno));        close(fd);        return 1;    }    printf("gpio: Number of pins: %d\n", ginfo.gpio_npins);    while (1) {        for (i = 0; i < ginfo.gpio_npins; i++) {            gop.gp_pin = i;            gop.gp_value = GPIO_PIN_HIGH;            ret = ioctl(fd, GPIOPINWRITE, &gop);            if (ret == -1) {                printf("error: ioctl GPIOPINWRITE failed (%s)\n", strerror(errno));                close(fd);                return 1;            }            sleep(1);            gop.gp_value = GPIO_PIN_LOW;            ret = ioctl(fd, GPIOPINWRITE, &gop);            if (ret == -1) {                printf("error: ioctl GPIOPINWRITE failed (%s)\n", strerror(errno));                close(fd);                return 1;            }        }    }    close(fd);    return 0; }