RE: C++ gpio library for Raspberry Pi - Pt 2: Plug In drivers for direct register GPIO, or file system based GPIO

DAB — Sat, 06 Jan 2024 20:16:08 GMT

Great update Jan.

RE: C++ gpio library for Raspberry Pi - Pt 2: Plug In drivers for direct register GPIO, or file system based GPIO

Jan Cumps — Sat, 06 Jan 2024 18:34:57 GMT

This little test program lets you set or read a pin:

[embed:dc8ab71f-3b98-42d9-b0f6-e21e02a0f8e2:56d2c67d-37d8-49f8-b8c8-3206ccf1ccac:type=c_cpp&text=%2F%2F%20uncomment%20the%20gpio%20handler%20that%20you%20want%20to%20use%0D%0A%2F%2F%23define%20DPGIO_SYSFS_FILEHANDLER%0D%0A%23define%20DPGIO_SYSFS_STREAM%0D%0A%2F%2F%23define%20DPGIO_MEMMAP%0D%0A%0D%0A%23include%20%22pin.h%22%0D%0A%0D%0A%23if%20defined%20DPGIO_SYSFS_FILEHANDLER%0D%0A%23include%20%3Csysfsdevice_filehandler.h%3E%0D%0Atypedef%20dgpio%3A%3Apin%3Cdgpio%3A%3Asysfsdevice_filehandler%3E%20pin%3B%0D%0A%23elif%20defined%20DPGIO_SYSFS_STREAM%0D%0A%23include%20%22sysfsdevice_stream.h%22%0D%0Atypedef%20dgpio%3A%3Apin%3Cdgpio%3A%3Asysfsdevice_stream%3E%20pin%3B%0D%0A%23elif%20defined%20DPGIO_MEMMAP%0D%0A%23include%20%22memmapdevice.h%22%0D%0Atypedef%20dgpio%3A%3Apin%3Cdgpio%3A%3Amemmapdevice%3E%20pin%3B%0D%0A%23endif%0D%0A%0D%0A%23include%20%3Cstdlib.h%3E%20%20%20%20%20%2F%2A%20atoi%20%2A%2F%0D%0Aint%20main%28int%20argc%2C%20char%20%2Aconst%20%2Aargv%29%20%7B%0D%0A%20%20%20%20if%20%28argc%20%3C%202%29%20%7B%0D%0A%09%09return%20-1%3B%0D%0A%20%20%20%20%7D%0D%0A%0D%0A%20%20%20%20int%20retval%20%3D%200%3B%0D%0A%0D%0A%20%20%20%20unsigned%20int%20gpio%20%3D%20atoi%28argv%5B1%5D%29%3B%0D%0A%20%20%20%20pin%3A%3Adir%20dir%20%3D%20pin%3A%3Adir%3A%3Ain%3B%0D%0A%20%20%20%20pin%3A%3Astatus%20status%20%3D%20pin%3A%3Astatus%3A%3Aoff%3B%0D%0A%0D%0A%20%20%20%20if%20%28argc%20%3D%3D%203%29%20%7B%20%2F%2F%20out%0D%0A%20%20%20%20%09dir%20%3D%20pin%3A%3Adir%3A%3Aout%3B%0D%0A%20%20%20%20%09if%20%28atoi%28argv%5B2%5D%29%20%3D%3D%201%29%20%7B%0D%0A%20%20%20%20%09%09status%20%3D%20pin%3A%3Astatus%3A%3Aon%3B%0D%0A%20%20%20%20%09%7D%0D%0A%20%20%20%20%7D%0D%0A%0D%0A%09pin%20p%20%3D%20pin%28gpio%29%3B%0D%0A%09p.init%28dir%29%3B%0D%0A%0D%0A%09if%20%28dir%20%3D%3D%20pin%3A%3Adir%3A%3Ain%29%20%7B%0D%0A%09%09pin%3A%3Astatus%20s%20%3D%20p.get%28%29%3B%0D%0A%09%09retval%20%3D%20s%20%3D%3D%20pin%3A%3Astatus%3A%3Aon%20%3F%201%20%3A%200%3B%0D%0A%09%7D%20else%20%7B%0D%0A%09%09p.set%28status%29%3B%0D%0A%09%7D%0D%0A%0D%0A%09p.deinit%28%29%3B%0D%0A%09return%20retval%3B%0D%0A%7D%0D%0A%0D%0A]

to read a pin:

./device_gpio 21

the return value holds the state, and can be retrieved:

echo $?

to set a pin high:

./device_gpio 21 1

to set a pin low:

./device_gpio 21 0

Test with a real GPIO pin please [emoticon:44a8a53ad3364ea78a16c5a3229f75bb] - the program will happily set any Broadcom BCMxxx CPU pin below 30, or change its function to GPIO.

No root needed, but you have to be in the gpio group.

RE: C++ gpio library for Raspberry Pi - Pt 2: Plug In drivers for direct register GPIO, or file system based GPIO

Jan Cumps — Fri, 05 Jan 2024 14:31:52 GMT

fun fact: you can use one driver for pin A, and another for pin B. The only thing you have to do is make the two typedefs unique. Example:

[embed:dc8ab71f-3b98-42d9-b0f6-e21e02a0f8e2:9ed23e88-45d5-4268-b0b8-5065d3475fb7:type=c_cpp&text=%23include%20%22pin.h%22%0A%0A%23include%20%22sysfsdevice_stream.h%22%0Atypedef%20dgpio%3A%3Apin%3Cdgpio%3A%3Asysfsdevice_stream%3E%20fs_pin%3B%0A%0A%23include%20%22memmapdevice.h%22%0Atypedef%20dgpio%3A%3Apin%3Cdgpio%3A%3Amemmapdevice%3E%20reg_pin%3B%0A%0A%2F%2F%20...%0A%0A%09fs_pin%20p21%20%3D%20fs_pin%2821%29%3B%0A%09reg_pin%20p23%20%3D%20reg_pin%2823%29%3B%0A%0A%2F%2F%20...]

Is that useful? Who knows [emoticon:c4563cd7d5574777a71c318021cbbcc8]

RE: C++ gpio library for Raspberry Pi - Pt 2: Plug In drivers for direct register GPIO, or file system based GPIO

BigG — Fri, 05 Jan 2024 12:25:54 GMT

Not sure if helpful, but I know Adafruit's Circuit Python library for the Raspberry Pi uses libgpiod. https://github.com/adafruit/Adafruit_Blinka