gpio-erlang

Goals

• Provide GPIO controller from Erlang/OTP Application.

CAUTION

Now, gpio-erlang supported RaspberryPi only, I will support other devices, that running general GNU/Linux operating system.

Getting Started

Log in your RaspberryPi and fetch the latest version of gpio-erlang using git.

$ git clone https://github.com/hiroeorz/gpio-erlang.git
$ cd gpio-erlang
$ make

Or add "deps" line to your app's rebar.conf.

{gpio, ".*", {git, "https://github.com/hiroeorz/gpio-erlang.git",
   {branch, "master"}}},

and get deps

$ ./rebar get-deps

Running

check default setting of gpio.

In default setting, gpio 25,27 is output pin, other is input pin.

You can change pin setting by modifing above file, if you need.

Start application.

You must run gpio-erlang as root. Because gpio-erlang access to /dev/mem. /dev/mem is allowed writable access from root only.

$ sudo ./start-dev

---

or start erlang mode as root

$ sudo erl -pa ebin deps/*/ebin -boot start_sasl -sname gpio -setcookie gpio

and start gpio in erl shell.

1> application:start(gpio).

---

General Purpose I/O

Read gpio value

1> gpio_pin:read(18).
0

Write value to gpio

1> gpio_pin:write(25, 1).
ok
3> gpio_pin:write(25, 0).
ok

Change Pin mode

1> gpio_pin:set_pin_mode(18, out).
ok
2> gpio_pin:set_pin_mode(25, in).
ok

Pullup or pulldown

1> gpio_pin:pullup(18).
ok
2> gpio_pin:pulldown(18).
ok
3> gpio_pin:pullnone(18).
ok

Set interrupt

1> gpio_pin:set_int(18, rising).
ok
2> gpio_pin:set_int(18, falling).
ok
3> gpio_pin:set_int(18, both).
ok
4> gpio_pin:set_int(18, none).
ok

Get active low

1> gpio_pin:get_active_low(4).
0

Set active low

1> gpio_pin:set_active_low(25, 1).

example:

1> gpio_pin:write(25, 1).
ok
2> gpio_pin:read(25).
1
3> gpio_pin:set_active_low(25, 1).
ok
2> gpio_pin:read(25).
0

Add event handler of gpio pin

1> gpio_pin_event:add_event_handler(sample_module, []).
ok

• First argument is module name.
• Second argument is arguments of sample_module:init/1.

The sample_module is event handler befavior of gen_event. If gpio18 set interrupt rising and pin status changed 0 to 1 , called event handler.

This is sample event handler. gpio_pin_event_logger.erl