Raspberry Pi GPIO with Lua

libpilwgpio.lua

local ffi = require('ffi')
local lib = ffi.load('libpilwgpio.so') -- https://github.com/besp9510/pi_lw_gpio

-- GPIO operation function prototypes:
ffi.cdef[[
	int gpio_set(int p);
	int gpio_clear(int p);
	int gpio_read_level(int p);
	int gpio_set_mode(int mode, int p);
	int gpio_read_mode(int p);
]]

-- GPIO mode aliases:
local GPIO_INPUT = 0x00
local GPIO_OUTPUT = 0x01

-- Error numbers:
local ENOPIVER = 140 -- Could not get PI board revision

-- Test:

function read_gpio()
	-- Store values and modes:
	local read_gpio_values = {}
	local read_gpio_modes = {}

    -- Read all pins and save to revert later:
	for i = 0, 29 do
		table.insert(read_gpio_values, lib.gpio_read_level(i))
		table.insert(read_gpio_modes, lib.gpio_read_mode(i))
	end
	-- Display the results in a table:
	print('+---+---+----++----+---+---+\n| M | V | GPIO Pin | V | M |\n+---+---+----++----+---+---+')

	for i = 1, 30, 2 do
		print(('| %s | %d | %02d || %02d | %d | %s |'):format(
			read_gpio_modes[i] == GPIO_INPUT and '-' or '+',
			read_gpio_values[i], i, i + 1, read_gpio_values[i + 1],
			read_gpio_modes[i + 1] == GPIO_INPUT and '-' or '+'
		))
	end

	print('+---+---+----++----+---+---+\n| M | V | GPIO Pin | V | M |\n+---+---+----++----+---+---+')
end

-- Simple GPIO test script
function test()
	-- Store values and modes:
	local read_gpio_values = {}
	local read_gpio_modes = {}

    -- Read all pins:
	for i = 0, 29 do
		table.insert(read_gpio_values, lib.gpio_read_level(i))
		table.insert(read_gpio_modes, lib.gpio_read_mode(i))
	end

    -- Begin by reading modes and levels:
    print('Reading all pins')

    -- This will prints results to the screen in a table:
    read_gpio()

    -- Next by setting all to output:
    print('All pins to output')

    -- Set all pins to output:
	for i = 0, 29 do
        lib.gpio_set_mode(GPIO_OUTPUT, i)
	end

    read_gpio()

    -- Then set (V = 1):
    print('All pins set')

    -- Set all pins:
	for i = 0, 29 do
		lib.gpio_set(i)
	end

    read_gpio()

    -- Next clear (V = 0):
	print('All pins cleared')

    -- Clear all pins:
	for i = 0, 29 do
		lib.gpio_clear(i)
	end

    read_gpio()

    -- Lastly, set to input:
	print('All pins to input')

    -- Set all pins to input
	for i = 0, 29 do
		lib.gpio_set_mode(GPIO_INPUT, i)
	end

	read_gpio()

    -- Even more lastly, set to modes and levels back to where they were:
    print('All pins reverted')

    -- Set all pins to output
	for i = 0, 29 do
		-- The read modes will map directly to GPIO_INPUT and GPIO_OUTPUT:
		lib.gpio_set_mode(read_gpio_modes[i + 1], i)

        -- Set or clear depending on last read value:
		lib[read_gpio_values[i + 1] == 1 and 'gpio_set' or 'gpio_clear'](i)
	end

	read_gpio()
end

test()