local p = require "posix"

local dev = arg[1] or "/dev/ttyUSB0"

-- Open serial port and do settings

local fds, err = p.open(dev, p.O_RDWR + p.O_NONBLOCK);

if not fds then

	print("Could not open serial port " .. dev .. ":", err)

	os.exit(1)

end

p.tcsetattr(fds, 0, {

	cflag = p.B115200 + p.CS8 + p.CLOCAL + p.CREAD,

	iflag = p.IGNPAR,

	oflag = p.OPOST,

	cc = {

		[p.VTIME] = 0,

		[p.VMIN] = 1

	}

})

-- Set stdin to non canonical mode. Save current settings

local save = p.tcgetattr(0)

p.tcsetattr(0, 0, {

	cc = {

		[p.VTIME] = 0,

		[p.VMIN] = 1

	}

})

-- Loop, reading and writing between ports. ^C stops

local set = {

	[0] = { events = { IN = true } },

	[fds] = { events = { IN = true } },

}

p.write(1, "Starting terminal, hit ^C to exit\r\n")

local function exit(msg)

	p.tcsetattr(0, 0, save)

	print("\n")

	print(msg)

	os.exit(0)

end

while true do

	local r = p.poll(set, -1)

	for fd, d in pairs(set) do

		if d.revents and d.revents.IN then

			if fd == 0 then

				local d, err = p.read(0, 1024)

				if not d then exit(err) end

				if d == string.char(3) then exit("Bye") end

				local ok, err = p.write(fds, d)

				if not ok then exit(err) end

			end

			if fd == fds then

				local d, err = p.read(fds, 1024)

				if not d then exit(err) end

				local ok, err = p.write(1, d)

				if not ok then exit(err) end

			end

		end

	end

end