accelerometer.md

Accelerometer

Use the accelerometer module to simplify the use of the accelerometer sensors as controls on mobile devices. The module can calibrate the accelerometer data based on the current device orientation (along all axis). The module stores multiple samples and provides an average value to reduce the jitter typically seen in accelerometer sensors.

Usage

You can use the accelerometer either through the accelerometer.lua module or the accelerometer.script script.

Accelerometer module

Require the module, create an instance or use the global singleton, calibrate, feed it accelerometer samples and read adjusted values:

local acc = require "in.accelerometer"

function init(self)
	-- create accelerometer instance with 20 samples
	self.acc = acc.create(20)
	-- calibrate it based on current device orientation
	self.acc.calibrate()
end

function update(self, dt)
	-- read adjusted (taking into account calibration) accelerometer value
	local adjusted = self.acc.adjusted()
	print(adjusted)
end

function on_input(self, action_id, action)
	-- feed it calibration data
	self.acc.on_input(action)
end

Dynamic orientation

The module can take into account dynamic screen orientation and adjust the returned sensor values to accommodate for a change in screen orientation. You can notify the module of an orientation change using the on_window_resized() function:

local acc = require "in.accelerometer"

function init(self)
	window.set_listener(function(self, event, data)
		if event == window.WINDOW_EVENT_RESIZED then
			acc.on_window_resized(data.width, data.height)
		end
	end)
end

Accelerometer script

Attach the accelerometer.script to a game object, calibrate, feed it accelerometer samples and read adjusted values via messages:

function init(self)
	msg.post("#accelerometer", "calibrate")
end

function on_message(self, message_id, message, sender)
	if message_id == hash("accelerometer") then
		print(message.x, message.y, message.z)
	end
end

Script properties

The script has the following properties:

• samplecount - (number) The number of sample to keep in memory and calculate an average for

Messages

The script will generate messages to game object it is attached to:

• accelerometer - Accelerometer data received from the script

The script will accept the following messages:

• calibrate - Trigger a calibration of the accelerometer
• on_window_resize - Notify the script of a window resize (expects message to contain width and height)