GPIO Mock



A framework to mock GPIO by redirecting calls to /sys/class/gpio/ to ./sys/class/gpio/

This framework does not provide any simulated hardware, with the exception of DS18B20 digital thermomters which can be
simulated in a number of ways.

GPIO Mock redirects any fs function call concerning paths starting with '/sys/class/gpio' to (by default)
'./sys/class/gpio'. This means that tests that either do not require hardware, or tests that can function with
simulated hardware can function without changes to the code.

Documentation

Version 1.2.0

#### Older versions
* Version 1.1.2
* Version 1.1.1
* Version 1.1.0
* Version 1.0.1
* Version 1.0.0

Some examples

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####Test
``
let gpioMock = require('gpio-mock');
let fs = require('fs');

gpioMock.start(function(err) {
fs.writeFile('/sys/class/gpio/export', '1', function(err) {
if (!err) {
// GPIO 1 is exported.
fs.writeFile('/sys/class/gpio/gpio1/direction', 'out', function(err) {
if (!err) {
// GPIO 1 is set to out
fs.writeFile('/sys/class/gpio/gpio1/value', 1, function(err) {
// GPIO 1 is set to high
}
}
});
}
});

// Reset changes to fs when done
gpioMock.stop();
});
`

#### Simulated hardware

`
let fs = require('fs');

// Simulated LED
function ledSwitch() {
setTimeout(function() {
fs.readFile('./sys/gpio/gpio1/value', 'utf8', function(err, fd) {
if (!err && fd === '1') {
console.log('LED is on!');
}
});
ledSwitch();
}, 200)
}
`

The simulated LED above could just as well be an IR LED, with a simulated IR receiver writing '1' to
./sys/class/gpio/gpio2/value when GPIO1 is '1', and writing '2' when GPIO1 is '0';




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####Test
`
let gpioMock = require('gpio-mock');
let gpio = require('mc-gpio');

gpioMock.start(function(err) {
gpio.openPinOut(1, function(err, data) {
if (!err) {
// GPIO1 is open and set to out
gpio.write(1, '1', function(err, data) {
if (!err) {
// GPIO1 is set to high
}
}
}
});

// Reset changes to fs when done
gpioMock.stop();
});
`

#### Simulated hardware

`
let fs = require('fs');

// Simulated LED
function ledSwitch() {
setTimeout(function() {
fs.readFile('./sys/gpio/gpio1/value', 'utf8', function(err, fd) {
if (!err && fd === '1') {
console.log('LED is on!');
}
});
ledSwitch();
}, 200)
}
`

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`
let gpioMock = require('gpio-mock');
let ds18b20 = require('mc-tempsensor');

// Hardware definition for DS18B20;
let f = {
"behavior": "function",
"temperature": function() {
return Math.random() * 100000;
}
};

gpioMock.start(function(err) {
gpioMock.addMockHardwareModule('ds18b20', 'ds18b20.js', function(err) {
if (!err) {
gpioMock.addMockHardware('ds18b20', '28-800000263717', f, function(err) {
if (!err) {
tempsensor.init('28-800000263717');

tempSensor.readAndParse(function(err, data) {
if (err) {
// Handle error
} else {
console.log('Temperature is ' + data[0].temperature.celcius + ' C');
}
});
} else {
callback(err);
}
});
} else {
callback(err);
}
});
});
`

For some more concrete examples, take a look at Mash Control

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If the basic GPIO mocking is not enough, for example when using something that behaves similar to the DS18B20 digital
thermometer, you can write a Mock Hardware module and add it as the above example shows.

Have a look att ds18b20.js for a functioning implementation and mockHardwareExample.js for a skeleton. What is most
important are the functions and variables exposed by the module. Below is the module.exports taken from
mockHardwareExample.js

`
module.exports = {
functionHardware: functionHardware,
staticHardware: staticHardware,
stop: stop,
add: add,
set: set,
remove: remove,
sysPath: sysPath,
mockPath: mockPath
};
`

This is the minimum required by GPIO Mock to work.

* functionHardware = function() {};
* Called every 500 ms when updating mocked hardware. This is used to update mocked hardware according to a function
* staticHardware = function() {};
* Called every 500 ms when updating mocked hardware. This is used to reset mocked hardware to a set value, in case any
external process has manipulated it.
* stop = function() {};
* Called when gpio-mock is stopped. This should stop everything in the mocked hardware module and clear all mocked
hardware.
* add = function(id, hardwareDefinition, callback) {};
* Called to add a new instance of the mocked hardware. This function should not replace already existing mocked
hardware.
* id a unique id for the mocked hardware instance
* hardwareDefinition an object representing the hardware instance
* callback callback function
* set = function(id, hardwareDefinition, callback) {};
* Called to replace an instance of the mocked hardware.
* id id for the mocked hardware instance to update the definition of
* hardwareDefinition an object representing the hardware instance
* callback callback function
* remove = function(id, callback) {};
* Called to remove an instance of the mocked hardware.
* id id of the mocked hardware instance to remove
* callback callback function
* sysPath
* This is a constant string representation of any file system representation if the mocked hardware, it should point
to the 'root' directory of the hardware in the file system.
* mockPath`
* This is a variable string representation of the mocked file system representation. It can be given a default value,
however gpio-mock will overwrite it.