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Previous: Smart Plug Prototype 0.4
Here we finally do the real thing. We wire up a GPIO pin and a ground pin to a commercial relay1.
Using the control protocol written for the Beaglebone’s onboard LEDs (and pointing the code to a different pin), we can now fully control a lamp remotely. We now have a usable prototype; however, this is only a demo of controlled, high-voltage switching. There are a couple more steps before we have a full proof-of-concept. The next is controlling over the home network, not over a USB network.
var b = require('bonescript');
var net = require('net');
// controlling different GPIO pin for relay
var LEDS = ['P8_7'];
var open_sockets = [];
var state = b.HIGH;
function setState(new_state) {
if (new_state !== state) {
state = new_state;
LEDS.forEach(function (LED) {
b.pinMode(LED, b.OUTPUT);
b.digitalWrite(LED, state);
});
writeStateAllSockets();
return true;
} else {
return false;
}
}
setState(b.LOW);
function writeState(socket) {
socket.write(state + '\n');
}
function writeStateAllSockets() {
open_sockets.forEach(writeState);
}
setInterval(writeStateAllSockets, 10000);
var server = net.createServer(function (socket) {
writeState(socket);
open_sockets.push(socket);
socket.on('end', function () {
open_sockets = open_sockets.filter(function (remove_socket) {
return remove_socket !== socket;
});
});
socket.on('error', function (error) {
console.log('error', error);
});
socket.on('data', function (data) {
var command_character = data.slice(0, 1);
var ascii_signal = parseInt(command_character.toString('ascii'), 10);
var state_changed = false;
if (ascii_signal === 1) {
state_changed = setState(b.HIGH);
} else if (ascii_signal === 0) {
state_changed = setState(b.LOW);
} else {
socket.write('!\n');
return;
}
if (!state_changed) {
writeState(socket);
}
});
});
server.listen(9999, function () {
console.log('Ready for commands');
});
Next: Smart Plug Prototype 0.6