Node.js Raspberry Pi GPIO - LED en drukknop
Gebruik beide invoer en uitvoer
In die vorige hoofstuk het ons geleer hoe om 'n Raspberry Pi en sy GPIO te gebruik om 'n LED te laat flikker.
Daarvoor het ons 'n GPIO-pen as "Uitvoer" gebruik.
In hierdie hoofstuk sal ons 'n ander GPIO-pen as "Invoer" gebruik.
In plaas daarvan om vir 5 sekondes te flikker, wil ons hê die LED moet brand wanneer jy 'n knoppie druk wat aan die broodbord gekoppel is.
Wat het ons nodig?
In hierdie hoofstuk sal ons 'n eenvoudige voorbeeld skep waar ons 'n LED-lig met 'n drukknoppie beheer.
Hiervoor benodig jy:
- 'n Raspberry Pi met Raspian, internet, SSH, met Node.js geïnstalleer
- Die aanskakelmodule vir Node.js
- 1 x Broodbord
- 1 x 68 Ohm weerstand
- 1 x 1k Ohm weerstand
- 1 x LED deur gat
- 1 x Drukknop
- 4 x vroulike tot manlike jumper drade
- 1 x Mannetjie tot Mannetjie jumper drade
Klik op die skakels in die lys hierbo vir beskrywings van die verskillende komponente.
Let wel: Die weerstand wat u benodig, kan verskil van wat ons gebruik, afhangende van die tipe LED wat u gebruik. Die meeste klein LED's benodig net 'n klein weerstand, ongeveer 200-500 ohm. Dit is oor die algemeen nie krities watter presiese waarde jy gebruik nie, maar hoe kleiner die waarde van die weerstand, hoe helderder sal die LED skyn.
In hierdie hoofstuk gaan ons voortbou op die stroombaan wat ons in vorige hoofstuk gebou het, sodat jy sommige van die dele in die lys hierbo sal herken.
Die bou van die kring
Nou is dit tyd om die kring op ons Broodbord te bou. Ons sal die stroombaan wat ons in die laaste hoofstuk geskep het as 'n beginpunt gebruik.
As jy nuut is met elektronika, beveel ons aan dat jy die krag vir die Raspberry Pi afskakel. En gebruik 'n anti-statiese mat of 'n grondband om te verhoed dat dit beskadig word.
Skakel die Raspberry Pi behoorlik af met die opdrag:
pi@w3demopi:~ $ sudo shutdown -h now
Nadat die LED's op die Raspberry Pi ophou flikker, trek dan die kragprop uit die Raspberry Pi (of draai die kragstrook waaraan dit gekoppel is) uit.
Deur net die prop te trek sonder om behoorlik af te skakel, kan die geheuekaart beskadig word.
Kyk na die bostaande illustrasie van die stroombaan.
- Starting with the circuit we created in the last chapter:
On the Raspberry Pi, connect the female leg of a jumper wire to a 5V power pin. In our example we used Physical Pin 2 (5V, row 1, right column) - On the Breadboard, connect the male leg of the jumper wire connected to the 5V power, to the Power Bus on the right side. That entire column of your breadboard is connected, so it doesn't matter which row. In our example we attached it to row 1
- On the Breadboard, connect the push button so that it fits across the Trench. In our example it connects to rows 13 and 15, columns E and F
- On the Breadboard, connect one leg of the 1k ohm resistor to the Ground Bus column on the right side, and the other leg to the right side Tie-Point row where it connects to one of the right side legs of the push button. In our example we attached one side to Tie-Point row 13, column J, and the other side to the closest Ground Bus hole
- On the Breadboard, connect a male-to-male jumper wire from the right Power Bus, to the right Tie-Point row that connects to the other leg of the push button. In our example we attached one side to Tie-Point row 15, column J, and the other side to the closest Power Bus hole
- On the Raspberry Pi, connect the female leg of a jumper wire to a GPIO pin. In our example we used Physical Pin 11 (GPIO 17, row 6, left column)
- On the Breadboard, connect the male leg of the jumper wire to left Tie-Point row the Push Button leg that is directly across the Ground connection leg. In our example we attached it to row 13, column A
Your circuit should now be complete, and your connections should look pretty similar to the illustration above.
Now it is time to boot up the Raspberry Pi, and write the Node.js script to interact with it.
Raspberry Pi and Node.js LED and Button Script
Go to the "nodetest" directory, and create a new file called "buttonled.js":
pi@w3demopi:~ $ nano buttonled.js
The file is now open and can be edited with the built in Nano Editor.
Write, or paste the following:
buttonled.js
var
Gpio = require('onoff').Gpio; //include onoff to interact with the GPIO
var
LED = new Gpio(4, 'out'); //use GPIO pin 4 as output
var pushButton = new
Gpio(17, 'in', 'both'); //use GPIO pin 17 as input, and 'both' button presses,
and releases should be handled
pushButton.watch(function (err, value) {
//Watch for hardware interrupts on pushButton GPIO, specify callback function
if (err) { //if an error
console.error('There was an
error', err); //output error message to console
return;
}
LED.writeSync(value); //turn LED on or off depending on the button state (0 or
1)
});
function unexportOnClose() { //function to run when exiting program
LED.writeSync(0); // Turn LED off
LED.unexport(); // Unexport LED
GPIO to free resources
pushButton.unexport(); // Unexport Button
GPIO to free resources
};
process.on('SIGINT', unexportOnClose); //function to
run when user closes using ctrl+c
Press "Ctrl+x" to save the code. Confirm with "y", and confirm the name with "Enter".
Run the code:
pi@w3demopi:~ $ node buttonled.js
Now the LED should turn on when you press the button, and turn off when you release it.
End the program with Ctrl+c.