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r-pi-gpio

A high performance, memory mapped, Node.js API for GPIO on the Raspberry Pi.

Getting Started

Installation

npm install r-pi-gpio --save

Integration

var gpio = require('r-pi-gpio');

API

gpio.init(callback)

Creates the memory mapping with a device-specific memory offset.

You must call this function only once and before any other function.

gpio.init(function (error) {
    if (error) {
        ...
    } else {
        ...
    }
});

gpio.createInput(pin)

Creates a new GPIO input function and returns it.

var input = gpio.createInput(4);

input()

Returns true if the input voltage level is high, and false otherwise.

var level = input();

gpio.createOutput(pin)

Creates a new GPIO output function and returns it.

var output = gpio.createOutput(4);

output(level)

Sets the output voltage level to high or low.

output(true);
output(false);

Example

This example needs access to the physical memory, so it must run as root.

sudo node examples/onoff.js

A quick word about the electronics involved. LEDs are Light Emitting Diodes and the diode part is important for us – they only pass electricity one way, so we need to make sure we put them in the right way round. They have a long leg and a slightly shorter leg. The long leg goes to the plus side and the shorter leg to the negative (or 0v) side. If we’re cut the legs short (as I have done here), then another way is to look at the side of the LED – there will be a flat section. Think of the flat as a minus sign and connect that to the 0v side of the circuit.

If we allow too much current through the LED, it will burn very bright for a very short period of time before it burns out, so we need a resistor to limit the current. Calculating the resistor value is not difficult but for now, just use anything from 270Ω to 330Ω. Anything higher will make the LED dimmer.

-- GPIO Examples - A single LED

Raspberry Pi GPIO Pin Layout

Raspberry Pi Model A/B (Rev 1.0)

Assignment	Pin	Pin	Assignment
3.3V	1	2	5V
GPIO 0 (SDA0)	3	4	5V
GPIO 1 (SCL0)	5	6	GROUND
GPIO 4	7	8	GPIO 14 (TXD0)
GROUND	9	10	GPIO 15 (RXD0)
GPIO 17	11	12	GPIO 18
GPIO 21	13	14	GROUND
GPIO 22	15	16	GPIO 23
3.3V	17	18	GPIO 24
GPIO 10 (SPI_MOSI)	19	20	GROUND
GPIO 9 (SPI_MISO)	21	22	GPIO 25
GPIO 11 (SPI_SCLK)	23	24	GPIO 8 (SPI_CE0_N)
GROUND	25	26	GPIO 7 (SPI_CE1_N)

Raspberry Pi Model A/B (Rev 2.0)

Assignment	Pin	Pin	Assignment
3.3V	1	2	5V
GPIO 2 (SDA1)	3	4	5V
GPIO 3 (SCL1)	5	6	GROUND
GPIO 4	7	8	GPIO 14 (TXD0)
GROUND	9	10	GPIO 15 (RXD0)
GPIO 17	11	12	GPIO 18
GPIO 27	13	14	GROUND
GPIO 22	15	16	GPIO 23
3.3V	17	18	GPIO 24
GPIO 10 (SPI_MOSI)	19	20	GROUND
GPIO 9 (SPI_MISO)	21	22	GPIO 25
GPIO 11 (SPI_SCLK)	23	24	GPIO 8 (SPI_CE0_N)
GROUND	25	26	GPIO 7 (SPI_CE1_N)

Raspberry Pi Model B+ / Raspberry Pi 2 Model B

Assignment	Pin	Pin	Assignment
3.3V	1	2	5V
GPIO 2 (SDA1)	3	4	5V
GPIO 3 (SCL1)	5	6	GROUND
GPIO 4	7	8	GPIO 14 (TXD0)
GROUND	9	10	GPIO 15 (RXD0)
GPIO 17	11	12	GPIO 18
GPIO 27	13	14	GROUND
GPIO 22	15	16	GPIO 23
3.3V	17	18	GPIO 24
GPIO 10 (SPI_MOSI)	19	20	GROUND
GPIO 9 (SPI_MISO)	21	22	GPIO 25
GPIO 11 (SPI_SCLK)	23	24	GPIO 8 (SPI_CE0_N)
GROUND	25	26	GPIO 7 (SPI_CE1_N)
ID_SD	27	28	ID_SC
GPIO 5	29	30	GROUND
GPIO 6	31	32	GPIO 12
GPIO 13	33	34	GROUND
GPIO 19	35	36	GPIO 16
GPIO 26	37	38	GPIO 20
GROUND	39	40	GPIO 21

Related Links

• RPi Low-level Peripherals
• BCM2835 ARM Peripherals
• GPIO Examples - A single LED
• Standard Resistor Values
• Pull-up and Pull-down Resistors

Running Tests

To run the test suite first install the development dependencies:

npm install

then run the tests:

npm test