mmm-usonic

A high performance, memory mapped, Node.js API for the HC-SR04 ultrasonic sensor connected to a Raspberry Pi. It's the updated version of clebert's r-pi-usonic API.

Getting Started

Installation

npm install mmm-usonic --save

Integration

var usonic = require('mmm-usonic');

API

usonic.init(callback)

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

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

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

usonic.createSensor(echoPin, triggerPin, [timeout])

Creates a new ultrasonic sensor function and returns it. The measurement timeout has a default value of 750 µs.

var sensor = usonic.createSensor(24, 23, 450);

sensor()

Returns the distance in cm if no measurement timeout occurs, and -1 otherwise.

var distance = sensor();

Example

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

sudo node examples/surveyor.js

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

Running Tests

To run the test suite first install the development dependencies:

npm install

then run the tests:

npm test

smart-facility/mmm-usonic