pi-sense-hat

An event-based wrapper around the python sense-hat library, based on the node-red-node-pi-sense-hat library.

Usage

Examples

Example code is provided in plain javascript and typescript, in the ./examples folder.

Events

A SenseHat instance generates readings from the various sensors on the Sense HAT, grouped into three different event types:

• motion
• environment
• joystick

Motion events

Motion events include readings from the accelerometer, gyroscope and magnetometer, as well as the current compass heading. They are sent at a rate of approximately 10 per second. The motion event passes an object with the following values:

• acceleration.x/y/z : the acceleration intensity in Gs
• gyroscope.x/y/z : the rotational intensity in radians/s
• orientation.roll/pitch/yaw : the angle of the axis in degrees
• compass : the direction of North in degrees

Environment events

Environment events include readings from the temperature, humidity and pressure sensors. They are sent at a rate of approximately 1 per second. The environment event passes an object with the following values:

• temperature : degrees Celsius
• humidity : percentage of relative humidity
• pressure : Millibars

Joystick events

Joystick events are sent when the Sense HAT joystick is interacted with. The joystick event passes object with the following values:

• key : one of UP, DOWN, LEFT, RIGHT, ENTER
• state : the state of the key:
  • 0 : the key has been released
  • 1 : the key has been pressed
  • 2 : the key is being held down

Output Methods

These methods send commands to the 8x8 LED display on the Sense HAT.

Set the colour of individual pixels

setPixelColour(x, y, colour, x2, y2, colour...)

x and y must either be a value from 0 to 7, a * to indicate the entire row or column, or a range such as 3-6.

colour must be one of:

• the well-known HTML colour names - eg red or aquamarine,
• the CheerLights colour names,
• a HEX colour value - eg #aa9900
• an RGB triple - 190,255,0
• or simply off

To set the entire screen to red:

let senseHat = require('../dist/sense-hat').create();
senseHat.setPixelColour('*','*','red')

To set the four corners of the display to red, green (#00ff00), yellow and blue (0,0,255):

let senseHat = require('../dist/sense-hat').create();
senseHat.setPixelColour(0,0,'red',0,7,'#00ff00',7,7,'yellow',7,0,0,0,255)

To set a 3-pixel wide column to purple:

let senseHat = require('../dist/sense-hat').create();
senseHat.setPixelColour('4-6','*','purple')

Rotate the screen

rotate(angle:0|90|180|270)

angle must be 0, 90, 180 or 270.

Example:

let senseHat = require('../dist/sense-hat').create();
senseHat.rotate(180);

Flip the screen

flip(horizontal=true)

To flip on the horizontal or vertical axis respectively.

Example:

let senseHat = require('../dist/sense-hat').create();
senseHat.flip(true); 

Display a message

displayMessage(text:string, colour:string="white", background:string="off", speed:number=3)

If the text is a single character, it will be displayed without scrolling. To scroll a single character, append a blank space after it - "A ".

The following message properties can be used to customise the appearance:

• text - the text to be displayed. If the text is a single character, it will be displayed without scrolling. To scroll a single character, append a blank space after it - "A ".
• colour - the colour of the text, default: white
• background - the colour of the background, default: off
• speed - the scroll speed. A value in the range 1 (slower) to 5 (faster), default: 3

Example:

let senseHat = require('../dist/sense-hat').create();
senseHat.displayMessage("Hello world", "blue", "green", 4);

Set the screen brightness

brightness(high=true)

`To flip on the horizontal or vertical axis respectively.

Example:

let senseHat = require('../dist/sense-hat').create();
senseHat.brightness(true); 

Credits

The library was based on the node-red-pi library under the terms of the Apache 2.0 license agreement:

Directly copied:

• sensehat.py
• scripts/checklib.sh

Adapted:

• readme.md
• src/sense-hat.ts (adpated from sensehat.js)
• colours.ts (adapted from colours.js)