node-red-node-pi-sense-hat
A Node-RED node to interact with a Raspberry Pi Sense HAT.
Pre-requisites
The Sense HAT python drivers need to be installed manually:
sudo apt-get update
sudo apt-get install sense-hat
sudo pip-3.2 install pillow
See the driver documentation for more information.
Install
Run the following command in your Node-RED user directory (typically ~/.node-red
):
npm install node-red-node-pi-sense-hat
Usage
Input Node
This node sends readings from the various sensors on the Sense HAT, grouped into three sets; motion events, environment events and joystick events.
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 topic
is set to motion
and the payload
is 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 topic
is set to environment
and the payload
is 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
topic
is set to joystick
and the payload
is an object with the following values:
-
key
: one ofUP
,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 Node
This node sends commands to the 8x8 LED display on the Sense HAT.
Commands are sent to the node in msg.payload
. Multiple commands can
be sent in a single message by separating them with newline (\n) characters.
You must use a function node or a change node (jsonata expression) when
using the newline (\n) character to create a payload containing multiple commands.
Set the colour of individual pixels
Format: <x>,<y>,<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
oraquamarine
, - 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: *,*,red
To set the four corners of the display to red, green (#00ff00), yellow and blue (0,0,255):
0,0,red,0,7,#00ff00,7,7,yellow,7,0,0,0,255
To set a 3-pixel wide column to purple: 4-6,*,purple
Rotate the screen
Format: R<angle>
angle
must be 0, 90, 180 or 270.
Example: R180
Flip the screen
Format: F<axis>
axis
must be either H
or V
to flip on the horizontal or vertical axis respectively.
Example: FV
Scroll a message
If msg.payload
is not recognised as any of the above commands, it is treated
as a text message to be scrolled across the screen.
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:
-
msg.color
- the colour of the text, default:white
-
msg.background
- the colour of the background, default:off
-
msg.speed
- the scroll speed. A value in the range 1 (slower) to 5 (faster), default:3
Set the screen brightness
Format: D<level>
level
must be 0 (low) or 1 (high).
Example: D1