LCD20x4 define & write special character using MQTT

[rwblinn]

Hi,

 

seeking for an example how to define and write a special character to the LCD20x4 bricklet, f.e. arrow up, using the brick-mqtt-proxy?

 

If possible, also how to do the same via javaScript.

 

Appreciated

[Nic]

With Javascript like described here:

http://www.tinkerforge.com/en/doc/Software/Bricklets/LCD20x4_Bricklet_JavaScript.html#BrickletLCD20x4.setCustomCharacter

 

Or y can set it directly in Brick Viewer version >= 2.0.1

http://www.tinkerforge.com/de/doc/_images/bricklet_lcd_20x4_brickv.jpg

 

I assume for the mom the Mqtt proxy doesnt support it:

http://www.tinkerforge.com/en/doc/Software/Brick_MQTT_Proxy.html#supported-device-topics

[rwblinn]

Thanks for reply.

For MQTT

Looked at source brick-mqtt-proxy.py and noticed work in progress (see code snippet). So will wait for an updated brick-mqtt-proxy.

Any timelines when special chars will be supported?

 

# FIXME: get_custom_character and get_default_text need special handling
class BrickletLCD20x4Proxy(DeviceProxy):
GETTER_SPECS = [
... 
]
SETTER_SPECS = [
...
(set_custom_character', 'custom_character/set', ['index', 'character']),
...
]

 

[photron]

It's not work in progress. You can use it without the getter. The documentation for the setter is missing by accident. I'll fix that.

 

As the documentation for the set_custom_character function says, you need to provide the custom character shape as a bitmask. The documentation has an example for a capital H.

 

Here's setting the first custom character (index 0) to an arrow-up shape:

 

mosquitto_pub -t tinkerforge/bricklet/lcd_20x4/SCD32/custom_character/set -m '{"index":0, "character":[4,14,21,4,4,4,4,4]}'

 

Now to write this custom character (index 0) to the display you need to write a character with byte representation 8. This can be done with the Unicode escape sequence \u0008 in JSON:

 

mosquitto_pub -t tinkerforge/bricklet/lcd_20x4/SCD32/write_line/set -m '{"line":0, "position":0, "text":"\u0008"}'

 

I'll add to my TODO list to add a custom character example to the API bindings.

[rwblinn]

Thanks a lot for the information and swift reply.

Have integrated this into a Node-RED Flow and its working fine.

 

For those interested in Node-RED, look up my website http://www.rwblinn.de > IoT > Node-RED > Category TinkerForge.

One of the Node-RED flows uses the Bricklets LCD20x4, Temperature, Humidity, Barometer. Here some screenshots: