Fast (or slow, as required) scrolling text on a 8 x 32 dot matrix display module.

[Hairy Animal]

These dot matrix displays are driven by four MAX7219 devices daisy-chained together. They can be driven with a simple three-pin serial interface (Din, Cs & Clk) from any PICAXE device including the 08M2 (though the attached code may not work with that).

The displays come in a variety of forms from single 8 x 8 displays which can be connected to make a set of four, to the above which is very compact and has the LED module soldered over the MAX7219. An alternative version has the LED modules in sockets allowing them to be removed. Prices start from about £5, by way of an example, this pair cost £11 for two: https://amzn.eu/d/iWJdIt5 .

The attached code originally by @BESQUEUT but with significant recent improvements by @AllyCat uses a 20M2 to drive the display with (almost) any number of text strings and has the full ASCII character set available. The attached code also features, if required, real time day, date & time display if a DS3231 RTC device is available (using the I²C bus). Other variables could also be displayed.

This video shows a demo of the characters and time/date. The variations in brightness are due to phone not being locked to a specific setting.

Particular thanks to @AllyCat for his perseverance in getting this right.

 

[AllyCat]

Hi,

Here's an alternative TEST version of the SPI driver code, which uses less memory and fewer precious registers. If it works well, I'll edit it to remove the unnecessary code and comments. If it doesn't, I'll probably just delete this post.

Cheers, Alan.