What is it?

Prototype hackable real time clock and scrolling text message board with RPI Pico micro-controller (MCU). Also functions as LCD tester. Two HD44780 LCD displays configured in 8 bit parallel operation. DS1307 real-time clock RTC. RTC is set via timestamp on compilation. Golang source code - compiled with tinygo.

Why did you make it?

I started making something to test LCD displays. Making a clock was an obvious application after the LCD testing was done. After testing connecting multiple LCDs, it made sense to have something besides the time on the other screen.

What makes it special?

It's a unique hand-soldered prototype.

It's left to the user to decide what they want it to do. It invites the user to reconfigure it as they desire - the helper program supports reconfiguration of the 'Mode' or what is displayed on the LCD (clock or scrolling message) the update interval or scroll rate, as well as the mapping of GPIO pins to LCD pins via command line flags. This avoids the need to manually edit the source code in order to reconfigure the device to work with a different LCD or to change what is displayed on any LCD or how it is displayed.

The source code is in golang and compiles with tinygo.

Tinygo only supports single-threaded operation, though support for multiple cores is planned. As well, the subset of golang standard libraries which will work with tinygo is slightly limited. For instance, encoding/json wasn't working. This presented some challenges for configuration, as the obvious method of setting a json config as a string variable via ldflags and then parsing that at runtime was simply not working. This was ultimately solved with a bit of meta-programming. The helper or wrapper program for the workflow which is included with the source code will generate a help menu including different flags which can be set for the program that will be compiled for and written / flashed to the microcontroller. Some of these flags are set at compile time with ldflags and parsed at runtime, but others are essentially set via creation of a modified version of the source code which is then compiled and flashed on the microcontroller.

Note that this helper wrapper program is only guaranteed to work on linux, currently. It is not required to use it, you can always edit the source code by hand, if you prefer, in order to to change the configuration.