There’s a new GLCD library to drive the 128×64 graphics LCD display on the Graphics Board. The library is called, wait for it… GLCDlib – with a wiki page and a web interface to the source code in subversion. There’s also a ZIP archive snapshot, but it probably won’t get updated with each future subversion change. For some notes about using subversion (“svn”), see this post.

The main class is “GLCD_ST7565”, it has the following members:

(some longer entries above were truncated, see the website for the full version)

The settings in this library have been hard-coded for use with the Graphics Board, which uses ports 1 and 4 to drive this display. If you want to use this with other I/O connections, you’ll need to change the #define’s at the top of the “GLCD_ST7565.cpp” source file in the library.

Here is the demo used in an earlier post, now included as “glcd_demo.pde” example sketch in the library:

This produces an output screen similar to this image. Note the use of flash-based string storage with “PSTR” to reduce RAM usage. It not an issue in this example, but more strings tend to rapidly consume RAM, leading to strange and hard-to-find bugs.

The nice thing about GLCDlib, is that you can also use it over wireless. There is a “GLCD_proxy” class, which sends all graphics commands out to another node. Each command is sent as a packet, complete with ACKs, retries, and resends to deal with lost packets.

The “JeePU.pde” example sketch implements the “host”, i.e. a JeeNode with Graphics Board, listening to incoming wireless requests. The “JeePU_demo.pde” sketch shows how to talk to such a remote JeePU node.

Because the transport layer (i.e. wireless or other comms mechanism) is separated out from the main graphics primitives, it is very easy to switch between a locally-connected GLCD and a remote one on a JeePU node. The magic is contained mostly in these lines:

The only other change needed to use a remote GLCD is to add these lines at the start of setup():

See the JeePU_demo.pde sketch for an example of how this can be used.

The JeePU node should be running in its own RF12 net group, because clients use broadcasts to send out the graphics commands. They do not need to know the node ID of the JeePU, just its net-group. This also means that multiple GLCD proxy clients can run at the same time, and each could be adjusting a specific part of the same JeePU display … whee, a multi-node status display!

One of the advantages of running the Graphics Board as a JeePU node, is that the other nodes don’t need to load the entire GLCDlib code, in particular they avoid the 1 Kb RAM buffer needed to drive the display.

The graphics code is based on what used to be the ST7565 library by Limor Fried at AdaFruit, which was in turn derived from public domain code attributed to “cstone@pobox.com”.

Several great extensions (and a couple of bug fixes) for the core graphics routines were written by Steve Evans (aka tankslappa on the wiki and forum). Steve also implemented the remote/proxy code and the JeePU “host” and JeePU_demo “client”.

I just hacked around a bit on all that, including renaming things and adding an ACK mechanism to the RF12 wireless layer.

This code is likely to change and extend further, as we come up with more things to do with the current implementation. But for now, enjoy :)

Update – all the code is now at https://git.jeelabs.org/glcdlib.