Paul Boddie's Free Software-related blog
Paul's activities and perspectives around Free Software
A Small Update
Following swiftly on from my last article, I decided to take the opportunity to extend my framebuffer components to support an interface utilised by the L4Re framework’s Mag component, which is a display multiplexer providing a kind of multiple window environment. I’m not sure if Mag is really supported any more, but it provided the basis of a number of L4Re examples for a while, and I brought it into use for my own demonstrations.
Eventually, having needed to remind myself of some of the details of my own software, I managed to deploy the collection of components required, each with their own specialised task, but most pertinently a SoC-specific SPI driver and a newly extended display-specific framebuffer driver. The framebuffer driver could now be connected directly to Mag in the Lua-based coordination script used by the Ned initialisation program, which starts up programs within L4Re, and Mag could now request a region of memory from the framebuffer driver for further use by other programs.
All of this extra effort merely provided another way of delivering a familiar demonstration, that being the colourful, mesmerising spectrum example once provided as part of the L4Re software distribution. This example also uses the programming interface mentioned above to request a framebuffer from Mag. It then plots its colourful output into this framebuffer.
The result is familiar from earlier articles:
The spectrum example on a screen driven by the ILI9486 controller.
The significant difference, however, is that underneath the application programs, a combination of interchangeable components provides the necessary adaptation to the combination of hardware devices involved. And the framebuffer component can now completely replace the fb-drv component that was also part of the L4Re distribution, thereby eliminating a dependency on a rather cumbersome and presumably obsolete piece of software.