tusb_libdlo

This is the libdlo DisplayLink library with some optimizations, ported to TinyUSB - I split it out from PicoGraph after some interest. libdlo is useful on microcontrollers because it allows them to support very high resolution devices without spending much memory on the microcontroller - the framebuffer is on the other side, and it supports accelerated blits and fills. This library supports DisplayLink DL-1x0/DL-1x5 USB adapters.

Layout

.
├── docs/                 # Original libdlo documentation
├── examples/             # Firmware examples
└── src/                  # tusb_libdlo library target and public headers

Using the Library

tusb_libdlo links against the Pico SDK tinyusb_host target and enables the TinyUSB endpoint-transfer API required by the port.

Build options:

option	default	effect
TUSB_LIBDLO_COMMAND_BUFFER_SIZE	16384	USB command buffer size in bytes. The buffer is split into two halves so encoding the next commands overlaps the in-flight bulk transfer.
TUSB_LIBDLO_16BPP_SCANOUT	OFF	Run the device in 16bpp scanout mode and skip the 8bpp fine-detail plane: roughly 35-40% less USB traffic at RGB565 fidelity instead of the split-plane 24bpp mode.
TUSB_LIBDLO_RLX	ON	Use the af 6b mixed raw/run-length encoding for pixel uploads; the smallest of raw, RLE, and mixed is chosen per 256-pixel chunk.

Examples

I included some examples, because - why not. The repository includes two Pico 1 examples:

pico_gc_mystify enumerates all DisplayLink devices and initializes all of them, then displays a screensaver.

pico_tv_typewriter is a dumb tv typewriter, but the pico W build supports telnet over WIFI (that's the aquarium demonstration on telehack in the gif).

The example dependencies are marked update = none in .gitmodules, so projects embedding this repository as a submodule never pull them, even with --recursive. To build the examples, opt in explicitly with --checkout:

Root Build

git submodule update --init --checkout --recursive
cmake -S . -B build -DPICO_BOARD=pico
cmake --build build --target pico_tv_typewriter
cmake --build build --target pico_gc_mystify

The UF2s will be written under build/examples/. Set TUSB_LIBDLO_BUILD_EXAMPLES=OFF to configure the library target only.

Hardware Notes

The examples expect the Pico USB port to run as a TinyUSB host. Use a powered USB hub or equivalent host wiring. The typewriter needs a DisplayLink adapter and a USB keyboard; the mystify example only needs the DisplayLink adapters.

Default Art

The checked-in ANSI art was generated from Wikimedia Commons Raspberry Pi Pico oblique.jpg by Phiarc, licensed CC BY-SA 4.0.

License

This repository inherits Picograph's repository-level GNU GPL version 2 license for its packaging, examples, and other code without a more specific file-level license; see LICENSE.

The libdlo sources retain DisplayLink's original GNU Library GPL version 2 notices; see COPYING and AUTHORS. Flanterm and TinyUSB are pulled as submodules under their upstream licenses. The generated Pico ANSI art is a transformed version of the CC BY-SA 4.0 Wikimedia Commons photo described above.