TEC-IST Aims to Push a Raspberry Pi RP2040 to Drive a Full HD HDMI-Capable Desktop-Style System

Pseudonymous maker "TEC-IST" has a dream: turning the Raspberry Pi RP2040's ability to output a DVI signal over an HDMI port into the ability to run a Full HD display at its native 1,920×1,080 resolution — and has turned the microcontroller into a desktop computer, complete with Ethernet connectivity, to prove the concept.

"Microcontrollers have begun to rival early PCs and retro gaming consoles in measures like speed and memory capacity, and even leapfrog them with new capabilities like multiple cores and wireless connectivity," TEC-IST explains of the project's background. "One area that still seems a bit lacking is video output. Sure, the ability to connect a smallish LCD via I2C or SPI is normal, but can these little marvels do more? With a little spicier circuit, I think so."

TEC-IST's work is inspired by Luke Wren's Pico-DVI, which bit-bangs a DVI signal over an HDMI port to offer a usable video output from the Raspberry Pi Pico or other Raspberry Pi RP2040-based development board. While Pico-DVI is fully functional, though, it's limited to relatively low resolutions and color depths by the constrained resources of the microcontroller on which it runs. TEC-IST's idea, then, is simple: what if those constraints are removed?

"[Wren] validated the output up to 372Mbps (good enough for HD 720@30Hz)," TEC-IST explains. "That leaves some resolution milestones unexplored — for example, FHD [Full HD] 1,920×1,080@60Hz × 24-bit color depth = 2.985984Gbits/second not including control signals and blanking overhead — approaching an order of magnitude larger."

To achieve that speed-up, TEC-IST has designed a board which adds some extra resources to the RP2040: an external RGB to HDMI encoder, external dynamic RAM (DRAM) to serve as a frame buffer, and the connectivity required to be a functional system. "I put together an RP2040 'desktop' board," the maker explains, "complete with Ethernet, USB-C in with 'real' (negotiated) power (not the USB A-to-C requirement or resistor hacks), a blingy gold sink board HDMI output with video and sound, i2s audio also piped to an onboard speaker, as well as a microphone input, two USB A for mouse and keyboard, a headphone jack, and hardware cutoff switches for mic and speaker, as well as compatibility and quality of life options. Perhaps a good dev kit if you want to build on FreeRTOS, Zephyr, etc."

In addition to the full-featured board, which at the time of writing had not been tested, TEC-IST has also designed a cut-down version with a production cost around half that of the full board design. "Maybe something like this would be of interest to retro gamers wanting to plug their RP2040-based emulator into a TV/monitor," the maker muses. "Maybe piping a terminal to modern displays via hardware? Sometimes it's just fun to explore the limits."

The Gerbers for the project have been published to GitHub under an unspecified open source license, though TEC-IST warns that anyone looking to build a board should "double-check everything, as I have not had these built/tested!"