If you’re looking for a reminder of how powerful the tiny microcontrollers that run our everyday gadgets have become, check out the work impressive work [Audun Wilhelmsen] has done to get DOOM running on the Nordic Semiconductor nRF5340. This is the sort of Bluetooth SoC you’d expect to find in a headset or wireless keyboard, and yet it’s packing a 128 MHz processor that can go head to head with the Intel 486 that the iconic first person shooter recommended you have in your old beige box PC.
That said, porting the open source shooter over to the nRF5340 wasn’t exactly easy. The challenge was getting the game, which recommended your PC have 8 MB back in 1993, to run on a microcontroller with a paltry 512 KB of memory. Luckily, a lot of the data the game loads into RAM is static. While that might have been necessary when the game was running from a pokey IDE hard drive, the nearly instantaneous access times of solid state storage and the nRF5340’s execute in place (XIP) capability meant [Audun] could move all of that over to an SPI-connected 8 MB flash chip with some tweaks to the code.
In general, [Audun] explains that many of the design decisions made for the original DOOM engine were made with the assumption that the limiting factor would be CPU power rather than RAM. So that lead to things often getting pre-calculated and stored in memory for instant access. But with the extra horsepower of the nRF5340, it was often helpful to flip this dynamic over and reverse the optimizations made by the original developers.
On the hardware side, things are relatively straightforward. The 4.3″ 800×480 LCD display is connected over SPI, and an I2S DAC handles the sound. Bluetooth would have been the logical choice for the controls, but to keep things simple, [Audun] ended up using a BBC micro:bit that could communicate with the nRF5340 via Nordic’s own proprietary protocol. Though he does note that Bluetooth mouse and keyboard support is something he’d like to implement eventually.
If some of the software tricks employed by this hack sounded familiar, it’s because a very similar technique was used to get DOOM running on an IKEA TRÅDFRI light bulb a week or so back. Unfortunately it must have ruffled some feathers, as it was pulled from the Internet in short order. It sounds like [Audun] got the OK from his bosses at Nordic Semiconductor to go public with this project, so hopefully this one will stick around for awhile.
