Wearable Scope Lets Your Fingers Do The Probing

September 3, 2021 by Tom Nardi 14 Comments

For frantic hacking sessions where seconds count, this forearm mounted oscilloscope with fingertip probes built by [aniketdhole] might be just what you need. Well, maybe. It’s not immediately clear why you might want to wear an oscilloscope on your arm, and sticking your fingers inside of powered up electronic devices sounds specifically like something your mother probably told you not to do, but here it is anyway.

The scope consists of an nRF5340 evaluation board in a 3D printed mount, with an SPI-connected Adafruit 2.8″ TFT display on top. With a pair of wires run from the board’s ADC and ground pins, [aniketdhole] just needed a bit of code to glue it all together and show some basic signal visualizations on the display. It’s been tested against PWM signals generated by an Arduino and some potentiometer controlled voltages, but anything much wilder than that is probably a bit too much to ask for from this rig in its current configuration.

In the future, [aniketdhole] wants to add some step-down circuity so you can probe higher voltages than the nRF5340 can handle normally, as well as a shunt to allow current measurement. Once the hardware is in place, the next order of business will be an improved touch-capable user interface that lets the user adjust settings and switch between functions.

Even if you’re not sold on the idea of an arm-mounted oscilloscope, this is still an interesting platform for general wearable experimentation. Throw enough sensors into it, and we’re sure there’s more than a few hackers who wouldn’t mind strapping one of these on.

DOOM Comes To The NRF5340

June 22, 2021 by Tom Nardi 14 Comments

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.

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