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Project update 8 of 8
Hello everybody! I hope you’re all keeping warm this winter. Here’s an update on the Pocket Integrator project since our campaign completed in December.
After we finished the campaign, I finally took some time off for the holidays, hooray! I also had a great time at the Crowd Supply Christmas party. Not every Crowd Supply project is based in Portland, but I live here, and they’re based here, and it was great to spend some face time with the people who’ve been supporting my project all year.
I’ve completed the RP2040 port of the firmware. This has been pretty smooth but still involved some learning and lots of debugging and testing. The most complicated piece was the audio subsystem that generates the shaker tone. The RP2040 is a Coretex-M0 MCU, which doesn’t support vector-processing like the Cortex-M4 chip from earlier versions did. Therefore I’ve had to transition from the really excellent Teensy Audio libraries to a simpler audio approach. The new code employs several of the RP2040’s fancy built in peripherals to produce either white noise for the shaker or a variety of test tones. The tones help me test that we’re generating good levels that are compatible with pro audio gear, without sending any dangerous supersonic frequencies or unwanted noise. Looking at the output on oscilloscope and spectrogram, and listening with my favorite monitors, the results I’m now seeing & hearing are at least as good as the previous version, which I was already pretty pleased with.
I built and brought up the latest board revision (v8), which mainly improves the power subsystem. The Pocket Integrator now runs at a core voltage of 1.8 volts instead of 3.3, which reduces battery consumption significantly. That also lets me replace a noisy buck-boost power converter with a much smoother buck-only converter, resulting in a lower noise floor on the audio jacks. This is the last major change; the next iteration (v9), hopefully the last one, will address a short list of board bugs. (Also, the v8 revision was produced during the Chinese New Year, when the purple department of the PCB factory was on holiday. Because of that, the V8 board has an ugly green/silver color scheme that you wouldn’t want to be seen with. V9 will be purple and gold again!)
The two rubber bands that connect the Integrator to your Pocker Operator are actually neoprene O-ring gaskets of a specific size and thickness. They’re very simple, but you wouldn’t want one to break while you’re playing! So I put a bit of research and stress-testing into the question of whether neoprene is the best material for the job, versus the myriad other O-ring options available such as silicone, nitrile, butyl, ethylpropeline, fluorsilicone…it turns out rubber is complicated! But I’m now convinced that neoprene is in fact the bee’s knees, and I’ve got a supplier lined up for those.
(By the way, if you’re as big a nerd as I am and are curious to know waaaaay too much about rubber, here are a few links I found really interesting: the many kinds of rubber, rubber hardness/softness on the Durometer scale, and WTF is a Durometer anyway?)
I talked over the V8 board with my contract manufacturers, who gave me some great guidance about how to improve the solder masks of certain components for better reliability. We also have been working on the factory QA and testing plan. Interestingly, now that the Global Chip Shortage is easing up and more chips are coming back in stock, some manufactures (including these guys) are suddenly backed up with a rush of delayed orders, some of which have literally been waiting for years! Fortunately these guys are pretty quick and flexible. We’re currently looking at an April manufacturing window, which isn’t really that far away.
Aside from all that, lots of testing! Stress tests: high temperature, heavy G-shock, low battery, et cetera. Also electrical tests, to characterize the power consumption under various conditions & make sure the PI is not a battery-killer. Also the aforementioned audio tests. Also clock stability tests, MIDI jitter tests … every test I can think of, really. Suggestions appreciated!
So that’s the latest Pocket Integrator news. My current schedule is to ship the PI to backers in June, based on the schedule we have for manufacturing and my current engineering velocity. I’m still very excited to get this to you, and very grateful for your patience and continued support!