Pikocore v2: new samples without new firmware

Replacing the pikocore's samples should not require quite as much work as playing it.

That was the awkward part of the original firmware. In Pikocore v1, the samples and the program were packed into the same firmware file. The legacy web uploader could make that file for you, but a new set of sounds still meant making and flashing a new .uf2. A sample change felt like a firmware update because technically it was one.

Pikocore v2 changes that! The firmware and sample bank now live separately, and the Pikocore can talk to a browser over USB. Version 2 arrived in June, and has had several improvements since (now on v2.4). Along the way I rebuilt the real-time stretch and gave the clock input much steadier timing.

the browser became part of pikocore

The browser sample manager is forked from the genius open-source work of @dessertplanet, on MLRws-web. MLRws-web project is a browser companion for MLRws on the Music Thing Modular Workshop Computer, a six-track sample-cutting instrument with on-card storage and a web editor, also a work of incredible genius.

The idea was wonderful: a small open musical computer can expose its samples to a useful browser interface. In v2, I have adapted that work to Pikocore's flash layout and USB serial protocol.

The other benefit is that the manager runs locally! Your audio does not visit a server before it reaches the Pikocore. The browser decodes it, converts it, and writes the finished bank directly over USB. Makes the whole experience much faster, and less error-prone (no longer depends on my server!).

what the new workflow looks like

To get started, open the Pikocore v2 firmware and sample loader in a browser with Web Serial support, such as Chrome or Edge (and recently, Firefox, I believe). The question-mark button opens a tour, but the basic workflow is:

1. Choose the firmware that matches your Pikocore. The normal Infinite Digits version is 16 MB, with 4 MB and 2 MB builds for other boards.
2. Download the .uf2, put Pikocore into BOOTSEL drive mode, and copy it to the RPI-RP2 drive. Once recent v2 firmware is installed, the loader's Boot button can ask the device to enter that mode.
3. Press Connect and choose the Pikocore serial port. The browser reads the bank already on the device, so you edit what is actually there.
4. Add audio files or drag them into the page. The loader converts them and shows waveforms, names, BPM, beat counts, duration, and size.
5. Preview samples, correct their names or timing, change their order, or remove them. A meter keeps track of the remaining flash.
6. Press Upload to write the bank back. Read reloads it later, and Erase clears it when that is really what you intended.

Two filename tricks are still useful. bpm150 means 150 BPM and beats8 means eight beats. Without them, the browser makes an estimate that you can correct before uploading.

default samples

Moving from v1 to v2 replaces the old firmware and samples, so save the audio or keep the stock sample bank nearby. Afterward, changing the instrument is a sample-management job, not a build process.

stretch that actually stretches

The stretch control in v1 was a clever timing trick...but it changed how quickly playback advanced, which was cheap enough for the RP2040 and appropriately rough, but it could sound abrupt while moving.

In v2 I replaced it with a small real-time granular stretcher. Two overlapping grains read the sample at its natural rate while moving through it more slowly. They are crossfaded with interpolated reads. This is still a tiny 8-bit instrument, so the goal is not invisible studio correction. It is a stretch that sounds like Pikocore, keeps pitch steadier, and works while the loop is running.

A little stretch can loosen a loop without dragging its pitch downward. A lot pulls the sound apart and gives the jump, retrigger, and filter controls more material to chew on. It is now an effect I reach for very often.

a clock that is less easily startled

Some newer additions: Version 2.4 is mostly about the clock input. The new clock code filters measured intervals, rejects bounce and isolated bad edges, recognizes missed pulses, and eases phase corrections instead of jumping. It acquires a new tempo when the incoming clock really changes and pauses cleanly when the clock disappears. Pulse input can be set to quarter notes, eighth notes, or sixteenth notes, while ittybittymidi mode follows MIDI clock plus start, stop, and continue.

The v2.4 loader also shows lock state, BPM, jitter, phase error, rejected events, and pulse division. Most people will never need those numbers. I needed them to make the clock boring in the best possible way.

one update for the whole family

Pikocore v2 is not limited to the assembled handheld. It is compatible with the Pikocore XL from Erica Synths, the P4L PIKOCOREURO, and the homemade and remixed instruments collected in The Pikocore Underground. Choose the 2 MB, 4 MB, or 16 MB build that matches the RP2040 board in the instrument.

should I upgrade?

If you use a Pikocore v1, I think the answer is yes. The controls, sequencer, saves, probabilities, button combinations, PO sync, and lo-fi sound are still there. Samples are much easier to replace, stretching is better while the instrument is running, and external clocking is substantially more stable.

When changing a bank takes a few browser clicks, I change banks more often. Pikocore stops being the device with whichever breaks happened to be inside when I last made firmware and becomes something I can quickly prepare for a track, a trip, or an afternoon of making noise.

You can install v2.4 with the browser loader, read the source and releases on GitHub, or start with an assembled Pikocore, the DIY kit, or the bare circuit board.

Then put something strange in it.