mpckit/docs/checkpoint-b.md

Device checkpoint B: round trips through the app

Build plan section 7, after M8. Each project below starts from testdata\device\DemoFile.xpj, a project the device saved, and is changed and exported in the app. Then it is loaded on the MPC Sample.

DemoFile, for reference:

• Pads: A01 kick, A02 snare, A03 hat 1, A04 hat 2 (A03 and A04 in mute group 1), B01 pad loop, B02 bass.
• Sequence 01 "Intro" (110 BPM, 2 bars, notes on A01–A03) and Sequence 02 (110 BPM, 4 bars, notes on A01–A04).

For each project: Load DemoFile, make the changes, set the project name, then Export to folder (straight onto the card) or Export zip. Load DemoFile fresh for each one; don't build them on top of each other.

Projects

MpckitB1: no changes (B1)

Only rename to MpckitB1.

On the device: both sequences play exactly as DemoFile does.

MpckitB2: move a pad that has notes (B2)

Drag A01 → A05. The app warns that A01's notes stay on A01; confirm.

On the device: A05 plays the kick. In the sequences the kick is gone, because the notes still point at A01, which is now empty.

MpckitB3: copy across banks, swap pads with notes (B3)

1. Alt-drag B01 → C01 (copy into another bank: drag over the C letter first).
2. Drag A02 onto A03 (swap; the app warns about both pads' notes; confirm).

On the device:

• C01 plays the same pad loop as B01, and B01 still plays.
• A02 plays hat 1 and A03 plays the snare. In the sequences, the snare and hat 1 parts have changed places.

MpckitB4: remove the current sequence, add one in another bank (B4)

1. Sequences tab: select A01 "Intro" → Remove sequence → confirm.
2. Select slot B01 (sequence 17) → Add sequence → name Bridge, BPM 100, length 4.

On the device:

• The list shows Sequence 02 and Bridge (slot 17), and no Intro.
• Which sequence is selected when the project opens? Intro was the current sequence; the app made the lowest remaining slot (Sequence 02) current. This answers open question 7 in the format doc (is currentSequence a slot or a list position?).
• Bridge is empty, 4 bars, 100 BPM.

MpckitB5: shorten a sequence that has notes (B5)

Sequence 02: length 4 → 2 bars (the app asks first; confirm).

On the device:

• Sequence 02 is 2 bars and plays the notes in bars 1–2.
• What happened to the notes from bars 3–4? Lengthen it back to 4 bars on the device: do they come back, or are they gone?

Results

Run on the MPC Sample on 2026-11-11 by bajdev. All five loaded and passed.

Project	Loads	Result
MpckitB1	yes	Worked: plays as DemoFile.
MpckitB2	yes	Worked: A05 plays the kick; the notes stayed on A01.
MpckitB3	yes	Worked: the copy in bank C plays; the swapped pads changed places in the sequences.
MpckitB4	yes	Worked. Sequence 02 (A02) was selected on open.
MpckitB5	yes	Sequence 02 plays its 2 bars correctly. Lengthened back to 4 bars on the device, the notes in bars 3 and 4 are still there and play.

B4 does not settle open question 7. In MpckitB4 the stored list is [Bridge (slot 17), Sequence 02 (slot 2)] and currentSequence is 1, so "slot 1" and "position 1 in the list" both mean Sequence 02.