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Packet Trace: Schedule Write

Writing a weekly schedule layer is the largest single write this protocol does. It exercises three things nothing else does: a 59-byte frame, three-way MTU splitting, and a configuration commit that must not be a constant.

Overview

  1. 42-byte payload — 7 days × 6 bytes, always the whole layer.
  2. Three BLE writes — 20 + 20 + 19 bytes. Not two.
  3. Class 10 SET, OpSpec 0xB3, Object 84, SubID 1000 + layer.
  4. A commit afterwards, built from the pump's current overview.

1. Schedule data structure

A layer is 7 days, Monday first, 6 bytes each — 42 bytes, always sent whole. There is no partial update: to change one day you read the layer, edit that day's six bytes, and write all 42 back.

Day format (6 bytes): 

[Enabled] [Action] [Start-H] [Start-M] [End-H] [End-M]
- Enabled: 0x01 (yes) or 0x00 (no) - Action: 0x01 (start/run) or 0x00 (stop) - Times: hours 0–23, minutes 0–59, as plain bytes

Times are hour and minute bytes. They are not minutes-since-midnight; an implementation that packs them that way writes garbage the pump accepts.

Example: Monday 06:30–08:30, other days disabled

01 01 06 1E 08 1E     Mon   enabled, run, 06:30 → 08:30
00 00 00 00 00 00     Tue
00 00 00 00 00 00     Wed
00 00 00 00 00 00     Thu
00 00 00 00 00 00     Fri
00 00 00 00 00 00     Sat
00 00 00 00 00 00     Sun

0x1E is 30 minutes.

2. Build the command

Target: Object 84 (0x54), SubID 1000 + layer (layer 0 → 0x03E8).

APDU:

[0x0A]              Class 10
[0xB3]              OpSpec: SET, long payload
[0x54]              Object 84
[SubH][SubL]        SubID, big-endian
[0x00]              Reserved
[0xDE][0x01][0x00]  Type 222 header
[0x00][0x2A]        Size: 42
[42 bytes]          The layer

Full frame (59 bytes) for the example above, layer 0:

Section Bytes Value
Header 0–3 27 37 E7 F8
APDU head 4–5 0A B3
Object / SubID 6–8 54 03 E8
Reserved 9 00
Type / size 10–14 DE 01 00 00 2A
Data 15–56 01 01 06 1E 08 1E 00 …
CRC 57–58 E6 1E

Note the length byte is 0x37 (55), not 0x3B (59). It is not the frame length: it counts the bytes between itself and the CRC — service ID, source address and the 53-byte APDU. Total frame = length + 4.

27 37 E7 F8 0A B3 54 03 E8 00 DE 01 00 00 2A 01 01 06 1E 08 1E 00 00 00 00
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
00 00 00 00 00 00 00 E6 1E

3. BLE packet splitting

59 bytes does not fit the 20-byte MTU. Split into as many chunks as it needs — here, three:

Chunk 1 (bytes 0–19)

27 37 E7 F8 0A B3 54 03 E8 00 DE 01 00 00 2A 01 01 06 1E 08

Chunk 2 (bytes 20–39)

1E 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00

Chunk 3 (bytes 40–58)

00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 E6 1E

Pace roughly 50 ms between writes.

Two-chunk splitting silently truncates this frame

A splitter written as "first 20 bytes, then the rest" looks correct on every 24-byte control packet and fails here: the second "chunk" is 39 bytes, which exceeds the MTU. That shipped in this library, and the schedule write was the only casualty — everything else was small enough to hide it. Loop over the frame in 20-byte slices; do not special-case two.

4. Commit

The write does not persist on its own. A configuration commit follows, and it carries the pump's whole ClockProgramOverview — including the schedule's own enabled flag at byte 4.

Read Object 84 Sub 1, modify only what you mean to change, write it back. A hardcoded commit blob with 0x00 in byte 4 disables the schedule you just wrote. If the overview cannot be read, send no commit: a lost flush is recoverable, a fabricated schedule state is not.

See 04_set_mode.md for the commit frame.

5. Response

The pump acknowledges with a short Class 10 frame, opspec 0x01 or 0x81:

24 06 F8 E7 0A 01 00 00

It does not echo the schedule back. An implementation waiting for a 42-byte echo waits forever.

6. Common pitfalls

  1. Assuming two chunks. Three are needed here. See above.
  2. No pacing. Chunks sent back to back overflow the pump's buffer.
  3. Length byte. It describes the whole frame, not the chunk — every chunk after the first is raw continuation bytes with no header of its own.
  4. CRC. Computed over frame[1:-2] of the assembled 59 bytes, before splitting. CCITT 0x1021, init 0xFFFF, final XOR 0xFFFF.
  5. Forgetting the commit, or sending a fixed one.
  6. A schedule over a stopped pump. With the pump stopped and the schedule enabled, every window opens with the motor idle and no fault is reported. The schedule alone does not start the pump.

7. Verification

Read the layer back:

27 07 E7 F8 0A 03 54 03 E8 [CRC]

The reply should contain the same 42 bytes. Verify against what you sent — this write has no clamping behaviour, so a mismatch is a real failure rather than the pump exercising judgement.