seismo-relay/docs/micromate_protocol_reference.md

Micromate Protocol Reference — Thor / Micromate Series IV, live wire protocol

Sibling to instantel_protocol_reference.md (Series III, "the Rosetta Stone") and idf_protocol_reference.md (Series IV file format). This document covers the Series IV live device protocol — what the unit says over the wire, as opposed to what it writes into a .IDFW.

Status (2026-09-23): opening session. Everything below was established in a single bench session against one unit. Treat it as a strong start, not a settled spec — in particular, everything here comes from one unit, over USB, with no events stored.

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The headline

A Micromate running the Blastware firmware answers Series III command frames.

An unmodified Series III POLL (SUB 0x5B), built by minimateplus.framing.build_bw_frame with no changes at all, produced a complete two-step probe/data cycle. Ten Series III read commands were then tried and all ten answered, every one obeying the Series III response-SUB rule.

⚠ That qualifier is load-bearing, and it was discovered after the fact. Instantel ships the Micromate in two firmware lines:

firmware	Instantel's own description
11.0CB	"Utilize with Blastware"
11.0BD	"Utilize with THOR, Vision, Vision II"

The bench unit reports 11.0CB — the Blastware build. So the clean Series III behaviour above is very likely because the unit is in Blastware mode, not because the Micromate natively speaks Series III. Nothing here should be assumed to hold on a 11.0BD unit until tested.

This reframes the project. The question is no longer only "what is the Series IV protocol" but "which firmware line do we target, and does one of them let the existing Series III stack drive the whole fleet?"

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Firmware — the variable nobody knew was a variable

This explains a production problem TMI has lived with: two ACH servers, two machines, and units that will not cross over. It is not a misconfiguration. Instantel ships different firmware for different host software, and the wire protocol differs with it.

Fleet audit (physical, 2026-09-22/23)

unit	firmware	line	location
UM11719	11.0CB	Blastware	Ped Bridge Loc 2
UM6047	11.0CB	Blastware	Brookville Loc 9
UM12947	11.0CB	Blastware	bench
UM14133	11.0CB	Blastware	Pitt-Music Bldg Loc 1
UM11402	11.0BD	Thor	Ped Bridge Loc 1
UM20147	11.0BD	Thor	bench
UM13981	11.0AK	pre-split	RKM Loc 1
UM20146	11.0AK	pre-split	Karns Loc 2
UM12420	10.90GC	pre-split	RKM Loc 2

4 Blastware / 2 Thor / 3 pre-split. The Blastware line is already the plurality, which makes "standardise on Blastware" less disruptive than it first appeared.

A store-derived audit (firmware is recorded in every .sfm.json sidecar as extensions.idf_report.version) agreed with the physical audit on 7 of 9. The two that differed — UM6047 and UM14133 — are the most recently deployed units, reflashed after their last stored event. Useful technique: the fleet's firmware history is reconstructable from the store without touching a unit, but it lags reality by one deployment.

Firmware is not stable per-unit over time — five of nine have been reflashed at least once. Any fleet-wide claim needs a fresh audit.

⚠ Retraction: firmware line does NOT determine Thor compatibility

An earlier draft of this document suggested that UM12947's trouble with Thor was explained by its being on the Blastware build. That is not supported.

Ped Bridge runs UM11402 (11.0BD) and UM11719 (11.0CB) side by side, both deployed 2026-04-20, and both call Thor successfully — UM11719 has 331 Thor-collected events in the store while on 11.0CB, through 2026-08-23.

So a Blastware-line unit does feed Thor. Whatever the CB/BD split changes, it is not "which host software can collect from it", and UM12947's specific problem remains unexplained.

What is actually established: a 11.0CB unit answers Series III command frames. Whether a 11.0BD unit does is untested — and UM20147 (11.0BD) is on the bench, which makes that a direct A/B away.

The version is readable over the wire from SUB 0x01 as two separate ASCII runs — "0CB" then "11" — with no single concatenated string.

The strategic fork

• Option A — standardise the fleet on the Blastware line. Every unit, MiniMate and Micromate alike, then speaks Series III, and the existing minimateplus/ stack drives all of it. One protocol, one call-home receiver. Dramatically cheaper if it holds up.
• Option B — reverse-engineer the Thor line (11.0BD) and support both.

Option A is the shortcut, but it is unproven and carries real unknowns, all of which are cheap to answer on the bench and expensive to discover later:

1. What file format does a 11.0CB unit produce? If it emits Blastware binaries rather than .IDFW/.IDFH, the (now exact) Series III decoder applies and the IDF codec becomes a legacy path. Not a loss — we have both — but it changes what the ingest pipeline sees.
2. Does Thor still work with a 11.0CB unit? If not, flashing a production unit breaks data collection until the replacement path exists.
3. Are any Micromate-specific capabilities lost on the Blastware line?
4. Is the flash reversible in the field, and what does it cost in downtime?

How this was obtained

No Thor, no modem, no Windows machine. The Micromate exposes its protocol on a USB CDC-ACM virtual serial port:

ID 2504:0300 Instantel Inc. MICROMATE COM PORT
driver: cdc_acm          ATTRS{serial}=="V1.00"
→ /dev/ttyACM0

Plain CDC ACM, so no vendor driver and no proprietary USB layer — any host that can open a serial port can talk to the unit.

Baud is irrelevant over USB. Identical byte-for-byte responses at 38400 and 115200; CDC-ACM ignores the line rate. TMI provisions Micromate modem links at 115200 (Series III uses 38400) — that matters for the cellular path, not for USB.

The device never speaks first. 20 s of passive listening on an idle open port produced zero bytes. It is strictly request/response.

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Physical + framing layer

Requests — Series III format, unmodified

Every frame in this session was produced by build_bw_frame(sub, offset) with no Series IV changes, and the device accepted all of them:

[ACK 0x41] [STX 0x02] [10 10] [flags 00] [SUB] [00] [00] [offset] [params×10] [chk] [ETX 0x03]

⚠ Only the doubled BW_CMD (10 10) form has been exercised. Whether other literal 0x10 bytes inside params require stuffing is untested — none of the probes sent carried one.

Responses — Series III minus the DLE prefix

Series III:   [DLE 0x10] [STX 0x02] … [chk] [ETX 0x03]
Micromate:              [STX 0x02] … [chk] [ETX 0x03]      ← no leading DLE

This single byte matters operationally: Blastware's parser locates frames by scanning for DLE+STX, so it will never find a frame boundary in Micromate traffic no matter what else is correct. That is a structural reason a Micromate cannot call into a Blastware ACH server, independent of any baud mismatch.

Response payload header

[0] CMD    0x00          same as Series III
[1] flags  0xC5          ← Series III uses 0x10.  Constant across all 10 SUBs.
[2] SUB    0xFF − request_SUB
[3] PAGE_HI
[4] PAGE_LO
[5+] data

Checksum — the DLE-aware variant

chk = sum(b for b in payload if b != 0x10) & 0xFF

Confirmed on every frame captured. The POLL probe response contains no 0x10 and so cannot distinguish plain SUM8 from the DLE-aware form; the POLL data response contains a 0x10 at payload offset 42, and only the DLE-aware rule matches there. This is the same checksum Series III uses for its 5A bulk-stream and write frames — not the plain SUM8 of ordinary Series III reads.

The probe response carries the data length

Series III hardcodes DATA_LENGTHS per SUB. On the Micromate the probe response tells you, as a uint16 BE at payload[8:10]:

⚠ Corrected 2026-09-23. An earlier draft read this as a single byte at payload[9]. That is right only while the high byte is zero, and it is catastrophically wrong for SUB 0x1A, whose real length is 0x082C = 2092 — read as a byte it gives 44, a 47× under-read. Always read the pair.

SUB	command	payload[9]	Series III constant
0x15	serial number	0x0A	0x0A ✓
0x01	device info	0x98	0x98 ✓
0x1C	monitor status	0x2C	0x2C ✓
0x06	storage range	0x24	0x24 ✓
0x2C	call-home config	0x7E	0x7C ✗ differs by 2
0x08	event index	0x5A	—
0x1E	event header	0x08	—
0x1A	compliance config	0x082C (2092)	—
0x0A	waveform header	0x00	— (no event context)
0xFE	full config	0x00	— (see note)

Four of four known Series III lengths match exactly. Read the length from the probe rather than hardcoding it — it is free, and it already caught the call-home divergence.

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Confirmed commands (read-only)

All ten below answered with a correct 0xFF − SUB response. Nothing that writes, erases, or changes monitoring state has been sent to a unit.

SUB	RSP	Command	Data proven
0x5B	0xA4	POLL / handshake	yes — ID block
0x15	0xEA	Serial number	yes — UM12947
0x01	0xFE	Device info	yes — 152 B
0x2C	0xD3	Call-home config	yes — 126 B
0x1C	0xE3	Monitor status	yes — 44 B
0x06	0xF9	Event storage range	yes — 36 B
0x08	0xF7	Event index	probe only
0x1E	0xE1	Event header / first key	probe only
0x0A	0xF5	Waveform header	probe only
0x1A	0xE5	Compliance config	probe only

Decoded so far

SUB 0x15 — serial. ASCII, null-terminated: UM12947.

SUB 0x5B / 0x01 — identification strings. Instantel\0 and MM/ISEE/S/IO (MicroMate / ISEE standard). 0x01 also carries eight consecutive 3f 80 00 00 float32 values (= 1.0f) — almost certainly per-channel calibration/scale factors, by analogy with Series III's geo_hardware_constant. Unverified.

SUB 0x1C — monitor status. Series III field offsets apply unchanged:

field	offset	read
battery × 100	payload[-10:-8] uint16 BE	0x017D → 3.81 V
memory total	payload[-8:-4] uint32 BE	15,000,000
memory free	payload[-4:] uint32 BE	15,000,000 (empty)
date	payload[18:22]	day 23, month 9, year 0x07EA = 2026

The battery reading independently corroborates: Thor's own event reports for these units print BatteryLevel : 3.8 volts.

SUB 0x2C — call-home config. Contains the ASCII string RADIO RING. Worth flagging: that is the exact string seen in the RV50 ALEOS_SERIAL debug during the BE12599 incident — 'ATQ1^MATE0^MATS0=2^M^MRADIO RING^M'. So this block holds the modem dial / answer strings, and it is the most directly relevant command to the call-home-receiver goal. Field layout not yet mapped; Series III's map (raw[5] enabled, raw[6:46] dial string) is a starting hypothesis only, and the length already differs (0x7E vs 0x7C).

SUB 0x06 — storage range. All zeros on this unit, consistent with memory free == memory total. Series III reads first/last event keys from the final 8 bytes; untestable until the unit holds events.

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The event chain — walked end to end (2026-09-23, 5 events)

With 5 events on the bench unit (4 waveform + 1 histogram), the Series III browse walk works unmodified:

1E (all-zero params)        -> first key + size
  0A (key)                  -> partial record, histogram only
  0C (key)                  -> 210-byte waveform record
1F (all-zero params/browse) -> next key + size
  ... repeat ...
1F                          -> all-zero key = NULL SENTINEL, chain ends

The sentinel terminated correctly after exactly 5 events.

Event keys are sequential, not addresses

055d4a81  055d4a82  055d4a83  055d4a84  055d4a85

This is a real divergence. Series III keys are flash-buffer addresses (01110000, 011121F2, …) that advance by the event's byte length, which is why its 5A chunk walk is address-arithmetic. Micromate keys are a plain incrementing counter. Any port of the Series III download walk must not assume key arithmetic means anything.

The 4 bytes after the key are the event's size

1E/1F return [key 4B][size 4B]. Series III uses that slot as an offset to the next key; here it is a byte count:

key	size	kind
055d4a81	4,076	histogram
055d4a82	11,032	waveform
055d4a83	11,502	waveform
055d4a84	13,424	waveform
055d4a85	8,746	waveform

Consistent with real file sizes (corpus .IDFH ≈ 3.7–25 KB, .IDFW ≈ 8.6–15.8 KB), and the histogram is unmistakably the small one. ⚠ Inferred, not proven: the sizes sum to 48,780 while monitor status reports 57,344 bytes used, so ~8.5 KB of overhead is unaccounted for.

SUB 0x0C — waveform record, and it carries the job metadata

Length 0xD2 = 210 bytes — identical to Series III. Contents confirmed across all 5 events:

• the event key, echoed
• date + time (17 09 07 ea → 23 Sep 2026, then 10 21 → 16:33 — matching the actual bench recording time)
• title note "Location"
• the project string — "Univ of Pitt-1st Yr Housing-Loc1 Ruskin"
• serial "UM12947"
• channel labels Tran / Vert / Long / Mic — the same labels Series III uses, and the same label-relative float32 layout
• per-event float32 peaks: 3.5152, 1.3720, 2.3542, 3.5152, 0.4227 in/s across the five events (varied deliberately during recording)

This closes the biggest open question for the call-home-receiver goal. The job identity strings (project / client / operator / setup) that today arrive only via Thor's .txt sidecar — and which no amount of sample decoding can reconstruct — are available over the wire from 0x0C. A direct-to-SFM event need not arrive with blank metadata.

SUB 0x0A — partial record, histogram only

0x0A returned len = 0x1E (30 B) for the histogram and len = 0x00 for all four waveforms. The histogram payload carries two timestamps and the ASCII string "\r Vert: 0.300 in/s" — structurally the Series III monitor-log partial record (0x2C type), which likewise holds a start/stop pair and a "Geo: <float> in/s" trigger string.

So on the Micromate the division of labour is: 0x0A describes interval-style records, 0x0C describes triggered events. Series III uses 0x0A's response length (0x46 vs 0x2C) to tell real events from boundaries; that discriminator does not apply here.

DLE stuffing in responses — confirmed present

Earlier marked untested. The 0x0C timestamp field contains 10 10, which destuffs to a single 0x10 and yields a sensible clock reading. Responses are DLE-stuffed, so a parser must destuff before applying field offsets.

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A/B: Blastware build vs Thor build (2026-09-23)

UM12947 (11.0CB) and UM20147 (11.0BD) were each put on the bench and given the identical read-only sweep. Both answer Series III command frames.

	UM12947 11.0CB	UM20147 11.0BD
POLL answers	✓	✓
All 10 read SUBs answer	✓	✓
response_SUB = 0xFF − req	✓	✓
DLE-aware checksum valid	✓	✓
Two-step probe/data read	✓	✓
ID string	MM/ISEE/S/IO	MM/ISEE/S
flags byte	0xC5	0x03
0x1C length	0x2C	0x30

The firmware line does not change the wire protocol. One protocol stack can drive the whole fleet regardless of which build a unit is on. This is the single most consequential finding so far: "standardise the fleet on one firmware" becomes an optional convenience rather than a prerequisite for building a call-home receiver.

The two differences that do exist

1. The flags byte identifies the build. Response payload[1] is 0xC5 on the Blastware line and 0x03 on the Thor line, constant across all ten SUBs on both units. That makes firmware line detectable from any response, without reading device info. ⚠ Two units, one each — treat as a strong hypothesis, not a proven encoding.

Note 0x03 is ETX, so on Thor-line units it arrives DLE-escaped as 10 03. A parser that fails to destuff will mis-locate every field by one byte on exactly half your fleet.

2. SUB 0x1C (monitor status) is 4 bytes longer on the Thor line — 0x30 vs 0x2C — with four extra trailing bytes (0f a0 00 00, purpose unknown).

⚠ This breaks relative-to-end parsing. Series III reads battery and memory from the end of the 0x1C block ([-10:-8], [-8:-4], [-4:]). Those offsets are correct on 11.0CB and wrong on 11.0BD — applying them blindly to UM20147 yields a battery reading of 577.92 V. Parse forward from the declared length instead of backward from the end.

With the offsets shifted by 4, UM20147 reads correctly: battery 3.81 V, memory 15,000,000 total and free (no events stored).

Divergences from Series III (running list)

1. No DLE prefix on responses — bare STX.
2. Response flags byte is 0xC5, not 0x10.
3. Call-home config is 126 bytes, not 124.
4. Data lengths are discoverable from the probe response at payload[9]. 4b. Event keys are a sequential counter, not flash addresses. 4c. 1E/1F return the event size, where Series III returns an offset. 4d. 0x0A vs 0x0C split by record type, not by the 0x46/0x2C length discriminator Series III uses. 4e. Response payload[1] (flags) encodes the firmware line — 0xC5 Blastware, 0x03 Thor — where Series III has a constant 0x10.
5. Modem serial rate is 115200, not 38400 (per TMI provisioning practice; not independently verified here).

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The firmware images are unencrypted — and they document themselves

ref-stuff/micromate-firmware/MICROMATE(CB).BIN and MICROMATE(BD).BIN, ~2.77 MB each and within 192 bytes of one another.

• Entropy 6.08 bits/byte — neither encrypted nor compressed. Plain code and data.
• Header is a big-endian vector table, handlers at 0x4010_30xx.
• ~16,700 extractable strings, including the developers' own debug printf format strings with function names intact.

This is a legitimate interoperability reference for hardware TMI owns, and it short-circuits work I had scoped as "only answerable from a live modem capture".

The call-home state machine, verbatim

ACH_NOT_STARTED → ACH_IDLE → ACH_INITIALIZING → ACH_CONNECTING
                → ACH_CONNECTED → ACH_TRANSFER_DATA
                → ACH_RETRY / ACH_QUITTING          (also ACH_STARTED)

Supporting strings:

ACH: Entry StartCallHome()
ACH: CallHome_task ; CheckAliveTime  CANCEL ; TimeBetweenRetries = %d
ACH: CallHome_task ;  !ExpectedCommunicationsDetected() CANCEL ; TimeBetweenRetries = %d
ACH: CallHomeCommectionCompleteProcessing() ACH=%s EAMWC=%s
ACH: %s() three attempts and it's over
ACH: %s() Send CMD_START_MONITOR
ACH: %s() Send CMD_STOP_MONITOR
ACH: Start Ignore request, Call Home is in progress

What this tells us without a single captured packet:

1. Retry limit is three — "three attempts and it's over".
2. ExpectedCommunicationsDetected() gates the session. If the host does not say something the unit recognises, the call is cancelled and rescheduled after TimeBetweenRetries. A homebrew receiver must satisfy this check or units will retry forever — which is exactly the failure mode seen on BE12599.
3. The unit stops monitoring to call home and restarts afterwards (Send CMD_STOP_MONITOR / CMD_START_MONITOR). Relevant to any wedged-unit rescue: the monitoring state around a call is the device's own doing, not ours.
4. Calls are not re-entrant — "Call Home is in progress" is ignored.

Internal command table

CMD_CALLHOME, CMD_CALLHOME_CANCEL, CMD_CALLHOME_CONNECTION_CONFIRMED, CMD_CALLHOME_CONNECTION_COMPLETE, CMD_CALLHOME_SET_SCHEDULE, CMD_CALLHOME_CLEAR_SCHEDULE, CMD_STOP_CALLHOME_FILETRANSFER, CMD_DUTYCYCLE_AUTOCALLHOME, CMD_PURGE_EVENT_FLASH.

CONNECTION_CONFIRMED as a distinct state from CONNECTION_COMPLETE implies a handshake the host must complete before data flows — the concrete shape of ExpectedCommunicationsDetected().

Event delivery — the mechanism, probably

All Events Uploaded
Mark/Unmark File          Delete Marked Events        Marked Events were Deleted
MONITOR::MESG PURGE_EVENT_FLASH BEGIN / END

A marking mechanism exists, alongside a distinct "all uploaded" terminal state. 🔶 Inferred: events are marked as transferred rather than deleted on send, and purging is a separate explicit act. If so, a receiver that fails to mark would see the same events re-offered every call — the question that gates a safe homebrew receiver. Not yet confirmed; needs either a live call-home capture or disassembly around these strings.

A full user manual is embedded

The firmware carries its own HTML help, which documents configuration we would otherwise have to infer:

• Modem mode: Generic (through a modem) vs USB to PC.
• Modem baud: 9600 / 19200 / 38400 / 57600 / 115200 / 230400 — "must match the expected rate of the PC or modem". Confirms 115200 is a setting, not a fixed rate.
• Modem relay + warmup (0–300 s), auxiliary mode, warning/alarm hold.
• Record modes: Waveform, Waveform Manual, Histogram, Histogram-Combo; sample rates 1024 / 2048 / 4096.
• A scheduler downloaded from THOR that can start/stop monitoring, change record mode, trigger a call home, or run a self check on a daily/weekly schedule. Pairs with CMD_CALLHOME_SET_SCHEDULE.

Still worth doing

Diffing the two images should isolate exactly what the CB/BD split changes — we know the wire protocol is not it, and the flags byte (0xC5 vs 0x03) gives a concrete anchor to search for.

SUB 0x5A — bulk download. It streams the .IDFW file verbatim.

The complete read path works with no Instantel software in the loop.

It needs no arming sequence

Series III ignores a 5A probe unless preceded by 1E → 0A → 1E(token 0xFE) → 0C → 1F(token 0xFE) → POLL × 3. The Micromate answers a bare 5A request with nothing before it. That whole ritual is gone.

The offset word is a LENGTH, not a position

This is the key divergence. Series III walks chunks by absolute flash address, stepping 0x0200 per request. On the Micromate the offset word requests how much to send:

offset_word = 0x1000 + 2 × pages        pages = ceil(event_size / 512)

offset_word	pages	destuffed file bytes
0x1002	1	518
0x1004	2	1,030
0x1006	3	1,541
0x102C	22	11,033 — the whole event

event_size comes from the chain walk (the 4 bytes after the key in 1E/1F). One request returns the entire event; there is no chunk loop, no STRT end-offset parsing, and no TERM frame. Over-requesting is safe — 0x1030 (24 pages) returned exactly the same bytes as 0x102C, so the device caps at the real size.

Params are the Series III probe form: [0x00][key4][6 × 0x00].

The payload is the .IDFW file, byte for byte

[18-byte frame header] [ .IDFW file ] [chk] [ETX]     ← raw wire
                        ^ destuffed offset 16

The file begins 00 12 01 00 00 00 "Instantel\0" — _THOR_PREFIX + _INSTANTEL_TAG from micromate/idf_file.py. The first 32 bytes are identical to a production .IDFW pulled from the store.

⚠ Responses are DLE-stuffed. Destuff before locating the file, or the raw byte count overshoots (11,781 raw → 11,049 destuffed for an 11,032-byte event).

End-to-end proof

Event 055d4a82 downloaded over USB and fed straight to read_idf_file():

serial     UM12947
timestamp  2026-09-23 16:33:19
samples    Tran 3072   Vert 3072   Long 3072   MicL 3072
peaks      Tran 0.2433   Vert 1.3706   Long 0.2672  in/s

All four channels equal length, and the timestamp matches the 0x0C record for the same key. Independent cross-check: 0x0C reports a stored peak of 1.3720 for this event; the decoded samples give 1.3706 — two unrelated paths agreeing to 0.1%.

Consequence: no new codec work is needed. The bytes off the wire are the same bytes thor-watcher forwards today, so /db/import/idf_file ingests a directly-downloaded event unchanged. Everything the IDF decoder already does per-sample-exact applies.

What a full read now looks like

1E                     → first key + size
  0C(key)              → project/client/operator, timestamp, peaks
  5A(key, 0x1000+2×ceil(size/512))  → the whole .IDFW
1F                     → next key + size   (until null sentinel)

Setups are FILES, not a config block

Series III has one compliance config you overwrite. Series IV keeps named setup files on an on-device filesystem, with a pointer to the current one. From the firmware:

csetup.MMB              the current setup
factory.MMB             Factory Default Setup File
callhome.MMB            call-home config is a file too
"Current Setup File:  "         "Can Not Delete Active Setup File"
GetSelectedSetupFilePathName()  CSelectSetupFiles  CSaveSetupFile

Names are up to 20 characters and may contain spaces, hyphens, underscores. The unit's help text describes selecting, renaming and deleting them, and the event list records which setup file produced each event.

Filesystem primitives exist internally (NS_ReadFile_internal, NS_WriteFile_internal, NS_SeekFile_internal), but no generic file-transfer command is exposed on the wire — the only file-transfer string is CMD_STOP_CALLHOME_FILETRANSFER. So setups are unlikely to be pushed as raw .MMB blobs over the protocol.

SUB 0x1A reads the whole active setup — 2,092 bytes

Structurally close to Series III's ~2,126-byte compliance block, and it carries everything a setup consists of:

• the setup file name — Univ of Pitt-1st Yr. Housing-Loc1 Ruskin.MMB
• all four title note/value pairs — Location, Client, Company, General Notes, with their strings
• the sensor location string (Loc 1)
• per-channel labels and units: Tran in./s., Vert in./s., Long in./s., Mic psi (L), LMic psi (L), SMic (A)

Note LMic / SMic — linear and sound-level microphone variants that Series III does not have.

This is the read half of setup management, and it means a setup can be round-tripped: read the active config, modify, write it back. The write half is not yet attempted.

Static analysis of the firmware (2026-09-23, solo session)

Architecture

ColdFire / 68K, big-endian, Freescale MQX RTOS — not ARM as the vector table first suggested. The giveaway is the function epilogue/prologue 4E 5E 4E 75 4E 56 = UNLK A6 / RTS / LINK A6, littered through both images, plus an MQX_OK assertion string.

CB vs BD: the same source, ~10 lines apart

A byte diff is useless — 68% of bytes differ because the two are separately linked builds with everything relocated. A string-set diff is position-independent and tells the real story: 17,128 strings shared, and almost every "unique" string is the same message with a different source line number:

CB:  MONITOR[3268]: STATUS_BATTERY_LOW
BD:  MONITOR[3258]: STATUS_BATTERY_LOW      ← consistently 10 lines apart

The offset is exactly 10 across STATUS_BATTERY_LOW, STATUS_BATTERY_CRITICAL, Battery Critical Exit Monitor, histogram interval size of 0 and Offsets by channel — so one ~10-line block differs in the monitor module and essentially nothing else. The only functional string unique to either build is CITIZEN (a receipt-printer brand) in BD.

This corroborates the bench A/B from the other direction: the CB/BD split is a tiny code delta, not two protocol stacks. Whatever drives Instantel to ship two downloads, it is not a different wire protocol.

⚠ The SUB dispatch is a 68K switch jump table (CMPI.L bounds check → MOVE.W (table,PC,Dn) → JMP (d8,PC,Xn)). Byte-pattern hunting will not isolate the write opcodes — that needs a real disassembler.

Call-home config field names, from the firmware's own debug dump

CallHome.Enable               = %s
CallHome.DialString           = "%s"
CallHome.Retries              = %d
CallHome.SessionTimeout       = %d
CallHome.WaitForConnection    = %d
CallHome.WarmupTime           = %d
CallHome.PowerSave            = %s

Seven fields, which is what the 126-byte SUB 0x2C block has to encode. Note SessionTimeout and PowerSave have no Series III equivalent, and Series III's scheduled-time fields (time1/time2 hour/min) are absent here — consistent with Series IV moving scheduling into the THOR-downloaded scheduler instead.

Also present: AT+CSQ (signal quality), so the firmware talks AT to the modem directly.

All five bench events, downloaded and decoded

Read-only, over USB, no Instantel software:

key	declared size	got	decoded
055d4a81	4,076	4,076	histogram, 1 interval, 16:33:16
055d4a82	11,032	11,032	waveform, 3072 × 4 ch, 16:33:19
055d4a83	11,502	11,502	waveform, 3072 × 4 ch, 16:33:27
055d4a84	13,424	13,424	waveform, 3072 × 4 ch, 16:33:34
055d4a85	8,746	8,746	waveform, 2048 × 4 ch, 16:33:36

Every event arrived at exactly its declared size, every channel came out equal length, and the timestamps are sequential across the recording session.

⚠ Gap: no content-based record-type discriminator

read_idf_file() decides waveform vs histogram from the filename suffix (.IDFH / .IDFW) — and there is no filename when downloading over the wire. The first 64 bytes of a histogram and a waveform are byte-identical, so the header does not obviously carry the type either.

The protocol does supply one: SUB 0x0A returns length 0x1E for a histogram and 0x00 for a waveform (see the event-chain section). Any direct-download implementation must carry the type from the chain walk rather than inferring it from the payload, or find the type field inside the IDF header.

⚠ Unresolved: the 0x0C peak float

The float32 extracted from 0x0C runs 2–5% above max(Tran, Vert, Long) from the decoded samples:

key	0x0C float	max channel
…81	3.5152	3.4419
…82	1.3720	1.3706
…83	2.3542	2.2227
…84	3.5152	3.4419
…85	0.4227	0.4198

It is not peak vector sum either (computed PVS runs higher than both). The field may not be the peak at all — its offset was inferred from a byte marker, not established. Do not rely on it until it is pinned properly.

Worth noting the histogram (…81) and the loudest waveform (…84) report identical peaks to four decimals, in both measures. That is self-consistent: the histogram's single 1-minute interval spans the whole thumping session, so its maximum should equal the loudest event in it.

⚠ Untested and unsafe-until-agreed

Nothing below has been sent to a unit, and nothing should be without an explicit decision:

• Writes (0x68–0x83), call-home write (0x7E/0x7F)
• Erase (0xA3 / 0xA2)
• Start / stop monitoring (0x96 / 0x97)
• 0x1F (advance event pointer) — non-destructive on Series III but it does move device state, so it is parked with the rest

Also unknown:

• Whether 0x10 bytes inside request params need stuffing
• Everything about the call-home session — the device-initiated direction has not been observed at all. Specifically: how a unit announces itself, and how it learns an event was accepted so it stops re-sending it. That last question gates any homebrew receiver and cannot be answered over USB.

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Session provenance

Unit UM12947, firmware 11.0CB (Blastware line), on the bench via USB, zero events stored (memory free == total). Read commands only. Every response in this document was checksum-validated.

⚠ Firmware is the single biggest caveat on this document. Every finding here is from one unit on the Blastware build. A 11.0BD unit has not been touched.

An empty unit is a real limitation: 0x08, 0x1E, 0x0A and 0x06 all have event-dependent payloads that could not be exercised. Recording a couple of events on the bench unit would unlock the entire event-walk half of the protocol.