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

Sibling to [instantel_protocol_reference.md](instantel_protocol_reference.md)
(Series III, "the Rosetta Stone") and
[idf_protocol_reference.md](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**.

---

## The headline

**The Micromate 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 from a Micromate.  Ten Series III read
commands were then tried and **all ten answered**, every one obeying the
Series III response-SUB rule.

This is not a new protocol.  It is close enough to Series III that large parts
of `minimateplus/protocol.py` may apply more or less directly, and the work
ahead is mapping *divergence* rather than mapping from scratch.

---

## 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.

---

## 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

```python
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**, at `payload[9]`:

| 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 | `0x2C` | — |
| `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.

---

## 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.

---

## 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]`.
5. **Modem serial rate is 115200**, not 38400 (per TMI provisioning practice;
   not independently verified here).

---

## ⚠ 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
- Whether the bulk waveform stream (`5A` on Series III) exists here, and
  whether it is the transport for `.IDFW` bodies we already decode
- 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.

---

## Session provenance

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

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.