justinandClaude Opus 5.5
1fcf73ed9d
- Remove RGB brightness: firmware 2.1.2 stores the value but the LEDs never change, so the control did nothing. PROTOCOL.md notes why. - Lock the device per transaction (flock) so the CLI and the web service can't interleave and steal each other's replies. - Detect a mic that is plugged in but no longer answering and tell the user to replug it (a USB reset is not enough; settings survive). Seen when hardware buttons are held while settings are being written. - Web page keeps the last known value when a poll comes back partial, instead of drawing unanswered settings as off. - New screenshot. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
75 lines
3.0 KiB
Markdown
75 lines
3.0 KiB
Markdown
# DGM20 control protocol
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These notes come from Maono Link 4.0.88 for Windows. The app loads a per-model plugin, and the
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plugin for USB `352f:0105` is `DGM20_OLD.dll`. Every value below was checked against a real mic
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(firmware 2.1.2) unless it is marked otherwise.
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## Transport
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The mic has USB audio interfaces 0-2 and a HID interface 3. Interface 3 carries a vendor usage page
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(`0xFF01`) with four reports:
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| report | direction | size |
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|--------|-----------|------|
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| 0x50 | out | 15 |
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| 0x51 | out | 63 |
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| 0x10 | in | 15 |
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| 0x11 | in | 63 |
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The app uses only 0x51 (requests) and 0x11 (replies). On Linux the interface is a hidraw node: a
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65-byte `write()` (the report id plus 64 data bytes) sends a request, and `read()` returns replies.
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## Packet
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```
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offset size field
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0 1 report id: 0x51 request, 0x11 reply
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1 1 0xC4
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2 1 length of bytes 1..end, including the checksum
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3 2 0x0000
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5 1 type
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6 n payload, u16 little-endian words
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6+n 2 checksum, u16 LE = -(sum of bytes 1 .. 5+n)
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```
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The rest of the 64 bytes is zero-padded.
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| type | request payload | reply |
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|------|-----------------|-------|
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| 2 | (reply only) | write ack: `status` (0 = ok) |
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| 3 | `addr, value` pairs | type-2 ack. The mic also sends type-3 packets on its own when a setting changes on the hardware, such as the touch pad. |
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| 4 | `addr` | `addr, value` |
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| 5 | `addr, count, data...` | bulk write. The app uses it only to write the serial number; don't. |
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| 6 | `addr, count` | `addr, count, values...` (range read) |
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## Registers
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| reg | meaning | values |
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|--------|---------|--------|
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| 0x0003 | model name, 8 words, ASCII | `"DGM20"` |
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| 0x000B | firmware version, 3 words | `2, 1, 2` |
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| 0x001E | serial number, up to 20 words | |
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| 0x1008 | DFU mode (read) | 0 = normal |
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| 0x100A | factory reset | write 1 |
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| 0x2022 | mute | 0 / 1 |
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| 0x2026 | headphone monitoring | 2000 = on, 3000 = off |
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| 0x2027 | noise cancellation | 0 / 1 |
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| 0x2028 | noise cancellation strength | 0-100 |
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| 0x202A | labelled RGB ring brightness in the app's shared code | stores 0-100, but the LEDs do not change on firmware 2.1.2; not exposed |
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| 0x202C | vocal enhancement | 0 / 1 |
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| 0x204B | level-meter enable | not answered by firmware 2.1.2 |
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Maono Link reads settings once, in this order: 0x204B, then 0x2022, then a range read of 0x2027
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(count 2), then 0x2026, then 0x202C. After that it relies on type-3 packets the mic sends on its
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own.
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## Present in the plugin but not used for this model
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The DLL shares widgets with the PD200X plugin, so it contains EQ and RGB-colour code. That code
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is never instantiated for the DGM20, and the mic does not answer reads of these registers. They
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are listed here for anyone exploring.
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- **EQ:** 5 parametric bands, each 5 words, starting at 0x204D + 5·i. The HPF is at 0x2066 and the
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LPF at 0x206B. Each band is `[enable, type, freq Hz, gain dB×10+2000, Q×100]`.
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- **Light on/off:** 0x2036. **Colour index:** 0x2038.
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