dgm20-linux/PROTOCOL.md

DGM20 control protocol

These notes come from Maono Link 4.0.88 for Windows. The app loads a per-model plugin, and the plugin for USB 352f:0105 is DGM20_OLD.dll. Every value below was checked against a real mic (firmware 2.1.2) unless it is marked otherwise.

Transport

The mic has USB audio interfaces 0-2 and a HID interface 3. Interface 3 carries a vendor usage page (0xFF01) with four reports:

report	direction	size
0x50	out	15
0x51	out	63
0x10	in	15
0x11	in	63

The app uses only 0x51 (requests) and 0x11 (replies). On Linux the interface is a hidraw node: a 65-byte write() (the report id plus 64 data bytes) sends a request, and read() returns replies.

Packet

offset  size  field
0       1     report id: 0x51 request, 0x11 reply
1       1     0xC4
2       1     length of bytes 1..end, including the checksum
3       2     0x0000
5       1     type
6       n     payload, u16 little-endian words
6+n     2     checksum, u16 LE = -(sum of bytes 1 .. 5+n)

The rest of the 64 bytes is zero-padded.

type	request payload	reply
2	(reply only)	write ack: status (0 = ok)
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.
4	addr	addr, value
5	addr, count, data...	bulk write. The app uses it only to write the serial number; don't.
6	addr, count	addr, count, values... (range read)

Registers

reg	meaning	values
0x0003	model name, 8 words, ASCII	"DGM20"
0x000B	firmware version, 3 words	2, 1, 2
0x001E	serial number, up to 20 words
0x1008	DFU mode (read)	0 = normal
0x100A	factory reset	write 1
0x2022	mute	0 / 1
0x2026	headphone monitoring	2000 = on, 3000 = off
0x2027	noise cancellation	0 / 1
0x2028	noise cancellation strength	0-100
0x202A	RGB ring brightness	0-100 (the app does not show it for this model)
0x202C	vocal enhancement	0 / 1
0x204B	level-meter enable	not answered by firmware 2.1.2

Maono Link reads settings once, in this order: 0x204B, then 0x2022, then a range read of 0x2027 (count 2), then 0x2026, then 0x202C. After that it relies on type-3 packets the mic sends on its own.

Present in the plugin but not used for this model

The DLL shares widgets with the PD200X plugin, so it contains EQ and RGB-colour code. That code is never instantiated for the DGM20, and the mic does not answer reads of these registers. They are listed here for anyone exploring.

• EQ: 5 parametric bands, each 5 words, starting at 0x204D + 5·i. The HPF is at 0x2066 and the LPF at 0x206B. Each band is [enable, type, freq Hz, gain dB×10+2000, Q×100].
• Light on/off: 0x2036. Colour index: 0x2038.