lytedev/atorch-ud18-bt
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Daniel Flanagan d9cc167191 ud18: Atorch UD18 BLE logger (scan/log/CSV) + protocol notes 
Extracted from the cyberdeck repo. Verified live against the meter;
display cross-check pins current scaling at /100 with 10mA BLE
granularity (display resolves finer).
2026-07-13 11:55:07 -05:00
README.md ud18: Atorch UD18 BLE logger (scan/log/CSV) + protocol notes 2026-07-13 11:55:07 -05:00
ud18.py ud18: Atorch UD18 BLE logger (scan/log/CSV) + protocol notes 2026-07-13 11:55:07 -05:00

README.md

atorch-ud18-bt

Bluetooth LE logger/CLI for the Atorch UD18 (HiDANCE) USB power meter. Connects to the meter's UD18_BLE advertisement, subscribes to its report notifications, decodes them, and prints/logs CSV — handy for unattended bench power measurements (suspend drains, idle floors, charge curves).

Usage

Needs Python 3 + bleak. On NixOS:

nix-shell -p "python3.withPackages (p: [p.bleak])" --run "python3 ud18.py scan"
nix-shell -p "python3.withPackages (p: [p.bleak])" --run \
  "python3 ud18.py log --seconds 60 --csv run.csv"
  • scan — find the meter (prefers UD18_BLE; ignores the UD18_SPP classic-Bluetooth shadow advertisement, which BLE can't connect to).
  • log [--seconds N] [--csv FILE] [--address MAC] — stream reports (~1 Hz): epoch,V,A,W,Wh,Dplus,Dminus,tempC. --seconds 0 runs until Ctrl-C. Pass --address to skip the scan.

Protocol

Community-documented Atorch BLE protocol (no reverse engineering needed — see syssi/esphome-atorch-dl24 docs/protocol-design.md):

  • GATT service 0xFFE0, characteristic 0xFFE1 (notify)
  • 32-byte report frames: magic FF 55, message type 01, device type 03 (USB meter), big-endian fields: voltage ×0.01 V @0x04(3B) · current @0x07(3B) · capacity ×0.001 Ah @0x0A(3B) · energy ×0.01 Wh @0x0D(4B) · D− ×0.01 V @0x11(2B) · D+ ×0.01 V @0x13(2B) · temp °C @0x15(2B) · runtime h/m/s @0x17 · checksum @0x1C

Caveats

  • Current granularity: the BLE report steps in 10 mA units (/100 scaling confirmed by display cross-check: display 0.03294 A -> BLE raw 3 -> 0.030 A). The meter's own display resolves far finer (0.01 mA digits) -- use BLE logs for trends/loads >20 mA; read the display for single-digit-mA floors.
  • The UD18 measures D+/D− voltages but (at least on some port paths) does not pass USB data through — treat it as a power-only inline meter and verify your unit's port pairs if you need passthrough.
  • Checksum is parsed-past, not verified (XOR-0x44 scheme per the protocol doc) — readings at 1 Hz over a desk are not exactly hostile RF territory.