Wiring & Power¶

How the Mote electronics connect. Everything runs from a single USB-C power bank at 5 V (see the 5 V-only rationale). Device names in the launch stack (/dev/mote_*) are created by the udev rules in mote_bringup/udev/.

Every data link is plain USB (standard male plugs into the device ports), so there's no special connector wiring — just the cables in the BOM. A few electrical details still want bench confirmation; those are marked Verify.

Diagram¶

flowchart LR
  BANK["UGREEN 140W power bank"]
  BANK -->|"Out1 high-current · USB-C to DC barrel · 5V"| MCB["Waveshare Serial Bus<br/>Servo Driver Board"]
  BANK -->|"Out2 · USB-C to USB-C · 5V"| PI["Raspberry Pi 5"]

  MCB ==>|"3-pin bus: 5V + serial"| SL["Left STS3215<br/>ID 7, inverted"]
  MCB ==>|"3-pin bus: 5V + serial"| SR["Right STS3215<br/>ID 9"]

  MCB -->|"USB serial to /dev/mote_servos"| PI
  LIDAR["RPLIDAR C1"] -->|"USB to /dev/mote_lidar"| PI
  CAM["USB webcam"] -->|"USB to /dev/mote_camera"| PI
  IMU["BNO085 IMU<br/>in testing"] -.->|"I2C to GPIO"| PI

  classDef power fill:#cde,stroke:#369;
  class BANK,MCB,PI power;

Solid lines = power and/or wired data. The lidar, camera and IMU are powered by the Pi over their data connection (USB / GPIO), not from the bank directly.

Connections¶

Power¶

From (port)	Cable	To	Carries
Bank Out1 (100 W USB-C)	USB-C → DC 5.5×2.1 mm barrel, 5 V	Servo board DC input	5 V
Bank Out2 (45 W USB-C)	USB-C ↔ USB-C, 0.3 m	Pi 5 USB-C power in	5 V
Servo board	3-pin servo lead	Left STS3215 (ID 7)	5 V
Servo board	3-pin servo lead	Right STS3215 (ID 9)	5 V

Data¶

From	Cable	To	Device node	Notes
Servo board (USB-C data)	USB-A ↔ USB-C, 0.3 m	Pi USB-A	`/dev/mote_servos`	CH343 USB-serial, 1 Mbaud
RPLIDAR C1	USB (cable supplied with unit)	Pi USB-A	`/dev/mote_lidar`	460800 baud; powered over USB
USB webcam	USB-A (captive)	Pi USB-A	`/dev/mote_camera`	UVC; powered over USB

The Pi 5 has 4 USB ports (2× USB-3, 2× USB-2). Servo board, lidar and camera take three of them.

Power notes (the fiddly bit)¶

Three things make the 5 V budget non-obvious:

Servos run at 5 V The STS3215's datasheet operating range is 4 V - 7.4V, with the expected value of 6V or 7.4V. Mote feeds the servo board 5 V and this seems to work well. Just don't expect the datasheet torque numbers, since those are quoted at the higher voltage.
A "100 W" USB-C port is not 100 W at 5 V. USB-C PD allows devices to negotiate different voltage/current depending on need. Focusing on 5V, the spec allows requesting up to 3A, however it is common for supplies to allow up to 5A. The Pi explicitly requests 5V/5A = 25W. The servos only need 500mA.

Rough 5 V budget¶

Load	Rail	Typical	Peak	Fed from
Raspberry Pi 5	5 V	5–10 W	25 W (5 V/5 A)	Out2
2× STS3215 (driving)	5 V via board	1-2 W (130mA no load)	10W (2A stall)	Out1
RPLIDAR C1	5 V via Pi USB	1.15 W (230 mA)	—	Pi
USB webcam	5 V via Pi USB	~0.5–1 W	—	Pi