Nybble User Manual
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5 🔌 Connect Wires

"Everything is connected." 🤝

5.1. Joint map

Nybble's servos are connected to NyBoard's PWM pins symmetrically and resemble the nerves along the spinal cord. Though Nybble doesn't have shoulder roll DoF, those indexes(4~7) are reserved for the full OpenCat framework.
NyBoard V0_* and V1_* have different PWM pin orders, but the physical servo connection remains the same. All adjustments are handled in the software. You don't even need to read the pin numbers on the PCB board.
Use h for the head, t for the tail, r for shoulder roll joint, s for shoulder pitch joint, k for knee joint, F for the front, H for hind, L for left, R for right, the full joints map of OpenCat is:

5.2. Plug in the servos

Observe the indexing pattern to connect servos with correct PWM pins. Be careful with the wires’ direction. The brown wire of the servo is GND, while the GND on NyBoard V0_1 is along the centerline. In later versions of NyBoards, they are opposite.
A quick check is that all On NyBoard V0_1 the brown wires should be far away from the board surface. On NyBoard V0_2 the brown wires should be close to the board surface.
From NyBoard V0_2, the location of servo wires will still be the same, but their direction of colors will be opposite
Even though the PCB layouts vary on different NyBoards, the wiring pattern is the same. You don't need to read the indexes of the servo pins when plugging the servos. The joint mapping is done automatically in the OpenCat code. You just need to select the right board version when uploading the code.

5.3 Prepare for calibration

You must enter the calibration mode before installing the head and the legs. After entering the calibration state, you need to attach the head, tail, and leg components to the servo's output shaft. Don't screw them yet.
There are five methods to enter the calibration state:
  • Long-press the battery and boot up the robot with one side up. It will enter the calibration state automatically.
  • Use the mobile app Petoi and enter the calibration panel.
  • Use Joint Calibrator in Petoi Desktop App:
    • If you have already connected the robot and computer with a serial port, It will enter the calibration state after you click the "Joint Calibrator" button
    • Click the "Calibrate" button in the calibrator's interface
  • In the serial monitor of Arduino IDE, enter the serial command "c"
  • Press the calibrating button
    (3,3 - the 3rd row and 3rd column) on the infrared remote.
Install the head, tail and leg components as following picture:
You can install the legs with the reference of a triangle ruler or the L-shaped ruler included in the kit.

5.4 Wiring

After calibration, troubleshooting and final assembling, It’s time to think about wiring routes to make Nybble look neat. There are multiple slots on the frame designed as a wire organizer. Feel free to develop your own style for connecting future accessories. Make sure the wires don’t get in the way of the servos‘ movement.
Below are my wiring routes.
NyBoard alone
NyBoard with Raspberry Pi