5 🔌 Connect Wires

"Everything is connected." 🤝

5.1. Servo wiring

Connect the wires of servos to the NyBoard servo pins as below. They follow a circular symmetry. Notice the skipped pins between the head and leg servos. They are reserved for our future robots with more joints.

The black wire (GND wire) should be closer to the board.

Bottom view:

Insert the infrared receiver under the back plate so that the sensor can expose to the outside.

Make sure that the wires go into the body, bypass the columns, then plug into the servo pins. Arrange the wires so that they don't get in between the servo plugs and the body frame. NyBoard should be leveled on the four standoffs. Use four M2x8 self-tapping screws to fix the NyBoard.


5.2. Battery

Insert the battery's plug into NyBoard's anti-reverse power socket.

Hold the button of the battery for 3 seconds to power on the battery. If the LED on the battery lights red, recharge the battery until it turns green. The blue and orange “eyes” of the Petoi logo on NyBoard should light on.

5.3. Coarse tuning and installation

5.3.1. What is a servo's middle point?

The servos have a limited reachable angle range. We want to define a position in the middle of its range to allow sufficient working space for the servo.

After entering the calibration mode, the servos will rotate to the middle point we defined. However, when attaching the legs, they will be engaged to the servos' shaft through the servo arms. There’re 25 teeth on the P1S servo's output shaft, so each tooth corresponds to 14.4 degrees. You will have an inevitable installation offset of -7.2~7.2 degrees.

During this coarse installation stage, you only need to attach the legs close to 90 degrees, so that the absolute value of offset should be smaller than 7.2 degrees. We will fine-tune the joints in the later programming section.

We only coarse installed the legs for the pre-assembled Bittle kit. You still need to finetune it for the best performance.

5.3.2. Enter calibration mode

Before we attach the legs, the servos' output shafts should be at the calibration angle. After uploading the codes to NyBoard, you can enter the calibration mode to attach the legs and head to the body. There’re 2 ways to enter the calibration mode:

  • Press the “EQ” button on the IR remote controller (recommended during the assembling stage).

  • Send the “c” command through the UART serial interface (will be used in the fine-tuning stage).

Press the “EQ” key. The servos should rotate and stop at the calibration angles.

5.3.3. Attach the head

In the calibration mode, insert the output shaft of the head servo into the servo arm of the neck. Try your best to make the head point along the central axis.

Use an M2x4 flat head screw to lock the servo shaft and the servo arm from the bottom side of the chassis.

5.3.4. Attach the battery

The front of the battery is heavier with a Lithium core inside. Put the battery pack in the direction shown in the figure below. Align the mounting cap with the two large holes along the chassis' central track.

Press the battery down and slide it towards the head.

Organize the battery's cable. You may hide most of the cable within the body.

By sliding the battery in the track, or rotating its installation direction by 180 degrees, you can shift the center of mass towards the tail. The adjustment will counterweight the extensible gadgets you install on the head.

5.3.5. Attach the legs

Take one assembled upper leg and keep Bittle in the calibration mode (“EQ” key).

Attach the yellow side of the upper leg to the shoulder servo. Try to find the direction closest to the vertical angle. Don't rotate the servo during installation. Install the lower leg at a perpendicular angle to the upper leg.

You can use the included "L" shape tuner as a reference.

Attach all four groups of legs, and use the M2x4 screws to lock them.

5.3.6. Wire shield

There’re two snaps on both sides of the wire shield. Their relative height is different.

Flatting the wire of the lower leg to remove any coils. Then snap the wire shield to the upper leg.

The edge of the shield should be parallel to the surface of the upper leg.

Below shows the wrong installation configuration.

5.3.7. Body cover

The 6-pin female socket is used for connecting the programmer and communication dongles. Carefully bend it forward in a smooth arc if you are not going to attach a Raspberry Pi.

Attach the tail to the pin on the cover.

Snap the cover from one side of the body. Organize the wires so that they don't get stuck between the cover and the body. Then push the cover down to the other side of the body. You should hear a clear snap sound.