Step 2.3: Prepare the Mainboard

Prerequisites

In order to follow this guide, you will need:

• An OpenMower v2 Mainboard
• 1x xCore Board
• 1x Raspberry Pi 4 CM4
• 3x xESC Motor Controllers
• 1x GPS Module
• Mounting Brackets for the xCore
• Optional: CM4 Heat Sink

Step 2.3.1: Mount the CM4 onto the xCore

If you are using a CM4 heat sink

Place the spacer on the lower two mounting holes of the CM4 as shown in the picture. Do not place spacers on the upper two holes:

The spacers I used are 1.7 mm thick and were provided with the heat sink.

If you are not using a CM4 heat sink, you can skip this step.

Mount the CM4 onto the xCore

• Step 1 - Align CM4
• Step 2 - Grab the CM4 at the connectors
• Step 3 - Press until you hear it click

The next step is to mount the CM4 onto the xCore. To do so:

1. Align the CM4 with the xCore board as shown in the picture.
2. Place two fingers over the connectors of the xCore and the CM4.
3. Gently press down until you hear and feel both connectors click.

Step 2.3.2: Mount CM4 Heat Sink

(optional - except for the spacers in the end)

• Step 1 - Mount spacers to heat sink
• Step 2 - Stick thermal pads onto the chips
• Step 3 - Align heat sink with mounting holes
• Step 4 - Fix the heat sink using the lower two screws
• Step 5 - Insert spacers on the upper holes
• Step 6 - Insert SD Card

The next step is to mount the heat sink onto the CM4. To do so:

1. Mount the spacers to the heat sink as shown in the picture.
2. Place all thermal pads onto the corresponding chips.
   Important: The pads have clear plastic cover on the top and glue on the bottom.
   Do not forget to remove the top plastic cover as well!
3. Align the heat sink with the CM4 as shown in the picture.
4. Fix the heat sink with the two screws on the bottom. Do not fix the upper two holes.
5. Press the 3d printed spacer between the CM4 and the xCore board as shown in the picture.
6. It is now a good time to insert the SD card into the CM4 (except for the version with eMMC).

Step 2.3.3: Insert the xCore into the Mainboard

Now that the xCore board is assembled, it is time to insert it into the mainboard.

• Step 1 - Insert xCore in 45 degree angle
• Step 2 - Lock the tabs on the left and right of the board
• Step 3 - fix the core using screws

Follow these steps to insert the xCore into the mainboard:

1. Insert the xCore board into the slot on the mainboard. It is approximately a 45 degree angle.
2. Push the board down until it is flat with the mainboard. Make sure the arms on the side engage with the xCore.
3. Use two screws to secure the xCore board to the mainboard. Don’t put spacers or anything, otherwise the mainboard will not fit into the mower (at least for the YardForce Classic 500).

Step 2.3.4: Insert xESCs and GPS into the Mainboard

Finally, we can insert the remaining modules into the mainboard.

Match the pins of the xESCs as well as the GPS board to the corresponding pins on the mainboard. Don’t worry if some of the ESC pins don’t have mating connectors, they are only used for initial firmware upload after the boards are manufactured.

The resulting board will look similar to this (example shows a YardForce mainboard):

Step 2.3.5: Done 🎉

You have now finished the preparation of the mainboard. You can now proceed with the mower-specific guide.