OpenMower — Open Source RTK GPS Robotic Mower – Prepare the Parts

Docs: Step 2.1: Prepare the GPS

Mon, 01 Jan 0001 00:00:00 +0000

Update Firmware and configure the GPS board

Info

<p>There is a tutorial video available for this step of the process! <br/>

Check my YouTube video here: Video

(time 16:21 - 17:15)

Prerequisites

An Ardusimple F9P GPS board
A Micro USB Cable
A Windows PC
Latest v1 version of the u-center software:
🔗 https://www.u-blox.com/en/product/u-center
Don’t get u-center V2, you will need u-center v1 for the F9P.
The GPS configuration file
🔗 robot-fw-1_51.txt
This will open in a new browser tab. Use Ctrl+S to download the file.

Step 2.1.0: Update Firmware

Warning

<p>The F9P now exists in multiple variants. The firmware below is for the L1 + L2 version. Make sure that on the u-blox chip, it says one of the following: <strong>ZED-F9P-02B, ZED-F9P-04B or ZED-F9P-05B!</strong>.</p>

If it’s a different board, don’t use the linked firmware, get it from u-blox.com directly.

Update the firmware of your Ardusimple board to version ZED-F9P HPG 1.51 - link here . There’s a guide on the Ardusimple Website .

Step 2.1.1: Open u-center and connect to your GPS

After installing u-center, connect your Ardusimple board using the “Power+GPS” USB socket to your Windows computer. You should see the blue LEDs of the board come on and Windows should recognize the device as a COM port. With the module connected to your PC, open the u-center software.

In u-center, first connect to your board by selecting the appropriate COM port in the Receiver -> Connection menu.

Step 2.1.2: Transfer the configuration to the GPS

After successfully connecting to the board, you can transfer the previously downloaded configuration file robot-fw-1_51.txt by opening the window Tools -> Receiver Configuration .... In this window you open the robot-fw-1_51.txt using the ... button and then transfer the configuration to the GPS by clicking the Transfer File -> GNSS button.

Step 2.1.3: Save configuration to Flash

In order to keep the GPS configured even after powering it down, you need to save the current configuration to Flash memory. In order to do this, select View -> Configuration View. In the new window you need to select CFG (Configuration) in the list on the left side and then enable Save current configuration. Make sure that 0 - BBR and 1 - FLASH are both selected on the right side of the window. Once that’s done, click the Send button in the lower toolbar of the window.

Once successful, there will be a timer showing on the upper right side of the window. This is the timer since the last message was sent to your GPS board. It should be 0s directly after clicking Send.

Step 2.1.4: Done 🎉

Your GPS is now configured for use with the Open Mower software. You can disconnect it from your Windows PC.

Connect your UM9xx to your PC using the supplied USB-C cable
Open a serial terminal (minicom, miniterm, CuteCom, etc.) at 115200 baud
Take attention that your line-end termination has to be CR/LF
Send CONFIG↵ Enter to verify the connection. You should see readable key/value style output. If not, check cable, port, and permissions.
Reset and switch the baud rate to 921600 by entering the following commands, line by line:

FRESET↵ Enter
CONFIG COM1 921600↵ Enter

(After FRESET the module may take a few seconds to respond.)
Re-check connection with the simple CONFIG command. If you don’t get similar results than before, change your serial terminal speed to 921600 baud (re-open if necessary) and run CONFIG again, till your get a reasonable response
Apply the rover configuration by entering the following commands, line by line:

MODE ROVER UAV↵ Enter
GPGSV COM1 2↵ Enter
GPRMC COM1 1↵ Enter
GPGSA COM1 1↵ Enter
GPVTG COM1 1↵ Enter
GPGST COM1 1↵ Enter
GPGGA COM1 0.2↵ Enter
SAVECONFIG↵ Enter

Take attention to the SAVECONFIG command, which stores settings so they survive power cycles.
Unplug the USB cable from the UM9x module and mount it to the CarrierBoard (solder required headers first if required).

Continue with Step 2.2: Prepare the SD Card

Docs: Step 2.2: Prepare the SD Card

Mon, 01 Jan 0001 00:00:00 +0000

We have created a Raspberry Pi image which is modified specifically for Open Mower use. The modifications include:

Networking setup for the robot’s internal network
A hotspot to make it easy to connect the robot to your home network
Docker installation for easy container management
Browser based terminal access to the robot
… and more!

In this step, we flash the image and do some basic setup for your mower.

Info

This guide is for the Lite version of the Raspberry Pi Compute module (the version without eMMC storage).

If you have a compute module with eMMC, you can safely skip this step for now and continue with preparing the mainboard.

You can flash the CM4, once your mower is powered up. Here is the guide on how to do it

Prerequisites

In order to follow this guide, you will need:

Raspberry Pi CM4 Lite (no on-board memory)
Micro SD card with at least 16 GB
A PC with the Raspberry Pi Imager Software installed:
🔗 https://www.raspberrypi.com/software/
The latest OpenMowerOS Image:
🔗 https://github.com/ClemensElflein/OpenMowerOS/releases
You can download it in the Assets section. You don’t need to unpack the image.
An SD card reader

Flash the Image to your SD Card

Start the Raspberry Pi Imager Software.
Select Raspberry Pi 4. Click Next to continue.
Then click Use Custom to open the image file you downloaded earlier. Click Next to continue.
Select your SD card from the Window. Make sure that you are really selecting the correct SD card, all data on the selected device will be erased!. Click Next to continue.
Check that everything is correct and click WRITE. You will be prompted to confirm once again, you might be prompted to enter your admin password.
Wait for the process to finish.

Configuring the Image

Older versions of the Raspberry Pi Imager software allowed the image to be configured directly in the software. In the current version, this is no longer possible.

When using an older version of the Raspberry Pi Imager, you can still configure the image as usual, but renaming the user is not possible. The user will always be named openmower.

Done 🎉

You can now remove the SD card from your PC, it is ready to be used with the Open Mower software. Set it aside and continue with preparing the mainboard. .

Docs: Step 2.3: Prepare the Mainboard

Mon, 01 Jan 0001 00:00:00 +0000

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

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

Align the CM4 with the xCore board as shown in the picture.
Place two fingers over the connectors of the xCore and the CM4.
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)

Info

This step is different, depending on which heat sink you are using. The images here show the Berry Base heat sink, but the process is similar for other heat sink models as well.

Make sure to use spacers between the PCBs, otherwise the screws will put excessive pressure onto the connectors.

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

Mount the spacers to the heat sink as shown in the picture.
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!
Align the heat sink with the CM4 as shown in the picture.
Fix the heat sink with the two screws on the bottom. Do not fix the upper two holes.
Press the 3d printed spacer between the CM4 and the xCore board as shown in the picture.
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.

Info

Before finishing this step, make sure that your SD card is inserted into the CM4 (if using the version with eMMC, skip this step). Depending on the mainboard layout, you won’t have easy access to the SD card slot later.

Follow these steps to insert the xCore into the mainboard:

Insert the xCore board into the slot on the mainboard. It is approximately a 45 degree angle.
Push the board down until it is flat with the mainboard. Make sure the arms on the side engage with the xCore.
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 .