OpenMower — Open Source RTK GPS Robotic Mower – simplertk2b

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: Troubleshooting GPS-RTK

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

We assume that you at least followed documentation of GPS setup . If mower is already assembled - open the top cover.

Get your Windows PC and connect to GPS module directly with microUSB cable (as if you were uploading the configuration).

Make sure that Protocol of received messages in bottom status bar right shows UBX, not NMEA. If not - upload configuration again. Then disconnect/connect power of GPS and make sure it stayed UBX.

Connect the antenna to the board and go outside to check if general GPS is working. If the mower is already assembled and an antenna is plugged in - just take it outside with the mower. Even indoors next to the windows with antenna connected, you should see satellites and other info start appearing in u-center. In few minutes GPS Fix led will start blinking on GPS board.

Deviation map (View -> Deviation Map, F12) should stay in a ~1m, that what you expect from average GPS. If you got some existing garbage there already, clean it via File -> Database clean.

Now let’s connect NTRIP. We assume that you either found a suitable NTRIP node somewhere nearby (<30km) or running your own base station .

Go to Receiver -> NTRIP Client... and configure your NTRIP settings. This will be the same settings that you will use in the ROS configuration file later.

NTRIP client should display green connection in the status bar. Deviation map (View -> Deviation Map, F12) should stay dead center. No RTK led will start blinking or go away completely.

Test GPS on Mainboard

We have checked that GPS works alone, let’s see if it would together with the mainboard. Plug the GPS into the mainboard. Everything should light up and start flashing.
Wait until the LED lights up GREEN or GREEN/RED.

🔋 Powering the mainboard

If you don’t have dock station assembled and want to save the power in the main mower battery, you can power it from the Pico Dev board MicroUSB port, right below the GPS board. Use a 1A+ power bank, because computer USB port’s 500mA might be not enough.

OpenMowerOS version:
0.1.0

Then SSH into your OpenMower.
In the home directory (~/) there is a scripts called start_ros_bash.sh.
Run the start_ros_bash.sh script by executing ~/start_ros_bash.sh which should take you to a bash inside the container.

There you can run rostopic list to list all topics and rostopic echo --clear -w 5 /ll/position/gps to look at the GPS data.
You will get some lines of data:

header:
 seq: 44
 stamp:
 secs: 1708328554
 nsecs: 51810942
 frame_id: "gps"
sensor_stamp: 114172000
received_stamp: 1711341013
source: 1
flags: 3
orientation_valid: 0
motion_vector_valid: 1
position_accuracy: 0.024
orientation_accuracy: 3.141
pose:
 pose:
 position:
 x: 1.975
 y: 4.819
 z: 114.9
 orientation:
 x: 0.000
 y: 0.000
 z: 0.201
 w: 0.979
 covariance: [88.21, 0.000, 0.000, 0.000, 0.000, 0.000, 0.000, 88.21, 0.000, 0.000, 0.000, 0.000, 0.000, 0.000, 0.000, 88.21, 0.000, 0.000, 0.000, 0.000, 0.000, 10000, 0.000, 0.000, 0.000, 0.000, 0.000, 0.000, 10000, 0.000, 0.000, 0.000, 0.000, 0.000, 0.000, 9.869]
motion_vector:
 x: 0.045
 y: -0.05
 z: -0.01
vehicle_heading: 1.570
motion_heading: 0.405
---

The important lines here are:

flags: 3
you want a 3 here since that means your rtk state is “fixed”
3 is “fix”, 5 is “float” and 0 is “single” (classic non-rtk GNSS gps only)

position_accuracy: 0.024
this value is in meters so the example has a accuracy of ~2,5cm and that is great.
It can be the case that this value is ok but the rtk state is not yet “fixed”