Linux F20 & X20 UART Interface Troubleshooting – u-blox Services

This article provides troubleshooting guidance for Linux systems where UART interfaces are not automatically exposed for u-blox F20 and X20 products. These steps may be required before performing firmware updates using the Linux Firmware Update Tool.

Symptoms

The X20 or F20 receiver is detected over USB, but the UART interfaces are not available under:

/dev/ttyUSB*

Firmware updates performed over the native USB GNSS receiver interface may fail during USB re-enumeration. In these cases, updating over UART1 is recommended.

Verify Available UART Interfaces

Check whether the UART interfaces are already available:

ls -l /dev/serial/by-id/

Example output:

/dev/serial/by-id/usb-u-blox_AG_X20P_UART1_-if00-port0
/dev/serial/by-id/usb-u-blox_AG_X20P_UART2_-if00-port0

Alternatively:

ls /dev/ttyUSB*

If the UART interfaces are already visible, no additional configuration is required.

Identify the Device Attributes

If the UART interfaces are not available, identify the USB device attributes:

udevadm info --attribute-walk --name=/dev/ttyUSB3

Replace /dev/ttyUSB3 with the appropriate device on your system.

Create the Registration Script

Create the following script:

sudo nano /usr/local/bin/register-ftdi-uart.sh

Add the following contents:

#!/bin/bash

# Load the FTDI driver
modprobe ftdi_sio

# Register the custom u-blox VID/PID
echo 1546 050c  /sys/bus/usb-serial/drivers/ftdi_sio/new_id

# Trigger udev to bind the device
udevadm trigger --subsystem-match=usb-serial

Make the script executable:

sudo chmod +x /usr/local/bin/register-ftdi-uart.sh

Create the Systemd Service

Create the following service:

sudo nano /etc/systemd/system/FTDI_UART.service

Add the following contents:

[Unit]
Description=Register custom FTDI VID/PID for GNSS EVK
DefaultDependencies=no
Before=systemd-udevd.service
After=systemd-modules-load.service

[Service]
Type=oneshot
ExecStart=/usr/local/bin/register-ftdi-uart.sh
RemainAfterExit=true

[Install]
WantedBy=sysinit.target

Enable the Service

sudo systemctl daemon-reload
sudo systemctl enable FTDI_UART.service
sudo systemctl start FTDI_UART.service

Verify UART Availability

Confirm that the UART interfaces are now available:

ls -l /dev/serial/by-id/