2.
Terminal connection
The U4B tracker contains a Virtual COM Serial port USB device, for accessing QDOS (QRP Labs
Disk Operating System) via a terminal emulator program running on your PC. This connection is
used for initial configuration, and all BASIC programming, development and testing that you may
wish to do, if you are pursuing more advanced flight goals. A common USB-A to USB-micro cable
is required. Any OS may be used (Windows, Linux, Mac etc).
2.1 Drivers and PC setup
No additional drivers are required for operation with most Linux distributions, Apple Mac, MS
Windows 10 or 11.
For older versions of MS Windows, it may be necessary to install a driver for the serial port
because this driver is not on your computer already by default. This driver is available from the ST
Semiconductor website at https://www.st.com/en/development-tools/stsw-stm32102.html and is
applicable to 98SE, 2000, XP, Vista®, 7, and 8.x Operating Systems. There is a description for
installation on Windows 7/8 on the QRP Labs QLG2 page http://qrp-labs.com/qlg2 so if in doubt,
please check this.
Linux special note
On Linux systems, a particular problem can occur. When the QDX Virtual COM (Serial) connection
is detected, the PC thinks that a modem has been connected and starts trying to send it Hayes
AT-commands dating back to 1981, implemented on Hayes’ 300-baud modem. Yes! 40 years
ago…
The Operating System attempting to send AT commands to your QDX will certainly mess
everything up. Not least because when QDX receives a carriage return character, it will enter
Terminal Applications mode; this will send all sorts of characters back to the PC (as QDX thinks it
is now talking to a terminal emulator) and it will disable CAT command processing, so your PC digi
modes software will not be able to talk to QDX. Disaster.
To fix this you need to issue the following commands to disable ModemManager:
sudo systemctl stop ModemManager
sudo systemctl disable ModemManager
sudo systemctl mask ModemManager
This will permanently stop ModemManager. If for some reason, you actually DO need
ModemManager operational, for some other reason… well there IS a way to stop it just for QDX…
but Google will be your elmer on this!
2.2 PC terminal emulator
I use Linux (XUbuntu 18.04) and I’m using the PuTTY terminal emulator. There are numerous
other terminal applications which will work fine. You may have your own favourite. They are all
capable of correct operation with U4B.
I start PuTTY using command line “sudo putty” then connect to U4B on /dev/ttyACM0 (or ACM1,
ACM2 etc if ACM0 is already in use by another device). On Windows operating system it will be a
COM port numbered for example, COM1. It is necessary to know which serial port is being used
U4B operating manual Rev 1.00
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