•
Secure:
firmware files are published on the QRP Labs website and are encrypted using
256-bit AES encryption technology
Selecting firmware update, then pressing the Y key proceeds with putting the U4B into bootloader
mode. You must then remove the power, and re-apply power; when power is applied in bootloader
mode, the U4B onboard LED will flash steadily.
To get back to normal operating mode, again cycle the power; on the next power-up, the U4B will
be in normal operating mode.
USB Flash memory stick emulation:
In the firmware update mode, the U4B pretends to be a USB Flash memory stick, having a
4MByte capacity and implementing a FAT16 file system. This virtual “Flash stick” contains two
files:
1.
the firmware program file of the U4B microcontroller. You may read the file from U4B, or
write a new one, just by dragging files in your file manager application. When you copy in a
new firmware file, U4B decrypts it and installs it. You will then need to cycle the power to
boot up again in normal operating mode.
2.
EEPROM (disk image) contents: the entire contents of the U4B disk (not individual files).
This is useful for creating a backup, so that during your development work you can get
back to a normal state easily. Again, you can read the file from U4B or write a new one to
U4B, simply by dragging files in your file manager application.
On entering the Firmware update procedure, a pop-up window should appear on your PC. On my
system (Linux XUbuntu 18.04) it looks like this:
U4B operating manual Rev 1.00
19
