Arduino Uno - blank terminal

[balk77]

I am trying to load a-culfw on an Arduino Uno (on a Linux/Ubuntu machine) but when I approach the Arduino with screen /dev/ttyACM1 I get a blank screen. It does not respond to 'V' for version or anything. I also tried another terminal emulator

I've tried

• CUL-Arduino with different settings in flash.sh (MCU=m328p)
• miniCUL
• nanoCUL

In all three cases I've used BAUD=115200 because at lower speed I am getting
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 10 of 10: not in sync: resp=0x00

avrdude is running fine and uploading the hex file to the Arduino. The command
avrdude -p atmega328p -c arduino -P /dev/ttyACM1 -b 115200 -D -Uflash:w:./nanoCUL868.hex:i was running fine:
Reading | ################################################## | 100% 1.93s
avrdude: verifying ...
avrdude: 14708 bytes of flash verified

I've tried with and without the CC1101 868 board connected.
I've also tried to upload an example program via the Arduino IDE and that also worked fine.

update:
I've created a hex from an example script in the Arduino IDE (ASCIITable.ino) and loaded it via 'avrdude -p atmega328p -c arduino -P /dev/ttyACM1 -b 115200 -D -Uflash:w:./ASCIITable.ino.standard.hex:i'
'screen /dev/ttyACM1' gives the expected output. This means that avrdude, screen and the Arduino are working fine. It must be something in the code for my specific device. Any help would be appreciated 👍