moving to same chip, different board: no console output

[David Picard <david.picard@clermont.in2p3.fr>]

Hello,

I am working on a project for which we selected an Intel/Altera Cyclone 
5 SoC FPGA (an FPGA with an ARM core). As the project evolves, I have to 
change boards and I am facing issues to boot: absolutely no output on 
the serial console (USB virtual COM port), not even from Barebox.

Previous working configuration:
- SD card image produced by Buildroot with Barebox as the bootloader
- Terasic ADC-SoC demo board, booting from the SD card.
https://www.terasic.com.tw/cgi-bin/page/archive.pl?Language=English&No=1061&PartNo=1

Current non-working configuration:
- Eclustra Mercury+ SA2 module, also with a Cyclone 5, plus SDRAM, RTC, 
QSPI flash, etc. I think that the main difference between both Cyclone 5 
chips is the size of the logic section is bigger on the module. The 
module has more RAM.
https://www.enclustra.com/en/products/system-on-chip-modules/mercury-sa2/
- Enclustra ST1 demo baseboard. It has a JTAG port, should this 
information be of interest.
https://www.enclustra.com/en/products/base-boards/mercury-st1/

I the current configuration, I get no output on the serial console.

What I did:
- I checked the hardware configuration (switches to select booting from 
the SD card and USB config) with a bare-metal application provided by 
Enclustra.
- I used Enclutra's .dts and .dtsi files, which differ very slightly 
from the Linux kernel tree files.
- I checked how the SD card is connected: to the exact same pins in both 
configurations.
- I had a look at Barebox menuconfig, but nothing caught my eye.

So, now I'm stuck, and I'm looking for some guidance.

David