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U-Boot console UART selection:
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The U-Boot port for this congatec board currently supports two different
configurations (defconfig files). The only difference is the UART that
is used as the U-Boot console UART. The default defconfig file:

conga-qeval20-qa3-e3845_defconfig

provides this console on the UART0 which is provided via a Winbond
Super-IO chip connected on the congatec Qseven 2.0 evaluation carrier
board (conga-QEVAL). This UART is the one provided with a SubD9
connector on the mainboard (the low one). The 2nd defconfig file:

conga-qeval20-qa3-e3845-internal-uart_defconfig

provides the U-Boot console on the BayTrail internal legacy UART,
which is routed from the QSeven SoM to the X300 connector on the
baseboard. Here is called COM2. The baseboard already provides the
RS232 level shifters. So a TTL-USB UART adapter does not work in
this case. The signals need to get connected directly to the
RS232 level signals of the PC UART via some adapter cable.