Serial Console
According to udoo-bolt pinout complete pins for UART0 TX & RX are pins 36 & 34, GND being pin 31. Theses pins are located on the bottom row of embedded controller pinout more towards the bolts header pins. One can see early console text by utilizing a dumb/serial terminal emulation program like picocom/minicom.
sudo picocom -b 115200 /dev/ttyUSB0 # character device varies
