currently I am trying to bring up my custom i.MX6 DL board. DDR3 calibration worked fine and the stress test did not show any errors in several hours.
Afterwards I modified BOOTMODE and BOOTCFG settings to boot from SD-Card (uSDHC2), put in an SD-Card with a yocto-image on it and powered up. The processor accesses the SD-Card (I can see the lines toggle on the oscilloscope) but then falls back to "serial downloader boot mode".
Can someone give me a hint if there is way to investigate this issue other than "watching" the lines with a logic analyser...?
Does i.MX6 output something on any UART during its boot sequence?
Quite unlikely, but is it perhaps possible to debug this initial boot sequence (I have a J-Link available)?