Rock64 Boot-up Bug with Serial Console Cable

The Rock64 often will not boot-up with a serial console connected to the console uart pins (6, 8, & 10).

Symptom:  lights come on, nothing happens at all.

Solution:  unplug the Tx line coming in on pin(10) prior to applying power for boot-up.

The Tx line often (if not always) has 3v3 on it when the other end is powered up, even in the idle state.  This voltage present on pin(10) of the Rock64 prevents it from booting, sadly.  I have reliably verified that unplugging the Tx line in on pin(10) of the Rock64 will allow the boot-up to start...  as it boots up , carefully plug the Tx line back onto pin(10).

Also noticed that the Tx line (if left connected to pin[10] on Rock64 power-down) will back-feed into the board, which will dimly light the red LED (small glow) !  This back-feed is preventing boot-up.

Fortunately the serial console monitor does not need this line connected to monitor as long as it has the Rx connection and a good ground,  so unplugging the line from pin(10) does not prevent monitoring the boot-up messages on the serial console.

Note:   This problem occurs on both of my boards;  dev board pre production, and the production master-piece which came last week !

Note:   At this point I don't know if the current draw on the Tx line might damage the monitor ; currently I'm using my PineA64 desk machine as the serial monitor for my Rock64 boards.

marcushh777    Cool

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Messages In This Thread
Rock64 Boot-up Bug with Serial Console Cable - by MarkHaysHarris777 - 08-24-2017, 04:33 PM

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