03-21-2018, 11:46 AM
IT WORKED! THANK YOU GUYS SO MUCH!!! 
Indeed, shorting gpio pins 20 and 21 during start-up disabled the SPI flash, so I could manage to boot from mirco sd - which I prepared with ayufan's image for erasing the SPI flash. Only tricky thing was to find the right moment on which I had to stop shorting pins 20 & 21, so that the erase script could do it's work.
But now everything is fine and my rock64 boots from sd card like a charm. Yay!
Again: thank you for your quick and qualified help! This community is awesome!
...and now - I can start fiddling around with my sbc...
Indeed, shorting gpio pins 20 and 21 during start-up disabled the SPI flash, so I could manage to boot from mirco sd - which I prepared with ayufan's image for erasing the SPI flash. Only tricky thing was to find the right moment on which I had to stop shorting pins 20 & 21, so that the erase script could do it's work.
But now everything is fine and my rock64 boots from sd card like a charm. Yay!
Again: thank you for your quick and qualified help! This community is awesome!
...and now - I can start fiddling around with my sbc...