The Olive O4HD Serial Port

While troubleshooting boot anomalies with my Olive O4HD I thought it would be incredibly helpful to have raw console output from the boot process. To achieve this I examined the populated and unpopulated pin headers on the motherboard with a logic analyzer.

Easily enough I found CON1, conveniently populated from the manufacturer with a six-pin header, outputting serial data at 115200bps. The pins are numbered left to right on this header: pin 4 is ground, pin 5 is receive, and pin 6 is transmit. During boot it’s possible to observe and interact with the uboot bootstrap environment and the Linux boot process over this port. After boot the port has an unsecured shell running as root which can be used.

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