In built loopback test

[CarlFK]

The board should be able to test itself if an input is hooked to an output.
hdmi cable from output0 to input0

H2U 00:26:36>o0 on
Enabling output0
H2U 00:26:42>i0 on
Enabling input0
H2U 00:26:44>x c p 0
Connecting pattern to output0
H2U 00:26:55>test loopback o0 01
test passed.

It can test edid and picture data and maybe more.

[mithro]

This should be pretty easy to do in the softcpu firmware already.

The steps would be;

1. Add a method for calculating a checksum / CRC across a region of memory.
2. Add a method for writing the next input frame to a different region of memory.
3. Calculate checksum / CRC over both regions and compare.

I believe that @cr1901 has already added some checksum / CRC code to the firmware so step (1) might already be done.