Hi, we’ve designed a custom board to work with the Jetson Xavier NX. However, when we connect it via HDMI, we’re encountering an “EDID invalid” error. Attached is the schematic for the HDMI connection.
I can’t answer about the schematic, but will add some related comments.
EDID uses the i2c protocol over the DDC wire. The device tree will change if the power rails to the wire which powers that i2c of the monitor (that power is provided by the HDMI) fail or provide power. There is also a hot plug detect, related to GPIO, which won’t work correctly if the device tree does not set this up correctly.
One easy test, since HDMI is hot plug, is to monitor “dmesg --follow”, and then to plug in the HDMI cable to see what logs appear. This can tell you if the HDMI detection worked. If you measure for the i2c rail, then this should be powered on detect. If all of that is good, then you will want to monitor the i2c with a protocol analyzer. If the EDID is correctly transferring, then it might be related to the driver instead of the hardware.
Note that the driver for the GPU allows only EDID configuration.
A large part of the time it is a case of the device tree not being correct. Sometimes it could be a quality issue when a trace is the wrong length or impedance.
You should follow Design Guide and reference schematic (P3509) in DLC for CEC design as showing below.
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