New electrodragon board version with E line problem?

[jonms]

I ordered some electrodragon boards and they are marked as V 2-2. They look different to the pictures elsewhere and appear to have a problem with the E line.

My existing setup works fine with the adafruit bonnet, so I know the matrix boards are good.

With the electrodragon boards I get the ‘missing band’ you’d expect without the E line.

After trying every conceivable option combination with the test/demos I put a logic analyser on the output and found there’s no E line signal on pin 4 or 8, regardless of jumper configurations.

Checking the board the traces from the ‘E_buf’ pads go directly to pin 4 - this confirmed visually and with a circuit tester.

Checking with a scope, there’s no signal on any of the jumper pads - they’re floating/ground.

Has anyone encountered this?

I can’t help feeling I’ve missed something… however the logic/scope/tester make me think something’s astray… and all of the 3 boards I received are the same.

Any thoughts, help, insight or comment welcome!

(The pic of the back of the board clearly shows the line from the E_buf jumper pad to pin 4)

[jonms]

Further investigation.

Removing the matrix so the board doesn’t have any load gives the result below - the names refer to the E-select jumper pad in the top right of the board (top view).

Under load all lines go to GND except for the p4 pads which go to +5V.

Multiple problems here - behaviour under load, signal where it shouldn’t be and a strobe rather than E -line.

Like I said - I may have missed something here… happy to be corrected, educated and pointed in the right direction

No Load

Under Load

[hechaogm]

There is a indeed a board issue.

Please see the explanation here: MPC1119-error-dat.md

[jonms]

Many thanks @hechaogm - greatly appreciated!

The fix works… although I had to cut the traces in the two positions marked by red crosses in the diagram (the trace between the two E_BUF pads remains intact).

Can you confirm this is expected/correct?