I am using the suggestion of a TRS Y-cable (insert cable) to try connecting pedals 1&2 to the H9000R PEDAL1 input and pedals 3&4 to the H9000R PEDAL2 input.
I then go into the Setup screen to calibrate the pedals, making sure to select the PEDAL1 mode to 2 expression pedals.
Then As i try to calibrate the Tip and Ring, what happens, with both of the expression pedals, is that with the calibration bar correctly starts at zero with the pedal in full up position (fully depressed) then around the mid point of the pedal being pressed, the bar peaks at 100%, then it goes back down to zero as the pedal is fully engaged. Obviously, I checked that the same problem doesn’t happen with a regular TRS midi cable and the H9000R setup as One expression pedal.
Out of desperation, I tried inserting the mono (TS) cable into each of the two pedals but inserted to the “first click” only, not fully inserted.
It now works with the caveat that the pedals only go up to 75% and not 100%, but I assume the calibration in fact adjusts for that.
This is a studio setup so the fact that the cables are not fully inserted is probably ok but I wonder if it means that I need a special wiring on the Y-cable, as I used a straight insert cable. It seems like the common ground shared by the two pedals creates a problem for these pedals, which are Boss FV500-L.
So any suggestion about rewiring of the cables would be welcome so I can fully insert them.