Tinkerkit DMX shield can't use digital pin 4 for IO

Hi, I wan’t to know how to know the available pins after using the shield for dmx send only.
I don’t need to receive dmx, and I need several free pins.

i don’t see on the library (DmxMaster/DmxMaster.cpp at master · TinkerKit/DmxMaster · GitHub) if there is any way to change the default pins; pin 4 is not named.

I don’t know if its something related to timers or just because de pcb paths.

I can see the schematics here (https://www.openhacks.com/uploadsproductos/dmx_shield_rev4.pdf) but I don’t understand too much…

Ps: I have the analog pins unused, so I can setuo them as digital IO, but is not ideal because I need to resold some cable connector that I have done…

Any help is appreciated

The DMX shiled diagram you linked...

J1 and J3 (top/left) are connected to Uno pins 0-13, but they are numbered differently.

Start from the right (J1) with 0(RX), 1(TX), etc.
You see that pin 0-6 is used. 7-13 is free (the next pin is ground).

A2 is also used (analogue connector, left side).

Power connector should be obvious.