Arduino > Movie player

Hi.
I have a little question in my head ... :cold_sweat:
I use the Arduino UNO board to control a Movie player.
The player has 4 inputs, 3 for 3bits encoding, and 1 for ground.

Arduino out Movie Player In
5 ---------------------- 1
6 ---------------------- 2
7 ---------------------- 4
GRD ------------------ GRD

The player wants a ground 'contact' to understand a 1 on its inputs
So I turn the ARduino Output HIGH when i want a 0, and LOW when i want a 1 in the player.
I can control the player, and all is good.
But i ask myself do i need to protect the output of the Arduino with Resistor ?
something like that ? Is it usefull or absolutly not ?

Arduino out Movie Player In
5 ----------R(10K)-------- 1
6 ----------R(10K)-------- 2
7 ----------R(10K)-------- 4
GRD ------------------ GRD

When i turn High an output, 5V goes through the cable ... and then what .... i don't know

Thank you for your help !!
:wink:

Current limiting resistors are always a good idea, especially if you don't know what the other side of the circuit looks like.

OK thank you for your advice.
I will

Unless of course they stop it working. When you output a high 5V can force current into the load, or source current. When you output low you suck current out of the load or sink current. Some circuits like TTL logic require a sink resistor no greater than 220R to work correctly.