Spurious "noise" on servos with UART

Hello,

I am having a strange problem :o.

I have an Arduino Uno and a Raspberry Pi connected through each other's UART pins. They communicate perfectly fine with each other and I'm able to send commands to the Arduino from the RPi.

Two DGServo S04NF servos are connected to the Arduino PWM pins 9 and 10.

Everything is powered by a 6xAA battery pack (directly to Arduino and regulator) and a 5V voltage regulator board (directly to Pi and servos). The Pi and the Arduino grounds are also connected.

The problem is that every time there's UART activity between the Pi and the Arduino (either direction) I get what I think it's spurious noise on the servos pins that make them move forward a bit.

Does any of you have a hint on what might be happening here?

Thank you for reading this, cheers,

AP

I have an Arduino Uno and a Raspberry Pi connected through each other’s UART pins. They communicate perfectly fine with each other and I’m able to send commands to the Arduino from the RPi.

Since the Arduino Uno is 5V and the Raspberry Pi is 3.3V (not 5V tolerant) I can’t see how you haven’t fried your
Raspberry Pi? Check or confirm you’ve addressed this issue before proceeding, its an expensive
mistake to make.