Problems with EEB configuration after adding Servo (1 reply)

When I added a servo to my EEB configuration, the servo goes crazy when the layer fans come on.

Modded A8 with RAMPS 1.4 and Marlin, with the following fan/servo pins configured:
FAN_PIN 5
E0_AUTO_FAN_PIN 4
E1_AUTO_FAN_PIN 4
SERVO0_PIN 11

I made a dual extruder setup, changed Marlin to EEB and used a fan extender board in the servo header to run the hotend and layer fans. I added a servo for the Z-probe (had to shift the extender board by 2 pins so it uses D4,D5 but that worked fine) and the servo deploys and retracts perfectly.

Problem comes when I hit layer 4 and the fan comes on... the servo goes mental and after a few seconds the computer loses comms with the printer. It then appears on another ttyACMx port.

I tried the following without success:
1. Moving the servo from D11 to D6 and changing the pin assignment in pins_RAMPS.h
2. Removing the Vcc/5v jumper and powering the servo connector directly from 5v (vie the remaining GND/5v pins in the servo header block)
3. Replacing the USB cable

Now I'm wondering whether Marling uses a different PWM mode for servos and for fans, and if so whether there's a workaround.

Also somewhat confused as to why the USB port would be affect, and why it then directly reappears as a new com port.

Any suggestions greatly appreciated.

Thanks,
Phil