# Unable to open port while calibrating ESC

Source: https://forum.modalai.com/topic/832/unable-to-open-port-while-calibrating-esc
Category: Flight Core and Legacy VOXL (https://forum.modalai.com/category/9/flight-core-and-legacy-voxl)
Tags: flight-core
Posted: 2022-03-31 22:52:25 UTC by Jimk_Aero
Replies: 1 · Views: 1416

## Jimk_Aero · 2022-03-31 22:52:25 UTC

At the point in the ESC calibration python program where I attach the USB cable and reconnect power to our flight core, I receive the following message:
Using portname /dev/serial/by-id/usb-ModalAI_PX4_FMU_ModalAI_FCv1_0-if00
connecting...
Error: Unable to open port

I'm using Castle Multi-Roto 35 ESC's and I cannot get all the motors to spin.

This is my last try.  I've about given up on the flight core.

## Reply by modaltb (ModalAI staff) · 2022-04-01 15:27:24 UTC

Hi @Jimk_Aero ,

Sorry to hear about the problems.  Not being able to power off USB does make this hard and is a carry over from the VOXL Flight....

- Even without ESC calibration, you can manually attempt to spin a motor, if using PWM, via this: https://dev.px4.io/master/en/middleware/modules_command.html#pwm
Do you have an oscilliscope?  You could probe the PWM channel output pretty easy (pins 2-5 for a quad) and see if you see any signal coming out of the board.  If there's no signal, when you expect it, on a single channel, try to look at those ESD diodes right next to the connector and check for any fried parts.

- PX4 FW version you are running?  There are two programs to handle some edge cases, `px4-esc-cal-tool-v1-11.py` and `px4-esc-cal-tool.py`