Teensy 4.1 decrease USB speed from 480 Mhz


Active member

Is that possible to decrease the USB speed of the CHIP of teensy 4.1 from 480 MHz (the main, not the host)?
We have some issue with the wiring/cabling, and we can not change the wiring, and probebly it is do to the high speed.

Yes, it is possible, but to do so you'll need to edit the USB code in the core library.

Look for this line in usb.c:

    //USB1_PORTSC1 |= USB_PORTSC1_PFSC; // force 12 Mbit/sec

Just uncomment and save. Arduino IDE should automatically notice you've edited the file and rebuild it on the next upload. When Teensy starts up it will use 12 MBit/sec speed.
Hi Paul, Works great for the chip Serial. However when we program/flash the chip we get the same problem. Is that possible to change the speed of the flashing as well?
Sadly no, there isn't a way to configure USB speed for loading code. I might add this at some point in the future, but it's definitely not supported now (bootloader version 1.07 or 1.08).