Hi,
I'm creating a Teensy 3.1 based device for scientific usage. For synchronizing clocks I'm doing a round trip from PC to Teensy and back to PC again and then process the results. I'm working under Linux (Mint 13, kernel 3.2.0-23).
The odd thing is that the round trip takes more time when the Teensy's USB cable is directly plugged in my PC compared to plugged in via an active 5m USB extender. When connected via the extender the round trip duration is about 80us..200us, whereas it is about 200us..1000us when plugged in directly.
Looking at the logs (attached) I noticed that in the slower/direct case the system uses uhci_hcd. In the faster/extender case the system uses ehci_hcd. Since communication works fine with the ehci_hcd driver I wonder why does the system decide it needs to use the uchi_hcd driver for the Teensy. Or better, can I do something on the Teensy side to tell the system that the plugged in device is a high speed device rather than a full speed device?
Theo
I'm creating a Teensy 3.1 based device for scientific usage. For synchronizing clocks I'm doing a round trip from PC to Teensy and back to PC again and then process the results. I'm working under Linux (Mint 13, kernel 3.2.0-23).
The odd thing is that the round trip takes more time when the Teensy's USB cable is directly plugged in my PC compared to plugged in via an active 5m USB extender. When connected via the extender the round trip duration is about 80us..200us, whereas it is about 200us..1000us when plugged in directly.
Looking at the logs (attached) I noticed that in the slower/direct case the system uses uhci_hcd. In the faster/extender case the system uses ehci_hcd. Since communication works fine with the ehci_hcd driver I wonder why does the system decide it needs to use the uchi_hcd driver for the Teensy. Or better, can I do something on the Teensy side to tell the system that the plugged in device is a high speed device rather than a full speed device?
Theo