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DWC OTG Error on Port Open #1652
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Why are you using |
@P33M We were experiencing data loss issues. We haven't been able to track down the root cause of the data loss, but adding |
Up to 80% of a frame is reserved for periodic traffic. At full-speed, the driver assumes that any periodic transfer can occur in any frame, thus bandwidth allocation to any endpoint is global. Full-speed is only 12mbit/s line rate therefore the max byte/s for periodic endpoints in totality is 1000/frame (1ms). The driver is additionally pessimistic in assuming line stuffing and device response times (which is the right thing to do). You're simply running out of bandwidth. This is a hard limit when running in full-speed mode. |
I have spotted that your hubs are single-TT hubs and your Arduinos expose 64-byte interrupt endpoints. See point 4 under Known Issues here: https://www.raspberrypi.org/documentation/hardware/raspberrypi/usb/README.md With multi-TT hubs it'll work a lot better at high speed. |
Raspberry Pi 3 Model B
Kernel version:
4.4.13-v7+
Subsystem: dwc_otg
Experiencing an issue opening serial ports to connected Atmel devices over USB. The Pi is configured using the
dwc_otg.speed=1
argument to make USB run atfull-speed
.We are running a Node.js app and using the
serialport
module to communicate with 8full-speed
devices connected using powered hubs. There are no other USB devices connected. When opening the ports, an error is thrown:NOTE: Each time the app is run, a different path is identified as the one causing the error (
ttyACM0
throughttyACM7
).This also causes
dmesg
output:Here is the
lsusb -v
outputThe text was updated successfully, but these errors were encountered: