It did answer what I was looking for, its the number of open endpoints that matter, not the number of modems. I don't know what your usecase for the modems are, do you need to open all three ports per modem all the time ? Sorry for the delay My project requires at least 5 modems (2 serial ports per...

I have a question, does it behave differently if you open just one port on each modem. in stead of doing 0,1,2,3,4,5,6,7,8... do 0,3,6,9,1,4,7,10. ? Nope, it doesn't make any difference. The limitation is in the SoC USB peripheral, only 8 USB host channels are supported. i.e you can use max 7 USB s...

I decided to trace usb data with wireshark

when i open ttyUSB serial port there is plenty of "URB_BULK in" messages infinitely go to wireshark
here is pcap file

i added dwc_otg.speed=1 to /boot/cmdline.txt as suggested here https://www.raspberrypi.org/forums/viewtopic.php?f=28&t=53832 but problem still exists dmesg: [ 0.000000] Booting Linux on physical CPU 0xf00 [ 0.000000] Initializing cgroup subsys cpuset [ 0.000000] Initializing cgroup subsys cpu [ 0.00...

I experience problems with usb modems, please read this thread https://www.raspberrypi.org/forums/viewtopic.php?f=28&t=163184 (maybe you can help) First time i thought the problem is in internal usb hub LAN9514 so i decided to solder wires directly from broadcom SOC's OTG to my external usb hub. It ...

dmesg shows nothing when RPI hangs dmesg: [ 0.000000] Booting Linux on physical CPU 0xf00 [ 0.000000] Initializing cgroup subsys cpuset [ 0.000000] Initializing cgroup subsys cpu [ 0.000000] Initializing cgroup subsys cpuacct [ 0.000000] Linux version 4.4.22-v7+ (dc4@dc4-XPS13-9333) (gcc version 4.9...

lsusb: Bus 001 Device 004: ID 413c:2107 Dell Computer Corp. Bus 001 Device 008: ID 12d1:1001 Huawei Technologies Co., Ltd. E169/E620/E800 HSDPA Modem Bus 001 Device 010: ID 12d1:1001 Huawei Technologies Co., Ltd. E169/E620/E800 HSDPA Modem Bus 001 Device 007: ID 1a40:0101 Terminus Technology Inc. 4-...

RPI hangs when i consequently open ttyUSB ports on 3 gsm modems It is stay freeze until i remove usb modems each modem has 3 ttyUSB serial ports for example huawei e153 /dev/ttyUSB0 - modem port /dev/ttyUSB1 - data port /dev/ttyUSB2 - audio port This gsm modem uses "option" kernel module i wrote sim...