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The USB-HUB is self-powered, and two LTE modules are connected via USB-SERIAL to USB-HUB. We are facing a problem is that,The devices which are connected to USB-HUB can not be accessed. Is there any investigation method and solution for this?

Below following are kernel Logs.

Kerenl log:

19:47:58 raspberrypi kernel: [ 9301.001438] usb usb1-port1: disabled by hub (EMI?), re-enabling...

19:47:58 raspberrypi kernel: [ 9301.001457] usb 1-1: USB disconnect, device number 11

19:47:58 raspberrypi kernel: [ 9301.001463] usb 1-1.1: USB disconnect, device number 12

19:47:58 raspberrypi kernel: [ 9301.001668] ftdi_sio ttyUSB2: error from flowcontrol urb

19:47:58 raspberrypi kernel: [ 9301.001872] ftdi_sio ttyUSB2: FTDI USB Serial Device converter now disconnected from ttyUSB2

19:47:58 raspberrypi kernel: [ 9301.001906] ftdi_sio 1-1.1:1.0: device disconnected

19:47:58 raspberrypi kernel: [ 9301.002107] ftdi_sio ttyUSB3: error from flowcontrol urb

19:47:58 raspberrypi kernel: [ 9301.003371] ftdi_sio ttyUSB3: FTDI USB Serial Device converter now disconnected from ttyUSB3

19:47:58 raspberrypi kernel: [ 9301.003429] ftdi_sio 1-1.1:1.1: device disconnected

19:47:58 raspberrypi kernel: [ 9301.010150] ftdi_sio ttyUSB4: FTDI USB Serial Device converter now disconnected from ttyUSB4

19:47:58 raspberrypi kernel: [ 9301.010212] ftdi_sio 1-1.1:1.2: device disconnected

19:47:58 raspberrypi kernel: [ 9301.010430] ftdi_sio ttyUSB5: error from flowcontrol urb

19:47:58 raspberrypi kernel: [ 9301.018012] ftdi_sio ttyUSB5: FTDI USB Serial Device converter now disconnected from ttyUSB5

I will appreciate your help and time

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Question

Setup = Rpi > USB HUB > USB TTL adapter/cable > 2 LTE modules.

Protocol = AT Commands.

Problem = LTE module not detected.

Question = Any investigation method and solution?

Answer

  1. First test one module, not two.

  2. First test Rpi UART, not USB/UART.

  3. First test Rpi hardware/software using a simple loop back program.

  4. If Rpi UART ok, then test USB UART loopback.

  5. First test USB UART without HUB, then with HUB.

  6. First test simple request AT, response OK, then test rest.

Update 2019may24hkt1342

Now about the hub problem.

  1. Not all hubs are compatible with Rpi.

  2. Even if the hub is OK, not all USB UART/serial adapters/cable works with it well. I found most adapters with CH340 and PL2000 driver good with Rpi3B+ stretch 9.

  3. If in doubt, try connect the serial device direct to Rpi's standard USB sockets. For Rpi Zero without stand USB sockets, then try your luck with another USB hub.

You can also using linux terminal command "lsusb" to make sure if USB hub is detected.

usb hub detection

References

Testing Rpi UART serial loopback

Testing USB UART serial loopback

How to setup USB UART serial ports

AliExpress 4G LTE Module with serial port

GPRS/GSM/Heyes AT Commands Reference - Telit

GPS AT Command Reference - Option Wireless

Raspberry Pi GSM Module – Mobile Internet (LTE, 3G, UMTS)

The Raspberry Pi can be connected to the Internet very quickly and easily via the local network. But what if you also need a mobile Internet connection outside your own WLAN? There are GSM modules / Surfsticks (mostly from Huawei), which can be connected via USB. Sometimes are such GSM modules, which support 3G, UMTS and sometimes even LTE, given free with a mobile phone contract which includes an Internet option.

This tutorial shows how to connect Raspberry Pi to the internet using GSM modules.

If there is not something like Bus 001 Device 008: ID xyz ... standing, the GSM module on the Raspberry Pi has not yet been recognized.

So we need to install appropriate drivers.

  • Thank you so much for your reply . Today we tried with single port but we faced the same problem like below. 19:47:58 raspberrypi kernel: [ 9301.001438] usb usb1-port1: disabled by hub (EMI?), re-enabling... So the error "Disabled by hub (EMI?)" is the impact of Noise or Static electricity? Can you please tell me. I am awaiting for your answer. – Praveen Deshmane May 24 at 5:38
  • Well very little chance of noise or static electricity problem. More likely the hub itself has a problem. Do you have any USB serial adapter/cable to test, instead of the LTE module? Also see my answer updated just now. – tlfong01 May 24 at 5:52
  • You can also use terminal command "lsusb" to make sure if USB hub is detected. One more thing, you can debug LTE module without using Rpi python program, but use terminal emulator RealTerm under Windows 7/10 to talk to lte device. In other words, isolate Rpi and use Windows RealTerm to check if LTE module can talk AT commands. Of course you can also use Rpi puTTY instead of Windows puTTY/TeraTerm/RealTerm. – tlfong01 May 24 at 7:57
  • Not sure which LTE module you are using. Is it similar to the following: Raspberry Pi GSM Module – Mobile Internet (LTE, 3G, UMTS) tutorials-raspberrypi.com/… – tlfong01 May 27 at 1:51
  • 1) We are evaluating using CM3. 2) USB hub and USB-UART are boarded on the IO board. 3) USB hub is working in Self-power mode. 4) VBUS-detect of USB-hub uses the same 3.3V power supply as CM3. 5) Set correctly when in Power-On. – Praveen Deshmane May 27 at 5:28

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