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Good day, I hope you guys are good. My name is Francis From Nigeria.

I have been using raspberry for a while. I had to upgrade from Jessie to Stretch because my favorite raspberry pi 3B model is getting out of stock/supply.

I have an app that relies on USB modem, running lsusb gave the output below

Bus 001 Device 009: ID 05c6:6000 Qualcomm, Inc. Siemens SG75

running dmesg | grep "usb " gave the output below

[    0.705686] usb usb1: New USB device found, idVendor=1d6b, idProduct=0002, bcdDevice= 4.19
[    0.705698] usb usb1: New USB device strings: Mfr=3, Product=2, SerialNumber=1
[    0.705707] usb usb1: Product: DWC OTG Controller
[    0.705716] usb usb1: Manufacturer: Linux 4.19.66-v7+ dwc_otg_hcd
[    0.705725] usb usb1: SerialNumber: 3f980000.usb
[    1.141922] usb 1-1: new high-speed USB device number 2 using dwc_otg
[    1.382233] usb 1-1: New USB device found, idVendor=0424, idProduct=9514, bcdDevice= 2.00
[    1.382249] usb 1-1: New USB device strings: Mfr=0, Product=0, SerialNumber=0
[    1.701959] usb 1-1.1: new high-speed USB device number 3 using dwc_otg
[    1.832452] usb 1-1.1: New USB device found, idVendor=0424, idProduct=ec00, bcdDevice= 2.00
[    1.832485] usb 1-1.1: New USB device strings: Mfr=0, Product=0, SerialNumber=0
[  434.793043] usb 1-1.2: new high-speed USB device number 4 using dwc_otg
[  434.924784] usb 1-1.2: New USB device found, idVendor=05c6, idProduct=f000, bcdDevice= 0.00
[  434.924802] usb 1-1.2: New USB device strings: Mfr=3, Product=2, SerialNumber=4
[  434.924812] usb 1-1.2: Product: Qualcomm CDMA Technologies MSM
[  434.924822] usb 1-1.2: Manufacturer: Qualcomm, Incorporated
[  434.924831] usb 1-1.2: SerialNumber: 356793034849174
[  436.035767] usb 1-1.2: USB disconnect, device number 4
[  436.333111] usb 1-1.2: new high-speed USB device number 5 using dwc_otg
[  436.464923] usb 1-1.2: New USB device found, idVendor=05c6, idProduct=6000, bcdDevice= 0.00
[  436.464940] usb 1-1.2: New USB device strings: Mfr=3, Product=2, SerialNumber=4
[  436.464950] usb 1-1.2: Product: Qualcomm CDMA Technologies MSM
[  436.464960] usb 1-1.2: Manufacturer: Qualcomm, Incorporated
[  436.464969] usb 1-1.2: SerialNumber: 356793034849174
[  436.564312] usb 1-1.2: GSM modem (1-port) converter now attached to ttyUSB0
[  436.564991] usb 1-1.2: GSM modem (1-port) converter now attached to ttyUSB1
[  436.565620] usb 1-1.2: GSM modem (1-port) converter now attached to ttyUSB2
[  436.566413] usb 1-1.2: GSM modem (1-port) converter now attached to ttyUSB3
[  482.115780] usb 1-1.2: USB disconnect, device number 5
[  482.681598] usb 1-1.2: new high-speed USB device number 6 using dwc_otg
[  482.813286] usb 1-1.2: New USB device found, idVendor=05c6, idProduct=f000, bcdDevice= 0.00
[  482.813303] usb 1-1.2: New USB device strings: Mfr=3, Product=2, SerialNumber=4
[  482.813313] usb 1-1.2: Product: Qualcomm CDMA Technologies MSM
[  482.813323] usb 1-1.2: Manufacturer: Qualcomm, Incorporated
[  482.813333] usb 1-1.2: SerialNumber: 356793034849174
[  483.651760] usb 1-1.2: USB disconnect, device number 6
[  484.051553] usb 1-1.2: new high-speed USB device number 7 using dwc_otg
[  484.183407] usb 1-1.2: New USB device found, idVendor=05c6, idProduct=6000, bcdDevice= 0.00
[  484.183424] usb 1-1.2: New USB device strings: Mfr=3, Product=2, SerialNumber=4
[  484.183434] usb 1-1.2: Product: Qualcomm CDMA Technologies MSM
[  484.183444] usb 1-1.2: Manufacturer: Qualcomm, Incorporated
[  484.183453] usb 1-1.2: SerialNumber: 356793034849174
[  484.188709] usb 1-1.2: GSM modem (1-port) converter now attached to ttyUSB0
[  484.189920] usb 1-1.2: GSM modem (1-port) converter now attached to ttyUSB1
[  484.194207] usb 1-1.2: GSM modem (1-port) converter now attached to ttyUSB2
[  484.195467] usb 1-1.2: GSM modem (1-port) converter now attached to ttyUSB3
[  520.003856] usb 1-1.2: USB disconnect, device number 7
[  520.540541] usb 1-1.2: new high-speed USB device number 8 using dwc_otg
[  520.672438] usb 1-1.2: New USB device found, idVendor=05c6, idProduct=f000, bcdDevice= 0.00
[  520.672456] usb 1-1.2: New USB device strings: Mfr=3, Product=2, SerialNumber=4
[  520.672466] usb 1-1.2: Product: Qualcomm CDMA Technologies MSM
[  520.672476] usb 1-1.2: Manufacturer: Qualcomm, Incorporated
[  520.672485] usb 1-1.2: SerialNumber: 356793034849174
[  521.539737] usb 1-1.2: USB disconnect, device number 8
[  521.970415] usb 1-1.2: new high-speed USB device number 9 using dwc_otg
[  522.102347] usb 1-1.2: New USB device found, idVendor=05c6, idProduct=6000, bcdDevice= 0.00
[  522.102365] usb 1-1.2: New USB device strings: Mfr=3, Product=2, SerialNumber=4
[  522.102375] usb 1-1.2: Product: Qualcomm CDMA Technologies MSM
[  522.102384] usb 1-1.2: Manufacturer: Qualcomm, Incorporated
[  522.102406] usb 1-1.2: SerialNumber: 356793034849174
[  522.106482] usb 1-1.2: GSM modem (1-port) converter now attached to ttyUSB0
[  522.110038] usb 1-1.2: GSM modem (1-port) converter now attached to ttyUSB1
[  522.112073] usb 1-1.2: GSM modem (1-port) converter now attached to ttyUSB2
[  522.112993] usb 1-1.2: GSM modem (1-port) converter now attached to ttyUSB3

I usually use python 2.7 serial port module to interact with the modem in my previous jessie installation. I actually utilize 2 out of the available 4 ports for AT communication (i.e port '/dev/ttyUSB0' and '/dev/ttyUSB1'") and both works fine.

Supprisingly, i noticed that after i upgraded my operating system to stretch, only one of the port ('/dev/ttyUSB0') is functional for serial port communication, the other port no longer give any output following 'AT' command prompts.

I tried installing a clean version of buster image, but noticed the same thing, so i concluded that it has to do with the upgrade.

Pls can anyone suggest how i cant enable communication on both USB modem channels since both are very important for my application to function properly. Thanks in advance.

UPDATE: After upgrading to stretch, python raises the

"[Errno 32] Broken pipe"

when i tried assessing port /dev/ttyUSB1. This was not observed prior to the update. Also as I stated previously, I did a clean installation of Buster, and i noticed the same thing that only one (i.e. /dev/ttyUSB0 ) out of the 4 ports is functional as against 2 ports before the update.

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  • Expert Linux users CAN upgrade from an earlier release, but this is NOT recommended and becomes harder if not done soon after a new release. Do a fresh install of a new release. I suggest you install "Legacy" as IMO Bullseye is still too buggy. Forget python2 and then ask a question (describing what YOU did) if you need help.
    – Milliways
    Mar 14, 2022 at 22:53
  • UPDATE: After upgrading to stretch, python raises the "[Errno 32] Broken pipe" when i try assessing port /dev/ttyUSB1. This was not observed prior to the update.
    – ufumes
    Mar 14, 2022 at 22:57
  • Thanks for your suggestion @Milliways. I actually did a fresh installation with buster but still could only make use of one of the ports.
    – ufumes
    Mar 14, 2022 at 22:59
  • STOP posting Comments - EDIT your Question. Frankly, as written, I have no idea what you have or have done. I refuse to waste time on Stretch.
    – Milliways
    Mar 14, 2022 at 23:01

1 Answer 1

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I stumbled across a similar problem and answer on https://github.com/pyserial/pyserial/issues/59. I learnt that the problem is due to the serial function in python. I edited my serial port initialization code from port = serial.Serial(portid, baudrate=9600,timeout=0.1) to port = serial.Serial(portid, baudrate=9600,rtscts=True, dsrdtr=True, timeout=0.1) and i started getting feedbacks from both ports.

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