# MC7455 USB device disconnects immediately **URL:** \ **Category:** MC/EM Series\ **Created:** [August 14, 2017, 2:23pm UTC](https://forum.sierrawireless.com/t/mc7455-usb-device-disconnects-immediately/9415 "2017-08-14T14:23:04Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![evk1206](https://sea1.discourse-cdn.com/flex025/user_avatar/forum.sierrawireless.com/evk1206/32/3772_2.png) [@evk1206](https://forum.sierrawireless.com/u/evk1206)\ **Post date:** [August 14, 2017, 2:23pm UTC](https://forum.sierrawireless.com/t/mc7455-usb-device-disconnects-immediately/9415/1 "2017-08-14T14:23:04Z")
Hello, ``` I am working on an IOT product, where we are planning to use Sierra MC7455 chip as an LTE Modem and also for GNSS. We are using Yocto based build system, so I could configure the Linux Kernel and build again. ``` The kernel version used is 4.9.39. I have enabled the Sierra Wireless config for USB\_Serial in kernel config. After turning on the system I could see that the chip keeps on connecting and disconnecting immediately. The logs are as follows: qcserial 1-1.3:1.0: device disconnected usb 1-1.3: new high-speed USB device number 23 using ci\_hdrc usb 1-1.3: New USB device found, idVendor=1199, idProduct=9070 usb 1-1.3: New USB device strings: Mfr=1, Product=2, SerialNumber=3 usb 1-1.3: Product: Sierra Wireless MC7455 Qualcomm usb 1-1.3: Manufacturer: Sierra Wireless, Incorporated usb 1-1.3: SerialNumber: LQ71660082041020 qcserial 1-1.3:1.0: Qualcomm USB modem converter detected usb 1-1.3: Qualcomm USB modem converter now attached to ttyUSB0 usb 1-1.3: USB disconnect, device number 23 qcserial ttyUSB0: Qualcomm USB modem converter now disconnected from ttyUSB0 qcserial 1-1.3:1.0: device disconnected usb 1-1.3: new high-speed USB device number 24 using ci\_hdrc usb 1-1.3: New USB device found, idVendor=1199, idProduct=9070 usb 1-1.3: New USB device strings: Mfr=1, Product=2, SerialNumber=3 usb 1-1.3: Product: Sierra Wireless MC7455 Qualcomm usb 1-1.3: Manufacturer: Sierra Wireless, Incorporated usb 1-1.3: SerialNumber: LQ71660082041020 qcserial 1-1.3:1.0: Qualcomm USB modem converter detected usb 1-1.3: Qualcomm USB modem converter now attached to ttyUSB0 usb 1-1.3: USB disconnect, device number 24 qcserial ttyUSB0: Qualcomm USB modem converter now disconnected from ttyUSB0 qcserial 1-1.3:1.0: device disconnected Please let me know, how to solve this issue. I have libqmi installed from the Yocto build. I have also flashed the latest firmware from Sierra - 9999999\_9904609\_SWI9X30C\_02.24.03.00\_00\_GENERIC\_002.021\_000.exe Thanks & Regards, Vinothkumar ---
**Author:** ![mlw](https://sea1.discourse-cdn.com/flex025/user_avatar/forum.sierrawireless.com/mlw/32/3706_2.png) [@mlw](https://forum.sierrawireless.com/u/mlw)\ **Post date:** [August 15, 2017, 8:31am UTC](https://forum.sierrawireless.com/t/mc7455-usb-device-disconnects-immediately/9415/2 "2017-08-15T08:31:50Z")
Vino, I cannot really tell you why this would be doing it but I would STRONGLY recommend that you use our GobiSerial and GobiNet drivers, the open source ones are used widely as is qmilib but they can have unpredictable behaviour which is why we have our own (and our own equivalent of qmilib). Regards Matt ---
**Author:** ![dl5162](https://sea1.discourse-cdn.com/flex025/user_avatar/forum.sierrawireless.com/dl5162/32/2169_2.png) [@dl5162](https://forum.sierrawireless.com/u/dl5162)\ **Post date:** [August 15, 2017, 12:21pm UTC](https://forum.sierrawireless.com/t/mc7455-usb-device-disconnects-immediately/9415/3 "2017-08-15T12:21:48Z")
The modem is looping in bootloader mode without ever enumerating in application mode. It’s unlikely that drivers, or any other part of the host sotware or hardware, makes any difference. The bootloader should eventually enter failsafe mode where the ramdump tool from the SDK can be used to help analyzing the crash. I recommend using SWI support for this. ---
**Author:** ![evk1206](https://sea1.discourse-cdn.com/flex025/user_avatar/forum.sierrawireless.com/evk1206/32/3772_2.png) [@evk1206](https://forum.sierrawireless.com/u/evk1206)\ **Post date:** [August 16, 2017, 9:42am UTC](https://forum.sierrawireless.com/t/mc7455-usb-device-disconnects-immediately/9415/4 "2017-08-16T09:42:23Z")
> [@mlw](#): > > Vino, > > I cannot really tell you why this would be doing it but I would STRONGLY recommend that you use our GobiSerial and GobiNet drivers, the open source ones are used widely as is qmilib but they can have unpredictable behaviour which is why we have our own (and our own equivalent of qmilib). > > Regards > > Matt Hi, I have an update. I tried to use USB to mini-PCIe convertor. Surprisingly, if I connect to my hardware using USB to mini-PCIe, the chip is getting identified and is working fine. But if I tried to connect to the PCIe slot its not working, the device gets disconnected immediately and is trying to connect again. Not sure whats happening , do you have any suggestion. Regards, Vinothkumar ---
**Author:** ![mlw](https://sea1.discourse-cdn.com/flex025/user_avatar/forum.sierrawireless.com/mlw/32/3706_2.png) [@mlw](https://forum.sierrawireless.com/u/mlw)\ **Post date:** [August 16, 2017, 9:48am UTC](https://forum.sierrawireless.com/t/mc7455-usb-device-disconnects-immediately/9415/5 "2017-08-16T09:48:50Z")
Vino, Are you plugging this into a PCIe slot on a laptop? If so then the PC OEM’slock these down pretty hard as it is for their use only, it will probably be a secret setting somewhere in the BIOS. Can’t help you there. Regards Matt ---
**Author:** ![evk1206](https://sea1.discourse-cdn.com/flex025/user_avatar/forum.sierrawireless.com/evk1206/32/3772_2.png) [@evk1206](https://forum.sierrawireless.com/u/evk1206)\ **Post date:** [August 16, 2017, 1:03pm UTC](https://forum.sierrawireless.com/t/mc7455-usb-device-disconnects-immediately/9415/6 "2017-08-16T13:03:10Z")
Hi, No. I am using an embedded hardware from Compulab. [compulab.com/products/comput … /#overview](http://www.compulab.com/products/computer-on-modules/cl-som-imx7-freescale-i-mx-7-system-on-module/#overview) I have used the pcie slot with TELIT chips, it worked fine. Regards, Vinothkumar ---
**Author:** ![dl5162](https://sea1.discourse-cdn.com/flex025/user_avatar/forum.sierrawireless.com/dl5162/32/2169_2.png) [@dl5162](https://forum.sierrawireless.com/u/dl5162)\ **Post date:** [August 16, 2017, 1:21pm UTC](https://forum.sierrawireless.com/t/mc7455-usb-device-disconnects-immediately/9415/7 "2017-08-16T13:21:48Z")
I assume the slot on the board is configured for PCIe and not USB3 SS? Did you cover the USB3 TX/RX pins on the modem? If not, then try that. ---
**Author:** ![evk1206](https://sea1.discourse-cdn.com/flex025/user_avatar/forum.sierrawireless.com/evk1206/32/3772_2.png) [@evk1206](https://forum.sierrawireless.com/u/evk1206)\ **Post date:** [September 15, 2017, 7:08am UTC](https://forum.sierrawireless.com/t/mc7455-usb-device-disconnects-immediately/9415/8 "2017-09-15T07:08:30Z")
Hi, I tried masking the USB pins (USb3 Tx and RX pins) . I have attached the image. Still I am facing the same issue when I connect the module over PCiE. The device enters into boot mode and loops repeatedly. qcserial ttyUSB0: Qualcomm USB modem converter now disconnected from ttyUSB0 qcserial 1-1.3:1.0: device disconnected usb 1-1.3: new high-speed USB device number 26 using ci\_hdrc usb 1-1.3: New USB device found, idVendor=1199, idProduct=9070 usb 1-1.3: New USB device strings: Mfr=1, Product=2, SerialNumber=3 usb 1-1.3: Product: Sierra Wireless MC7455 Qualcomm usb 1-1.3: Manufacturer: Sierra Wireless, Incorporated usb 1-1.3: SerialNumber: LQ71660022021020 qcserial 1-1.3:1.0: Qualcomm USB modem converter detected usb 1-1.3: Qualcomm USB modem converter now attached to ttyUSB0 usb 1-1.3: USB disconnect, device number 26 qcserial ttyUSB0: Qualcomm USB modem converter now disconnected from ttyUSB0 qcserial 1-1.3:1.0: device disconnected Any info on the topic would be helpful. Regards, Vinothkumar ![](https://us1.discourse-cdn.com/flex025/uploads/sierrawireless/original/2X/f/f4794fb70765ef547ee013f83be80d35c8059a88.jpg) ---
**Author:** ![mlw](https://sea1.discourse-cdn.com/flex025/user_avatar/forum.sierrawireless.com/mlw/32/3706_2.png) [@mlw](https://forum.sierrawireless.com/u/mlw)\ **Post date:** [September 15, 2017, 1:44pm UTC](https://forum.sierrawireless.com/t/mc7455-usb-device-disconnects-immediately/9415/9 "2017-09-15T13:44:34Z")
Vino, I think you need to check the full pin out of the PC board you are using and compare it to the MC74 one. there may be some other incompatibility. Regards Matt ---
**Author:** ![evk1206](https://sea1.discourse-cdn.com/flex025/user_avatar/forum.sierrawireless.com/evk1206/32/3772_2.png) [@evk1206](https://forum.sierrawireless.com/u/evk1206)\ **Post date:** [September 18, 2017, 7:25am UTC](https://forum.sierrawireless.com/t/mc7455-usb-device-disconnects-immediately/9415/10 "2017-09-18T07:25:47Z")
Hi, After lot of tries with masking the pins, I could succesfully connect the MC7455 to my system using PCIe. I have masked the following pins: USB3 masking -\> Pin 23,25,27,29,31,33 and also the following pins: Pin 20 - W\_DIABLE\_N Pin 22 - SYSTEM\_RESET\_N Pin 24 - Vcc I am not sure why masking these pins are necessary. Any information on side effects of masking these pins would be helpful. Regards, Vinothkumar Regards, Vinoth ---
**Author:** ![mlw](https://sea1.discourse-cdn.com/flex025/user_avatar/forum.sierrawireless.com/mlw/32/3706_2.png) [@mlw](https://forum.sierrawireless.com/u/mlw)\ **Post date:** [September 18, 2017, 7:38am UTC](https://forum.sierrawireless.com/t/mc7455-usb-device-disconnects-immediately/9415/11 "2017-09-18T07:38:26Z")
Vino, If the pins are in the wrong level or the unit is detecting activity on then not consistent with USB 3.0 then it causes issues with enumeration of the unit to the host. Regards Matt ---
**Author:** ![AJ23](https://avatars.discourse-cdn.com/v4/letter/a/8491ac/32.png) [@AJ23](https://forum.sierrawireless.com/u/AJ23)\ **Post date:** [February 22, 2024, 12:02pm UTC](https://forum.sierrawireless.com/t/mc7455-usb-device-disconnects-immediately/9415/12 "2024-02-22T12:02:54Z")
I am also facing this issue using the Ubuntu 22.04 Desktop version & Kernal version 6.5.0-18-generic USB 1-1.3 Qualcomm USB modem converter MC7304 & MC7430, Pls help to resolve this issue. ---
**Author:** ![jyijyi](https://sea1.discourse-cdn.com/flex025/user_avatar/forum.sierrawireless.com/jyijyi/32/4766_2.png) [@jyijyi](https://forum.sierrawireless.com/u/jyijyi)\ **Post date:** [February 22, 2024, 1:22pm UTC](https://forum.sierrawireless.com/t/mc7455-usb-device-disconnects-immediately/9415/13 "2024-02-22T13:22:11Z")
What usb driver have you installed? Can you post the kernel log when connected with the module? ---
**Author:** ![AJ23](https://avatars.discourse-cdn.com/v4/letter/a/8491ac/32.png) [@AJ23](https://forum.sierrawireless.com/u/AJ23)\ **Post date:** [February 22, 2024, 2:19pm UTC](https://forum.sierrawireless.com/t/mc7455-usb-device-disconnects-immediately/9415/14 "2024-02-22T14:19:51Z")
> [@jyijyi](#): > > kernel log Hi Thanks for the reply pls following details Feb 22 19:47:31 lamhas-pro kernel: [5288.774495] qcserial 1-1.3:1 .0: Qualcomm USB modem converter detected Feb 22 19:47:31 lamhas-pro kernel: [5288.774600] usb 1-1.3: Qualc omm USB modem converter now attached to ttyUSB3 Feb 22 19:47:31 lamhas-pro kernel: [5288.774997] qcserial 1-1.3:1 .2: Qualcomm USB modem converter detected Feb 22 19:47:31 lamhas-pro kernel: [5288.775056] usb 1-1.3: Qualc omm USB modem converter now attached to ttyUSB4 Feb 22 19:47:31 lamhas-pro kernel: [5288.775364] qcserial 1-1.3:1 .3: Qualcomm USB modem converter detected Feb 22 19:47:31 lamhas-pro kernel: [5288.775428] usb 1-1.3: Qualc omm USB modem converter now attached to ttyUSB5 Feb 22 19:47:31 lamhas-pro kernel: [5288.775777] qmi\_wwan 1-1.3:1 .8: cdc-wdm3: USB WDM device Feb 22 19:47:31 lamhas-pro kernel: [5288.776136] qmi\_wwan 1-1.3:1 .8 wwan2: register ‘qmi\_wwan’ at usb-0000:00:1a.0-1.3, WWAN/QMI de vice, 9a:57:24:3d:ca:c1 Feb 22 19:47:31 lamhas-pro kernel: [5288.776557] qmi\_wwan 1-1.3:1 .10: cdc-wdm4: USB WDM device Feb 22 19:47:31 lamhas-pro kernel: [5288.776832] qmi\_wwan 1-1.3:1 .10 wwan3: register ‘qmi\_wwan’ at usb-0000:00:1a.0-1.3, WWAN/QMI d evice, 9a:57:24:3d:ca:c1 ![modem](https://us1.discourse-cdn.com/flex025/uploads/sierrawireless/original/2X/e/e5c80f83c67a99dbeda34d2254e0b534da6ae9a9.png) ---
**Author:** ![jyijyi](https://sea1.discourse-cdn.com/flex025/user_avatar/forum.sierrawireless.com/jyijyi/32/4766_2.png) [@jyijyi](https://forum.sierrawireless.com/u/jyijyi)\ **Post date:** [February 22, 2024, 2:42pm UTC](https://forum.sierrawireless.com/t/mc7455-usb-device-disconnects-immediately/9415/15 "2024-02-22T14:42:34Z")
are you installing the MBPL USB driver? [https://source.sierrawireless.com/resources/airprime/software/mbpl/mbpl-software-latest/#sthash.ZXRwiiKx.pnQ5zaB5.dpbs](https://source.sierrawireless.com/resources/airprime/software/mbpl/mbpl-software-latest/#sthash.ZXRwiiKx.pnQ5zaB5.dpbs) What is the current issue you are facing now? Have you tried to establish data connection with the MBPL SDK? > [@Example on establishing data connection by AT!SCACT via MBPL R20 driver](https://forum.sierrawireless.com/t/example-on-establishing-data-connection-by-at-scact-via-mbpl-r20-driver/24130): > > Here is an example to establish data connection by AT!SCACT via MBPL R20 driver: Module: WP7609 FW: R13 MBPL: R20 PC Environment: Ubuntu 18 need to install the MBPL R20 driver for qmi\_wwan and qcserial (MBPL\_Drivers\_USB\_R20\_ENG1-src.tar.gz) avoid the Ubuntu changing the network name: ln -s /dev/null /etc/systemd/network/99-default.link sudo apt-get install libqmi-utils sudo apt-get install udhcpc now insert the USB to PC sudo chmod 777 /sys/class/net/wwan0/qmi/raw\_ip … ---
**Author:** ![AJ23](https://avatars.discourse-cdn.com/v4/letter/a/8491ac/32.png) [@AJ23](https://forum.sierrawireless.com/u/AJ23)\ **Post date:** [February 22, 2024, 3:36pm UTC](https://forum.sierrawireless.com/t/mc7455-usb-device-disconnects-immediately/9415/16 "2024-02-22T15:36:36Z")
“I am currently using Ubuntu 22.04 and I am facing an issue where my modems keep disconnecting and reconnecting frequently. I have not installed any drivers. Can you please let me know if I need to install one? If yes, what is the procedure to do so?” ---
**Author:** ![jyijyi](https://sea1.discourse-cdn.com/flex025/user_avatar/forum.sierrawireless.com/jyijyi/32/4766_2.png) [@jyijyi](https://forum.sierrawireless.com/u/jyijyi)\ **Post date:** [February 22, 2024, 3:45pm UTC](https://forum.sierrawireless.com/t/mc7455-usb-device-disconnects-immediately/9415/17 "2024-02-22T15:45:17Z")
you can see this document as example: > [@Example on establishing data connection by AT!SCACT via MBPL R20 driver](https://forum.sierrawireless.com/t/example-on-establishing-data-connection-by-at-scact-via-mbpl-r20-driver/24130/2): > > I have also made a document to summarize how to establish data connection by connection manager in MBPL R20 SDK. [Example on establishing data connection by MBPL R20.docx](https://forum.sierrawireless.com/uploads/short-url/bU2LlOOimQIbqM9do7VxbWynZaf.docx) (165.1 KB) ---
**Author:** ![AJ23](https://avatars.discourse-cdn.com/v4/letter/a/8491ac/32.png) [@AJ23](https://forum.sierrawireless.com/u/AJ23)\ **Post date:** [February 22, 2024, 4:16pm UTC](https://forum.sierrawireless.com/t/mc7455-usb-device-disconnects-immediately/9415/18 "2024-02-22T16:16:10Z")
The download page showing the latest release pls guide which one need to downloads and install for these MC7304 & MC7430 modems ![Screenshot 2024-02-22 214422](https://us1.discourse-cdn.com/flex025/uploads/sierrawireless/original/2X/3/39c9157154a0a2fe353a1a3e7d24dbe39dc90eef.png) ? ---
**Author:** ![AJ23](https://avatars.discourse-cdn.com/v4/letter/a/8491ac/32.png) [@AJ23](https://forum.sierrawireless.com/u/AJ23)\ **Post date:** [February 22, 2024, 4:22pm UTC](https://forum.sierrawireless.com/t/mc7455-usb-device-disconnects-immediately/9415/19 "2024-02-22T16:22:21Z")
If you want I can also provide you the remote access of the server , pls let me know if you want have a look? ---
**Author:** ![jyijyi](https://sea1.discourse-cdn.com/flex025/user_avatar/forum.sierrawireless.com/jyijyi/32/4766_2.png) [@jyijyi](https://forum.sierrawireless.com/u/jyijyi)\ **Post date:** [February 22, 2024, 4:38pm UTC](https://forum.sierrawireless.com/t/mc7455-usb-device-disconnects-immediately/9415/20 "2024-02-22T16:38:13Z")
MBPL\_DRIVERS\_R35\_ENG4-bin.tar is the USB driver MBPL\_SDK\_R35\_ENG4-lite.bin.tar is the SDK BTW, have you read the document? [Next page](https://forum.sierrawireless.com/t/mc7455-usb-device-disconnects-immediately/9415.md?page=2)