GL-AR750S (Slate) w/ Sierra Wireless MC7455 (via USB)

Kermee · February 13, 2022, 2:34pm

Hi All,

I’m having a heck of a time getting an MC7455 working via USB to my GL-AR750S to connect to T-Mobile LTE (USA). I’ve been playing with the card configuration in Ubuntu but once I connect it to my GL-AR750S (Slate), it’s not detected by the GUI.

Here is the configuration of the MC7455 so far. It’s loaded with the last GENERIC firmware from Sierra Wireless:

Manufacturer: Sierra Wireless, Incorporated
Model: MC7455
Revision: SWI9X30C_02.24.05.06 r7040 CARMD-EV-FRMWR2 2017/05/19 06:23:09

It’s running the latest version of the GENERIC firmware. I’ve tried USBCOMP=8 and USBCOMP=9 and verified the changes via AT!USBCOMP? then saving it via AT!RESET but neither seem to work. If I run lsusb in shell on the Slate, it’s seen by the system:

Bus 001 Device 002: ID 1199:9071 Sierra Wireless, Inc.

If I unplug and plug it back in, this is what dmesg shows:

[ 701.517250] usb 1-1: new high-speed USB device number 3 using ehci-platform
[ 701.730338] usb 1-1: config 1 has an invalid interface number: 12 but max is 3
[ 701.738144] usb 1-1: config 1 has an invalid interface number: 13 but max is 3
[ 701.745833] usb 1-1: config 1 has an invalid interface number: 13 but max is 3
[ 701.753471] usb 1-1: config 1 has no interface number 1
[ 701.759093] usb 1-1: config 1 has no interface number 2

I know the USB sled I’m using works fine because I have used Quectel EC25-AF’s and EP06-A’s without issue in the same USB sled connected to the Slate.

Any help would be greatly appreciated. I’m sure it’s some configuration I need to do to the MC7455.

Kermee · February 13, 2022, 2:44pm

If it helps, this is the output of lsusb -v -d 1199:9071 from the Slate:

root@GL-AR750S:~# lsusb -v -d 1199:9071

Bus 001 Device 003: ID 1199:9071 Sierra Wireless, Inc.
Device Descriptor:
bLength 18
bDescriptorType 1
bcdUSB 2.10
bDeviceClass 0 (Defined at Interface level)
bDeviceSubClass 0
bDeviceProtocol 0
bMaxPacketSize0 64
idVendor 0x1199 Sierra Wireless, Inc.
idProduct 0x9071
bcdDevice 0.06
iManufacturer 1 Sierra Wireless, Incorporated
iProduct 2 Sierra Wireless MC7455 Qualcomm® Snapdragon™ X7 LTE-A
iSerial 3 LQ81949050041021
bNumConfigurations 1
Configuration Descriptor:
bLength 9
bDescriptorType 2
wTotalLength 167
bNumInterfaces 4
bConfigurationValue 1
iConfiguration 0
bmAttributes 0xa0
(Bus Powered)
Remote Wakeup
MaxPower 500mA
Interface Descriptor:
bLength 9
bDescriptorType 4
bInterfaceNumber 0
bAlternateSetting 0
bNumEndpoints 2
bInterfaceClass 255 Vendor Specific Class
bInterfaceSubClass 255 Vendor Specific Subclass
bInterfaceProtocol 255 Vendor Specific Protocol
iInterface 0
Endpoint Descriptor:
bLength 7
bDescriptorType 5
bEndpointAddress 0x81 EP 1 IN
bmAttributes 2
Transfer Type Bulk
Synch Type None
Usage Type Data
wMaxPacketSize 0x0200 1x 512 bytes
bInterval 0
Endpoint Descriptor:
bLength 7
bDescriptorType 5
bEndpointAddress 0x01 EP 1 OUT
bmAttributes 2
Transfer Type Bulk
Synch Type None
Usage Type Data
wMaxPacketSize 0x0200 1x 512 bytes
bInterval 0
Interface Descriptor:
bLength 9
bDescriptorType 4
bInterfaceNumber 3
bAlternateSetting 0
bNumEndpoints 3
bInterfaceClass 255 Vendor Specific Class
bInterfaceSubClass 0
bInterfaceProtocol 0
iInterface 0
** UNRECOGNIZED: 05 24 00 10 01
** UNRECOGNIZED: 05 24 01 00 00
** UNRECOGNIZED: 04 24 02 02
** UNRECOGNIZED: 05 24 06 00 00
Endpoint Descriptor:
bLength 7
bDescriptorType 5
bEndpointAddress 0x83 EP 3 IN
bmAttributes 3
Transfer Type Interrupt
Synch Type None
Usage Type Data
wMaxPacketSize 0x000a 1x 10 bytes
bInterval 9
Endpoint Descriptor:
bLength 7
bDescriptorType 5
bEndpointAddress 0x82 EP 2 IN
bmAttributes 2
Transfer Type Bulk
Synch Type None
Usage Type Data
wMaxPacketSize 0x0200 1x 512 bytes
bInterval 0
Endpoint Descriptor:
bLength 7
bDescriptorType 5
bEndpointAddress 0x02 EP 2 OUT
bmAttributes 2
Transfer Type Bulk
Synch Type None
Usage Type Data
wMaxPacketSize 0x0200 1x 512 bytes
bInterval 0
Interface Association:
bLength 8
bDescriptorType 11
bFirstInterface 12
bInterfaceCount 2
bFunctionClass 2 Communications
bFunctionSubClass 14
bFunctionProtocol 0
iFunction 0
Interface Descriptor:
bLength 9
bDescriptorType 4
bInterfaceNumber 12
bAlternateSetting 0
bNumEndpoints 1
bInterfaceClass 2 Communications
bInterfaceSubClass 14
bInterfaceProtocol 0
iInterface 0
CDC Header:
bcdCDC 1.10
CDC Union:
bMasterInterface 12
bSlaveInterface 13
CDC MBIM:
bcdMBIMVersion 1.00
wMaxControlMessage 4096
bNumberFilters 32
bMaxFilterSize 128
wMaxSegmentSize 2048
bmNetworkCapabilities 0x20
8-byte ntb input size
UNRECOGNIZED CDC: 08 24 1c 00 01 40 dc 05
Endpoint Descriptor:
bLength 7
bDescriptorType 5
bEndpointAddress 0x85 EP 5 IN
bmAttributes 3
Transfer Type Interrupt
Synch Type None
Usage Type Data
wMaxPacketSize 0x0040 1x 64 bytes
bInterval 9
Interface Descriptor:
bLength 9
bDescriptorType 4
bInterfaceNumber 13
bAlternateSetting 0
bNumEndpoints 0
bInterfaceClass 10 CDC Data
bInterfaceSubClass 0 Unused
bInterfaceProtocol 2
iInterface 0
Interface Descriptor:
bLength 9
bDescriptorType 4
bInterfaceNumber 13
bAlternateSetting 1
bNumEndpoints 2
bInterfaceClass 10 CDC Data
bInterfaceSubClass 0 Unused
bInterfaceProtocol 2
iInterface 0
Endpoint Descriptor:
bLength 7
bDescriptorType 5
bEndpointAddress 0x84 EP 4 IN
bmAttributes 2
Transfer Type Bulk
Synch Type None
Usage Type Data
wMaxPacketSize 0x0200 1x 512 bytes
bInterval 0
Endpoint Descriptor:
bLength 7
bDescriptorType 5
bEndpointAddress 0x03 EP 3 OUT
bmAttributes 2
Transfer Type Bulk
Synch Type None
Usage Type Data
wMaxPacketSize 0x0200 1x 512 bytes
bInterval 0
Binary Object Store Descriptor:
bLength 5
bDescriptorType 15
wTotalLength 12
bNumDeviceCaps 1
USB 2.0 Extension Device Capability:
bLength 7
bDescriptorType 16
bDevCapabilityType 2
bmAttributes 0x00000000
(Missing must-be-set LPM bit!)
Device Status: 0x0000
(Bus Powered)
root@GL-AR750S:~#

alzhao · February 14, 2022, 8:31am

Does it add ttyUSB interfaces at all?

Kermee · February 14, 2022, 8:56am

None. Although I remember seeing a post that I needed to add the ‘qcserial’ package which makes sense because when I use the MC7455 in the USB sled under Ubuntu 20.04, it’s ‘qcserial’ which creates ttyUSB0 through USB2 interfaces. I searched for it in LuCI but couldn’t find which package to add for ‘qcserial’. Granted, I didn’t look very hard.

None are created when plugged into the USB port of the Slate.

Also, quick update. The MC7455 works both under Windows 10 Pro (64-bit) and Ubuntu 20.04 without fuss connecting to T-Mobile (US) LTE. Even Carrier Aggregation works (B4+B12) so not sure why my Slate is having such a tough time with it.

Kermee · February 14, 2022, 9:03am

Duh. It’s this package for “qcserial” isn’t it… qc as in qualcomm.

alzhao · February 14, 2022, 9:05am

Better just to install all related pacakges. I remember it should be the first one.

Kermee · February 14, 2022, 9:08am

Are there any other related packages for the MC7455 other than ‘qcserial’?

I got fed up and put the Quectel EC25-AF back into the USB sled and connected it back to the Slate. I’ll order another USB sled for the MC7455 and try testing again once the new USB sled arrives. Thanks for the help!

Kermee · February 14, 2022, 9:11am

These are the only other two Qualcomm related packages I see that I don’t have installed on the Slate which might apply to the MC7455. The open-plc-utils doesn’t apply to WWAN cards I believe.