SIMCOM A7682E - USB interface

[BlueMixx]

I have a SIMCOM A7682E module connected to a Raspberry Pi CM4 via the USB interface.

The connection between the CM4 and SIMCOM works perfectly, and I can communicate (send and receive AT commands) with the SIMCOM via Minicom on ttyUSB1 from the CM4. However, when I disconnect the antenna cable for a few seconds and then try to send AT commands to the SIMCOM, it doesn't work—I can't even type in the Minicom console.

It's almost as if the SIMCOM or the CM4 does not want to allow communication to the SIMCOM. This only happens when the internet disconnects, and after a few seconds, the USB interface freezes.

Any suggestions on how to fix this?

 

[aliarifat794]

Can you check the kernel messages after the USB interface freezes?

 

[BlueMixx]

Can you check the kernel messages after the USB interface freezes?

[Jun21 13:52] usb 1-1: new high-speed USB device number 3 using xhci-hcd
[  +0.160967] usb 1-1: New USB device found, idVendor=2ecc, idProduct=3004, bcdDevice= 0.00
[  +0.000011] usb 1-1: New USB device strings: Mfr=1, Product=2, SerialNumber=3
[  +0.000005] usb 1-1: Product: Arom Usb Boot Port
[  +0.000004] usb 1-1: Manufacturer: ASR Microelectronics
[  +0.000004] usb 1-1: SerialNumber: arom0123456789
[  +0.015112] cdc_acm 1-1:1.0: ttyACM0: USB ACM device
[  +0.422015] usb 1-1: USB disconnect, device number 3
[  +5.321902] usb 1-1: new high-speed USB device number 4 using xhci-hcd
[  +0.148191] usb 1-1: config 1 has an invalid interface number: 5 but max is 4
[  +0.000020] usb 1-1: config 1 has no interface number 3
[  +0.000247] usb 1-1: New USB device found, idVendor=1e0e, idProduct=9011, bcdDevice= 1.00
[  +0.000017] usb 1-1: New USB device strings: Mfr=1, Product=2, SerialNumber=3
[  +0.000012] usb 1-1: Product: A76XX Series LTE Module
[  +0.000009] usb 1-1: Manufacturer: SIMCom Wireless Solution
[  +0.000009] usb 1-1: SerialNumber: 200806006809080000
[  +0.161988] usbcore: registered new interface driver cdc_ether
[  +0.004544] usbcore: registered new interface driver usbserial_generic
[  +0.000057] usbserial: USB Serial support registered for generic
[  +0.013264] rndis_host 1-1:1.0 usb0: register 'rndis_host' at usb-fe9c0000.xhci-1, RNDIS device, ae:0c:29:a3:9b:6d
[  +0.000688] usbcore: registered new interface driver rndis_host
[  +0.007773] usbcore: registered new interface driver option
[  +0.000055] usbserial: USB Serial support registered for GSM modem (1-port)
[  +0.001588] usb 1-1: GSM modem (1-port) converter now attached to ttyUSB0
[  +0.002896] usb 1-1: GSM modem (1-port) converter now attached to ttyUSB1
[  +0.000766] usb 1-1: GSM modem (1-port) converter now attached to ttyUSB2
[Jun21 15:42] usb 1-1: USB disconnect, device number 4
[  +0.000211] rndis_host 1-1:1.0 usb0: unregister 'rndis_host' usb-fe9c0000.xhci-1, RNDIS device
[  +0.043447] option1 ttyUSB0: GSM modem (1-port) converter now disconnected from ttyUSB0
[  +0.001942] option1 ttyUSB1: GSM modem (1-port) converter now disconnected from ttyUSB1
[  +0.000418] option1 ttyUSB2: GSM modem (1-port) converter now disconnected from ttyUSB2
[  +0.878942] usb 1-1: new high-speed USB device number 5 using xhci-hcd
[  +0.164959] usb 1-1: New USB device found, idVendor=2ecc, idProduct=3004, bcdDevice= 0.00
[  +0.000019] usb 1-1: New USB device strings: Mfr=1, Product=2, SerialNumber=3
[  +0.000006] usb 1-1: Product: Arom Usb Boot Port
[  +0.000004] usb 1-1: Manufacturer: ASR Microelectronics
[  +0.000003] usb 1-1: SerialNumber: arom0123456789
[  +0.009130] cdc_acm 1-1:1.0: ttyACM0: USB ACM device
[  +0.421131] usb 1-1: USB disconnect, device number 5
[Jun21 15:43] usb 1-1: new high-speed USB device number 6 using xhci-hcd
[  +0.148129] usb 1-1: config 1 has an invalid interface number: 5 but max is 4
[  +0.000018] usb 1-1: config 1 has no interface number 3
[  +0.000263] usb 1-1: New USB device found, idVendor=1e0e, idProduct=9011, bcdDevice= 1.00
[  +0.000008] usb 1-1: New USB device strings: Mfr=1, Product=2, SerialNumber=3
[  +0.000005] usb 1-1: Product: A76XX Series LTE Module
[  +0.000004] usb 1-1: Manufacturer: SIMCom Wireless Solution
[  +0.000004] usb 1-1: SerialNumber: 200806006809080000
[ +20.723881] rndis_host 1-1:1.0 usb0: register 'rndis_host' at usb-fe9c0000.xhci-1, RNDIS device, ae:0c:29:a3:9b:6d
[  +0.000818] usb 1-1: GSM modem (1-port) converter now attached to ttyUSB0
[  +0.000227] usb 1-1: GSM modem (1-port) converter now attached to ttyUSB1
[  +0.001314] usb 1-1: GSM modem (1-port) converter now attached to ttyUSB2