Cannot connect to the usb-serial port (GSM modem) - linux

Question

I've decided to bring up a GSM Modem for my Linux machine (OpenSuse 12.1 64-bit on Vmware) so that I can use it as the SMS gateway. I've got a Wavecom M1306B GSM modem which provides a USB interface, and obviously there is a USB cable (end to end, GSM Modem to my Desktop) with it.
I tested this modem successfully with my Windows 7 64-bit PC by running some basic commands on it. (like: AT , ATZ, ..)
Here are some of my logs:
machine2:~ # lsusb
Bus 001 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 001 Device 002: ID 0e0f:0003 VMware, Inc. Virtual Mouse
Bus 001 Device 003: ID 0e0f:0002 VMware, Inc. Virtual USB Hub
Bus 001 Device 006: ID 067b:2303 Prolific Technology, Inc. PL2303 Serial Port
lsusb -v output for that interface:
Bus 001 Device 006: ID 067b:2303 Prolific Technology, Inc. PL2303 Serial Port
Device Descriptor:
bLength 18
bDescriptorType 1
bcdUSB 1.10
bDeviceClass 0 (Defined at Interface level)
bDeviceSubClass 0
bDeviceProtocol 0
bMaxPacketSize0 64
idVendor 0x067b Prolific Technology, Inc.
idProduct 0x2303 PL2303 Serial Port
bcdDevice 3.00
iManufacturer 1 Prolific Technology Inc.
iProduct 2 USB-Serial Controller
iSerial 0
bNumConfigurations 1
Configuration Descriptor:
bLength 9
bDescriptorType 2
wTotalLength 39
bNumInterfaces 1
bConfigurationValue 1
iConfiguration 0
bmAttributes 0xa0
(Bus Powered)
Remote Wakeup
MaxPower 100mA
Interface Descriptor:
bLength 9
bDescriptorType 4
bInterfaceNumber 0
bAlternateSetting 0
bNumEndpoints 3
bInterfaceClass 255 Vendor Specific Class
bInterfaceSubClass 0
bInterfaceProtocol 0
iInterface 0
Endpoint Descriptor:
bLength 7
bDescriptorType 5
bEndpointAddress 0x81 EP 1 IN
bmAttributes 3
Transfer Type Interrupt
Synch Type None
Usage Type Data
wMaxPacketSize 0x000a 1x 10 bytes
bInterval 1
Endpoint Descriptor:
bLength 7
bDescriptorType 5
bEndpointAddress 0x02 EP 2 OUT
bmAttributes 2
Transfer Type Bulk
Synch Type None
Usage Type Data
wMaxPacketSize 0x0040 1x 64 bytes
bInterval 0
Endpoint Descriptor:
bLength 7
bDescriptorType 5
bEndpointAddress 0x83 EP 3 IN
bmAttributes 2
Transfer Type Bulk
Synch Type None
Usage Type Data
wMaxPacketSize 0x0040 1x 64 bytes
bInterval 0
Device Status: 0x0000
(Bus Powered)
machine2:/proc # setserial -a /dev/ttyUSB0
/dev/ttyUSB0, Line 0, UART: 16654, Port: 0x0000, IRQ: 0
Baud_base: 460800, close_delay: 0, divisor: 0
closing_wait: infinte
Flags: spd_normal
machine2:/home/smsto/bin # setserial -a /dev/ttyS0
/dev/ttyS0, Line 0, UART: 16550A, Port: 0x03f8, IRQ: 4
Baud_base: 115200, close_delay: 50, divisor: 0
closing_wait: 3000
Flags: spd_normal skip_test
machine2:/home/smsto/bin # setserial -a /dev/ttyS1
/dev/ttyS1, Line 1, UART: 16550A, Port: 0x02f8, IRQ: 3
Baud_base: 115200, close_delay: 50, divisor: 0
closing_wait: 3000
Flags: spd_normal skip_test
machine2:/proc # setserial -G /dev/ttyUSB0
/dev/ttyUSB0 uart 16654 port 0x0000 irq 0 baud_base 460800 spd_normal
machine2:/proc # setserial /dev/ttyUSB0
/dev/ttyUSB0, UART: 16654, Port: 0x0000, IRQ: 0
machine2:/proc/tty/driver # ls -ltr
total 0
-r--r--r-- 1 root root 0 Jan 10 14:03 usbserial
-r--r--r-- 1 root root 0 Jan 10 14:03 serial
machine2:/proc/tty/driver # cat serial
serinfo:1.0 driver revision:
0: uart:16550A port:000003F8 irq:4 tx:0 rx:0 CTS|DSR|CD
1: uart:16550A port:000002F8 irq:3 tx:0 rx:0 CTS|DSR|CD
2: uart:unknown port:000003E8 irq:4
3: uart:unknown port:000002E8 irq:3
4: uart:unknown port:00000000 irq:0
5: uart:unknown port:00000000 irq:0
6: uart:unknown port:00000000 irq:0
7: uart:unknown port:00000000 irq:0
machine2:/proc/tty/driver # cat usbserial
usbserinfo:1.0 driver:2.0
0: module:pl2303 name:"pl2303" vendor:067b product:2303 num_ports:1 port:1 path:usb-0000:02:00.0-2.1
machine2:/proc/tty # cat drivers
/dev/tty /dev/tty 5 0 system:/dev/tty
/dev/console /dev/console 5 1 system:console
/dev/ptmx /dev/ptmx 5 2 system
/dev/vc/0 /dev/vc/0 4 0 system:vtmaster
usbserial /dev/ttyUSB 188 0-253 serial
serial /dev/ttyS 4 64-79 serial
pty_slave /dev/pts 136 0-1048575 pty:slave
pty_master /dev/ptm 128 0-1048575 pty:master
unknown /dev/tty 4 1-63 console
machine2:/proc/tty # dmesg | grep -i tty
[ 1.383652] serial8250: ttyS0 at I/O 0x3f8 (irq = 4) is a 16550A
[ 1.424541] serial8250: ttyS1 at I/O 0x2f8 (irq = 3) is a 16550A
[ 1.581063] 00:0a: ttyS0 at I/O 0x3f8 (irq = 4) is a 16550A
[ 1.654207] 00:0b: ttyS1 at I/O 0x2f8 (irq = 3) is a 16550A
[ 1.938507] tty tty17: hash matches
[ 2498.137304] usb 1-2.1: pl2303 converter now attached to ttyUSB0
I noticed that the Baud rate of USB0 interface is too much, so i tried to assign 115200 :
machine2:/proc # setserial /dev/ttyUSB0 baud_base 115200
Cannot set serial info: Invalid argument
So, it is the problem ... and I receive this error.
Whenever I try to connect S0, S1, USB0 interfaces via minicom, it simply doesn't work.

Answer 1

Baud_base is not the port speed, it's the maximum speed when a frequency divisor is 1. The ability to set baud_base probably doesn't apply to USB serial device at all, and it's most certainly not what you want.
Use stty to set the port speed, or use cu or minicom for testing (they can set port speed by themselves).

Answer 2

I'm not sure about the baud rate but If you open up another terminal and do cat /dev/ttyUSB0
Then in the first terminal do echo AT > /dev/ttyUSB0 you might get an OK back..not sure if it helps but it should get you a response at least..