I bought a Netgear DM111P ethernet modem off ebay recently.  When it arrived, I plugged it in and straight away the power LED -which should be a solid green - went to solid red.  The user manual says this means either the self test is in progress or the self test has failed.  I waited long enough (30+ mins) to confirm the router is bricked.
I would like to reflash the Netgear firmware, however, since the router is bricked I can't use the DM111P's web interface (http://192.168.0.1).

According to this site the DM111P has a TTL serial connector and I've opened up my DM111P and confirmed it has one.  So I thought - rightly or wrongly - with the right hardware I could use a serial console to flash the Netgear firmware to the DM111P.

As the TTL port is 3.3v, I bought this 3.3v-TTL-to-RS232 Serial Converter.  My IBM Thinkpad T40 doesn't have a serial port so I bought this Prolific PL2303 USB-to-Serial adapter to use instead.

The problem now, is that I basically don't know what to do next.
When I plug the Prolific PL2303 into a spare USB port on my IBM Thinkpad T40 (Archlinux), dmesg reports:

:
:
usb 2-2: new full speed USB device using uhci_hcd and address 2
usb 2-2: configuration #1 chosen from 1 choice
usbcore: registered new interface driver usbserial
drivers/usb/serial/usb-serial.c: USB Serial support registered for generic
usbcore: registered new interface driver usbserial_generic
drivers/usb/serial/usb-serial.c: USB Serial Driver core
drivers/usb/serial/usb-serial.c: USB Serial support registered for pl2303
pl2303 2-2:1.0: pl2303 converter detected
usb 2-2: pl2303 converter now attached to ttyUSB0
usbcore: registered new interface driver pl2303
drivers/usb/serial/pl2303.c: Prolific PL2303 USB to serial adaptor driver

and lsmod shows the pl2303 kernel module has loaded:

n00b ~  $  lsmod
Module                  Size  Used by
pl2303                 19076  0 
usbserial              30696  1 pl2303

So, if I understand things correctly, the USB to Serial adapter has been recognised by the kernel and the driver loaded.  dmesg also reports:

n00b ~  $  dmesg | grep tty
console [tty0] enabled
00:0a: ttyS0 at I/O 0x3f8 (irq = 4) is a NS16550A
usb 2-2: pl2303 converter now attached to ttyUSB0

which suggests I should configure minicom (# minicom -s) with /dev/ttyUSB0 rather than /dev/ttyS0.  However - and this is where I'm out of my depth with minicom - when I invoke minicom it comes up with a dialog saying "Initializing Modem".  I don't want to use my Thinkpad T40's modem.  I want to be able to see what the CFE bootloader of my DM111P is outputing once I switch it on, so that I can see what's causing the self test failure.

I don't really understand minicom and couldn't see the configuration options I needed to make.  Can anyone help me out please?  I've never done any serial port work before.

(Last edited by Shagbag on 27 Apr 2008, 08:47)

Try with "minicom -s" and then you can edit the serial port settings (e.g set the port to /dev/ttyUSB0, speed to 115200 8N1).
You can either save then as default or with a name.

If you save different profiles (I have "console" (9600) ,"wrap" (38400), "hspd" (115200)), you can recall them directly on the command line with "minicom hspd", for example.