Viewing kernel messages the hard way..

When searching over the file system of the Trendtac (with Firefox/Bon Echo using file:///) I stumbled upon a file called cmdline in which the following was written:

mem=128M console=ttyS0,115200n8 root=/dev/ssfdca1 rw noatime

This means the console output is directed to a serial port named ttyS0 but the odd thing is there is no 'real' serial port on the Trendtac

Inside the EPC700 mini laptop, accessible through the battery compartment is a small 4 pin connector (J502).
It is probably used as a programming connector during production but it also emulates a simple serial port for console output. You can see it on this photo: serial port connector

The connectors pin connection is as follows:

• (1) +5 Volt
• (2) TX Data (out)
• (3) RX Data (in)
• (4) GND

If unsure which is which, check with a multimeter against a known ground (the metal frame of one of the USB ports for example).

Since the signals TX and RX data are at TTL/CMOS levels and not suitable for direct connection to a real RS232 port, you need to convert the signals with a TTL to RS232 converter like the MAX232(A) or compatible.

This my homebrew adapter cable: TTL to RS232 adapter

The schematic is found here: Schematic

The converter is meant to be used with a so-called null-modem cable, of you don't have such a cable just exchange the pins 2 and 3 on the SUBD-connector and use a straight cable. To test the console port I hooked up the Trendtac to my main (Kubuntu) Linux PC and installed a program called minicom The serial settings for minicom are 115200 baud 8 bits with no handshake signals. With minicom active I switched on the Trendtac and behold: kernel messages !

After the Trendtac booted up to the desktop the messages in minicom ended with 'Press Enter to activate this console' and after pressing Enter I had root access !

From here on it was rather easy to enable the telnetd in /etc/init.d/Start and after that I could log in over the network too.

-- Gert vd Knokke - 15 Aug 2008

Connectors and stuff

The connector seems to be an SR connector. It is used in some hardware like this: ACT-DSL-BUS cable or another. You can use the cable and something like this to build a usb->trendtac serial console cable. For the usb cable you can also use a 2.5 euro usb->serial cable for mobile phones. Getting the SR connector is probably the most expensive . PS: I have yet to get confirmed that the conrad cables are indeed correct.