chewearn's blog

After installing Debian/NSLU2, I started playing around with the hacked slug. However, after couple of reboots, the slug would get stuck during a boot. I plugged the external USB harddisk to a PC to take a look at the logs. But each time, I discovered that the harddisk has gotten corrupted. Some googling and by trial and error, I was able (most times) to use these commands to recover:

sudo fsck -t ext3 /dev/sdb1
sudo mke2fs -n /dev/sdb1
sudo e2fsck -B 4096 -b 32768 /dev/sdb1

Still, the harddisk kept getting corrupted, and finally I decided it’s time to open up the casing and add a serial port. At the same time, I could de-underclock the slug.

Some careful prying with a plastic tool, and here was the internal board (with the hardware rework already in place at the lower right corner):

Here was the back:

De-underclocking was simply by removing one SMD resistor. The easiest method was to “break” the resistor away. Since I have some soldering skills, I opted to desolder the connection (see photo below). To add the serial port, I cleaned up the soldering thru-holes (using a solder sucker; you got to love the terms used by engineers, no?), then soldered on a 4-pin EH type connector. Here was the closed up of the results:

There was another “trick” needed. The RxD pin of the serial port was unterminated, and could pick up EM noise and cause boot problem. This was easily solved by tying a 10kohm pull-up resistor, adding it between pin 1 and 2:

Finally, I added a serial conversion board. The serial port of the slug was 3.3V logic level, and it should be translated to RS232 logic level. But that is a topic for another post.