NAS Hack: OpenWRT on the MRT StorLink NAS (serial interface converter)

As you saw in my last post, I was not happy at all of the firmware that my new NAS came with.

After playing with it for just one hour, I decided to see which chip it was based on and what was around in terms of hacks and (hopefully) improvements. As I was saying some days ago, I was really happy and excited to find that there's a great guy, LordScaffard, that completed the first porting of OpenWrt for this NAS!

So, of course, I was immediately looking at how to flash my NAS with that OpenWrt flavour. The bad news was that I needed to build an interface. This is because the standard RS-232 interface, which is the common serial interface that there's on the PC, works with logical signal of +12 Volts and -12 Volts that are too high for the serial interface that is on the NAS which is a TTL one. This one is working a + 3,3 Volts signal, so there's the need to use a logical signal converter that may adapt the RS-232 to the right voltage used in the NAS.

I managed to avoid to build such interface last year, when I was working on the Fonera. At that time, I was coding something in OpenWRT and I was flashing quite everyday my Fonera. So I bought the components needed for the serial adapter but I never built it. I was lucky and I flashed sucessfully the Fonera via software, so I didn't needed the serial interface.

So, at least this time I was able to decide to hack the NAS and to hack it really without going out to the electronics shop to buy the components! :o)
Anyway, it requires really few components: 5 capacitors and an integrated circuit!

So, after writing last post, I immediately started to build up my serial interface converter!
I used this electric schematics but I strongly recommand anyone that would like to try to build it to visit also this great page that shows by photo how to setup the converter on a prototyping board. Basically the circuit is using a MAX232 chip which is an integrated circuit that holds all the components to build the converter itself. It needs just some external capacitors to raise up the voltage from the +3,3 Volts to the +12 Volts.

You probably will find so many schematics in the Internet for this converter, and most probably you'll find it with different capacitors values. Basically there are several version of the original MAX232 and some of this version are capable to work with smaller condenser. In my case I used an equivalent chip, the ST232CN, with 5 electrolytic capacitors of 1 micro Farad each (and it worked out perfectly :o).

I followed the same suggestion that I gave you and soldered all the components on a prototyping board: easy and quick! Then I soldered also a DB-9 connector and a jumper connector that I got from an unused chip connector. The DB-9 connector is (of course) needed to connect to the PC's serial interface and the jumper connector is used to connect on the NAS board.

I plugged all together and......nothing worked out!!!
I checked and re-checked all the connections, I was really depressed because after two hours of work I didn't had any result, and, in addition, I didn't had the possibility to change the loosy firmware that was on the NAS!

After several minutes spend in carefully checking all the connections, I discovered that a bast...ehm a very mischievous pin of the chip was bent internally! It was the 16th pin, the Vcc! The pin that is powering up the chip itself! I unbent and inserted it properly with an extreme gentleness, I crossed the fingers and.....voilà!
 
OpenWRT is, of course, working ten times better than the original firmware. The porting by LordScaffard is not at 100%, it still lacks support for some functions and pheripherals. So (this will not sound strange for those who knows me) I immediately wrote him an email and............actually, even if I'm not a real programmer, I'm trying to give him an hand to adapt a more recent Linux kernel for the chip of the NAS!

LordScaffard is incredibly smart in kernel programming, and he's teaching me tons of things. On the other side, I'm trying to do my best, I'm learning really a lot and, of course, I'm enjoying a lot!

I really hope to see the kernel porting completion and, hopefully, to give an acceptable contribution to it. After that, it should be more easy to let all other OpenWRT packages work on this architecture!

Stay tuned!