First real look at my SBC

My 7390 SBC Front View

My 7390 SBC Front View

Rear View

Rear View

So today I decided to take out my single board computer that I purchased for my project. It is the TS-TPC-7390. More details can be seen here.

Starting the device required me to wire in the transformer that came separate, but apparently it is important to get the polarity correct as there is no safety circuit on the board!? – Amn’t convinced with such an expensive device not having such features but I amn’t willing to find out either!

The device boots up to a Linux GUI in around 1.5 seconds as they claim with a nice start up tune and Technologic Systems logo. The desktop environment is IceWM, which is light weight. Obviously a big one like KDE would not work in such a device with the limited storage and memory capacity.

I was hoping the response from the touch screen would be a bit better as it requires quite bit of pressure on it to get an interaction. I tapped on the start button of IceWM and navigated around to have a look at what was available on the device. Nothing really that fancy, firefox was about the most compicated thing there and that didn’t even load! – It is actually Iceweasal – another version of firefox without all the proprietary logos etc so its free to ship. In the System Utilities folder, there was a Virtual Keyboard which is quite useful for input but really slow to use. Unfortunetly don’t have a USB keyboard with me so decided I had to figure another way of interacting with this device!

On the documentation it says that the device is preconfigured with IP address of 192.168.0.50, so I set my computer in the same subject range and attempted to telnet into it. It worked no bother and no root password either! Doing a uname -r, it is clear that it is Debian linux that is running on the device, Debian Etch to be percise. An issue of free command confirmed that 64MB ram was actually on this device with about 15MB free, but most of this is taken up by the WM which I won’t have in my project.

An 2GB SD card comes with the SBC (plugged into its slot) which contains images of Linux and a whole ready made cross complimation setup using Eclipse. This card can be hot swapped unlike CF so I took it out and stuck it into my card reader to have a look to see what was on it. It was not readable by 2 of my card readers both on different PCs so I thought something up so. At first I thought it must be because a none native Windows FS but this didn’t make since since Eclipse on it was one for Windows. I stuck it into my SBC again to see if I could read it from Linux. Doing a ls on /dev I could see sdcarddata, sdcarddata1 – sdcarddata4. This suggested to me that there was 4 partitions on the device and looking at the documentation I confirmed this. The first was a 1.5Gig that contains all the files I am looking for so I created a mount folder /mnt/donal/ and mounted the SD card using the command mount /dev/sdcarddata1 /mnt/donal -t vfat. This worked fine and I could view the contents.
I tried taring the whole folder but no room!. I set up a FTP server on my laptop and tried pushing items across. This worked fine for individual files but I wanted recursively to do everything but this doesn’t work with the standard ftp utility in Linux. Next option was SCP so I set up a SSH server on my computer creating an account for the SBC. I could successfully send all files to a home folder on my laptop using the command scp -r * donal@192.168.0.50:/ This transfer took almost 30 minutes but finally I got everything I wanted.

The next thing I was interested in looking at was connecting to the device using a serial connection. Looking at the inittab file, it writes the Kernel output to /dev/ttyAM0 which is the console port of this device. This is accessible by connecting a JTAG board to the SBC’s JTAG connector. I used a null modem cable then from that to my laptop and set the correct settings on hyperterminal (115200, 1S No Parity, 8Data No F/C). I got an output to hypterminal and could enter commands to the shell prompt. Least now I know my USB->Serial adapator works but there are issues with these when timing is involved due to the extra abstraction hardware layer associated with USB.

There were 2 more ports, COM1 and COM2 available on the board. I connected the Serial adapator to the pin outs on the board for COM1 and connected to the null modem. I hadn’t a clue of the baud rate etc for it so I guessed 9600 with the standard 8N1 & no F/C. So how would I test it? – There are no terminal utilities on the SBC. So what i thought of was doing a simple echo and redirecting it to /dev/ttyAM1 so I issued the command echo “Hi Donal!\r” > /dev/ttyAM1 and this worked perfectly so now I know my ports are working.

I created a file using touch hello but the file wouldn’t remain after a restart which suggested to me the NAND Flash was read only. This also lead me to believe there was no swap file and I confirmed this too. This is why firefox froze when loaded I’m guessing! – I will have to investigate if possible to mount a partition from a SD card and link a SWAP to this device. However, will 6MB/S be fast enough I don’t know! – Either way I am going to use the SD card for writing settings and logging data from Automon.

I think that was enough messing with the SBC for now, next I will have to look at how to get QT on it or even re compile a smaller debian image with QT/Extended binaries installed. I think that may be something that I’ll do later down the road though.

Wednesday, January 14th, 2009 Single Board Computer

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