Description
Getting serial connection (5v RS232) from a USB SEMC DSS-20 SyncStation
Features
- Disassembly
- Attaching serial communication cables
- Remove serial EEPROM to avoid custom drivers
- Stripping down the PCB for minimal size
Development
During my time as concept creator at Sony Ericsson I saved some SyncStations from being thrown away.
These docking stations were made to allow a modern computer with USB connector to be attached to phones that had the older serial interface on the system connector. The SyncStation is easy to open, just use a ph0 screwdriver to remove three screws.
On the main PCB the main component is a FTDI FT232BM. All you need to do is to attach RX and TX cables to pi 24 and 25 (the upper right corner). I connected the gnd to the black USB cable and Robert is your mother’s brother – you now have a USB to serial adapter. For this adapter you need to use special SEMC DSS-20 SEMC drivers. You can just google it and download them to get the virtual serial port to work. Another way is to cut off the lines to the serial EEPROM or simply remove the chip. This turns the SyncStation to a standard USB to serial bridge and you can use the drivers that are included in most operating systems. To make the PCB more stable I de soldered the system connector and secured the USB cable with a zip tie.
Here is the Pinout for the common pins on the FT232BM chip:
| Pin | Function |
| 25 | TxD |
| 24 | RxD |
| 9/17 | GND |
| 3/13/26 | VCC |
| 23 | RTS |
| 22 | CTS |
Hi
I was able to convert a dss-20 to a normal USB Serial Converter by reprogramming the e-prom using ft_prog from FTDI. Thanks for a good project that I could use as a fall-back if my programming efforts failed.
BR Erling
Definitely a more sophisticated approach then my brute force method of removing the chip ;)
Thanks for the tip!
Hi Erling
I tried using ft-prog on a dss20. But the program didn’t discover the ftdi chip during the initial “F5” scan. Do you have any secret trick?
I guess i could clear the eeprom first using a buspirate, but that is a bit overkill…
I didn’t try with SE drivers, I installed FTDI’s driver right away via device manager – you’ll have to play with driver selection to find out which one will work because I don’t remember anymore. That way I was able to reprogram it.
as far as i know, ft-prog will only recognize devices that are already handled by the ftdi driver (hen and egg problem.)
you first have to modifiy the driver’s inf-file to add the device’s OLD id,
then the ftdi driver will regognize it, THEN you can use ft-prog to change the id.
yes, this is silly.
Thanks for the input – I guess a software fix is a bit easier then removing a small SMD chip (and you have the option to use the eeprom for custom settings of the ft-prog)
Nice work!
/j
Hi Johan
I did have some problems to get it to work, drivers etc and I had to reboot the PC a few times. I have another usb to serial port that I used as areference to see that I could access it and then it worked with the dss20 also. But it was long time ago so I may have missed something.
Great find, a relatvely expensive FTDI chip in a dock which is probably a $few on evilbay. One thing – the FTDI chip gives 5V TTL serial, not RS232. The latter uses different levels – you can’t connect TTL serial to RS232 without a converter like a MAX232 or some clever transistor based level shifting circuit. I guess you know this already, it just isn’t clear in your post.
You are absolutely correct. Thank you for the clarification!
If you need a more compact solution I have made a custom PCB for this chip:
http://vonkonow.com/wordpress/2012/03/usbserial-pcb/
one thing i am missing in your post:
the dock has some circuitry connected to the ftdi’s tx/rx already
(i found your post searching for information on that circuitry).
the ftdi’s is NOT directly connected to the unused dock connector.
so that _should_ be disconnected to avoid problems.
imagine some output is connected to the ftdi’s Rx input,
when you connect another in parallel, you might end up with a short-circuit or other fun…
it appears that Rx is connect to pin 4 of the HCT175, which is an output…
just noticed, pin 4 is an input… but still
Gr8, thnx!
I have used the dock without removing the HCT175 and it works fine, but I guess removing it doesn’t hurt…
(to be extra clear – I did connect rx/tx directly to the ftdi, not to the dock connector)
/j
ofcourse you did..
but still there’s all this logic on the board and we have no idea how it’s wired…
i’d prefer to
– find out what it does (i’d expect somebody who worked at sony ericsson to know! ;) )
– remove it
– ideally chop off the board to make it smaller
– (making a new board with just the ftdi is impractical)
rotfl
Yes, I guess I should be able to get that info… (they closed the site a couple of years ago on top of that; the docking station itself isn’t really new, ill see if I can get any info somehow…)
I really suspect it is just buffers to prevent damage to either the phone or the computer.
If you try to chop it off, let me know how it goes ;)
/j