Service Forum

[Datenshi]

Hello, I'm an owner of a Lenevo Thinkpad R400 laptop, unfortunately I'm in the situation where i need to recover my supervisor password using hardware. I read the sticky guide in which you mentioned MAX232 chip, the max232 chip is somewhat common in old mobilephone datacables used to communicate with the phone. I've such a cable but not with the MAX232 but with a similar chip called , "OTI 006858" http://forum.se-zone.ru/files/09/04/oti_datasheet_6858_117.pdf Its an USB - RS232 bridge controller and the output from the PCB is an RX,TX and GND wire(TTL level).

My question is, would this be usable instead of the Max232 schematics guide?
Im trying to avoid having to buy new stuff as my town really lack proper electronics shops.


Images of my cable PCB, linked Images are LARGE:

www.fetgrek.com/OTIchipDown.jpg
www.fetgrek.com/OTIchipUP.jpg

oyeah, the driver when installed emulates a regular COM port and the cable shows up as COM3 on my pc.

[victor]

USB2Com usually only emulates RX/TX for serial transfer. BTW, signals are having RS232 logics and not TTL.
The interface used for my software is not making it through RX/TX, in fact is not making a serial RS232 transfer at all, so that cable you have is futile.
_________________
Victor Voinea
ALLservice HQ, Romania.

[Datenshi]

okey, as you can see(above OTIchipUP image) there's a couple of unsoldered spots on the pcb some which are mentioned in the guide i believe, "DTD,DTR,CTS,RTS". Don't know if it makes a difference but i am able to solder onto these...either way if the driver only emulates COM on TX/RX its as you say, futile. Btw isn't TTL level achieved just by lowering the voltage on an RS232 signal? cuz there's a 12,000M resistor between the USB-RS232 chip and the output wires.

Anyway, Thank you Victor for the response.

[victor]

We've tested all USB possible chips and none was 100% a valid solution, USB2COM is maybe ok for standard RX/TX transfer (which often is asynchronic) but not for the I2C interfaces.

If you don't have a PC with built-in serial ports, use a UART PCcard or PCMCIA as it must be a real UART COM port. Build the circuits as per the pdfs coming with R24RF08 kit, and everything would be ok
_________________
Victor Voinea
ALLservice HQ, Romania.

[yourmate]