RS232 <-> K-line

cmartinez

Joined Jan 17, 2007
8,218
Can any one share RS232 - K line converter schematic.
I do see a schematic in the following link, but i see them using +12 and -12V.

http://blog.perquin.com/blog/category/odbii/

Any simple schematic you have which you can share?

thanks
jis
From Wikipedia:
  • ISO 9141-2. This protocol has an asynchronous serial data rate of 10.4 kBaud. It is somewhat similar to RS-232; however, the signal levels are different, and communications happens on a single, bidirectional line without additional handshake signals. ISO 9141-2 is primarily used in Chrysler, European, and Asian vehicles.
    • pin 7: K-line
    • pin 15: L-line (optional)
    • UART signaling
    • K-line idles high, with a 510 ohm resistor to Vbatt
    • The active/dominant state is driven low with an open-collector driver.
    • Message length is Max 260Bytes. Data field MAX 255.
Apparently you NEED to have +12V and -12V signals in order to comply with the single-line bidirectional protocol. I doubt the circuit shown in your link could get any simpler than that. It's really not that difficult to make a small -12V power supply, but if you want a hassle-free circuit, I suggest you use a DC-DC converter like this one.
 
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