Aw: Jeffs Interface - Loopback Test

Hi,

Summary of some older mails:
Cut the connection between pin 7 (RTS) of the RS232-connector
(PC side) and the adapter. Tie this pin to ground.

Connect the adapter to your laptop.

Connect a 12V power supply to the power/ground pins of the
OBD-II side of the adapter. Do not connect the adapter to your
car. The K- and L-lines remain unconnected.

Run a terminal program like Hyperterminal, with flow control
disabled, full duplex, direct connect to com1, 19200 bps.
Anything you type should echo back to the screen. If not,
something is wrong with your adapter.

Check 38400 bps also. If it misses or changes characters, your
laptop may have insufficent voltage (check the +/- ranges with
a voltmeter), or your optoisolators may not have sufficent
bandwidth. If the notebook has output voltages significently
lower than +-5V try to lower the 1K-resistances in series with
the diodes of the optoisolator.

Disconnect the adapter from the laptop and the 12V supply.

Reestablish the original connection between RS232 pin 7 and the
adapter. This connection had to be removed only for test.

This is a loopback over the K-section of the adapter, it does
not test the L-section.

If the adapter does not work try to connect DCD, DTR and DSR
together (pins 1, 4 and 6 of the RS-232 interface). See my
hints in mail number 65 of this discussion group.

Have fun!
Arnold

 
Received on Fri Oct 06 06:51:18 2000