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Old 08-20-2007, 11:28 PM
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SVXdc SVXdc is offline
Radio wiring harness guru
Subaru Gold Contributor
 
Join Date: Oct 2002
Location: Atlanta, GA
Posts: 615
Significant Technical Input Registered SVX
I'll second Jim's comments.

It would probably be smarter to keep the TTL level signals as short as possible — as close as possible to the ECU. In other words, the MAX232 chip circuit should be right at the ECU plug.

Even if you leave your adapter box as-is, shielded TTL and RS-232 cables may help (if they're not already).

You may be getting additional noise if your laptop is connected to a different power and ground than the ECU (are you using the cigarette lighter jack, perhaps?).


So that USB-to-TTL adaptor (where the chip is inside the USB plug and the long wire is TTL) may not be such a good idea. However, one of the companies has this version that is a USB socket on a little PC board with the tiny chip right underneath it...
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That could be attached to the ECU plug, with a USB A-to-B cable to connect to the laptop.
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1996 Laguna Blue Pearl SVX L AWD
See my home page for SVX radio install/removal instructions and wiring harnesses
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