DIY cable problems

[aliman]

Does anyone know if the schematic from Tech Edge, using the MAX 232 is correct. I read in a post someone had mentioned that diode D3 was incorrect.
I built the circuit as shown in their schematic, and I was using EFILive V4 to try and connect to my 1989 5.7L IROC-Z.
I have connected the Tech-Edge circuit to the ALDL connector via home built cable, and the Tech-Edge circuit through a Serial to USB adapter cable made by Prolific Corp. to a Toshiba laptop.
I can't get it to connect ?
Any help would be great !

Aliman
Here is what I'm seeing when I try and connect

1:12.035: Initialising...
21:12.597: Opening COM3 8228,8,N,1
21:12.718: Ready.
21:18.632: Check vehicle interface...
21:18.639: Waiting for Aldl bus silence of at least 50ms...
21:18.687: Requesting Max232 interface to acknowlege: $FF,$55,$AC...
21:18.796: Com timeout: Expecting frame header byte
21:18.800: No response from Max232
21:18.800: Retrying Max232 detection...

21:18.800: Waiting for Aldl bus silence of at least 50ms...
21:18.847: Requesting Max232 interface to acknowlege: $FF,$55,$AC...
21:18.956: Com timeout: Expecting frame header byte
21:18.962: No response from Max232
21:18.962: Retrying Max232 detection...

21:18.962: Waiting for Aldl bus silence of at least 50ms...
21:19.011: Requesting Max232 interface to acknowlege: $FF,$55,$AC...
21:19.120: Com timeout: Expecting frame header byte
21:19.126: No response from Max232
21:19.126: Retrying Max232 detection...

21:19.126: Interface cannot be detected

21:19.153: Scanning for heartbeat and chatter frames...
21:19.153: Waiting for Aldl bus silence of at least 50ms...
21:19.303: Com timeout: Expecting frame header byte
21:19.307: No chatter found

[ahmed]

check the com port number for usb to serial adapter , it should be the same as efilive software

[joecar]

Hi Ahmed, welcome to the forum :cheers:

What vehicle do you have...?

[ahmed]

hi joecar
i've honda civic 93

[Blacky]

Most USB-Serial adapters are not capable of generating the correct baud rate required for ALDL communications. The baud rate required in 8192 baud. A Real PC UART chip controlling a real RS232 serial port is capable of generating a baud rate of 8228 which is close enough to 8192 to allow it to work. I recommend using a real serial port, you may need to get your desktop computer (if it has a serial port) close to your vehicle to test whether the cable works using a real serial port. If it does then you can be pretty confident that the Serial-USB converter is not generating the correct baud rate.

Regards
Paul

[ahmed]

Hi Blacky
the usb to serial converter works good and the Tech Edge circuit is correct
I had made it and used it with usb to serial converter and everything is good
now i'm making a circuit to connect aldl to usb directly