A USB to SDL Interface

The Serial Data Link (SDL) is a diagnostic interface that allows fault codes and real time data to read from the ECU. This interface is very rarely referred to in documentation for early models but is sometimes shown on the schematic. There are two different connectors used, a 12-pin ALDL style connector and a 16-pin J1962 (OBD2) connector. If you have the ALDL connector then I recommend changing it to the J1962, these can be picked up very cheaply new or used. The ALDL connector is harder to source and more expensive.

The interface is very similar to the ALDL interface used on older GM vehicles, however the voltage thresholds and software protocols are different. Although some people have had success with home built and commercially available ALDL interfaces some of the circuits available are extremely poor and could lead to damage of your ECU or PC/Laptop. An automotive power source is extremely noisy and unstable and special precautions need to be taken when designing equipment for a vehicle.

The RhinoPower Interface

Here I describe an interface that I have designed specifically for Suzukis. This interface uses automotive quality components and is designed to meet the current automotive standards of most countries. In addition I have paid particular attention to ensuring that the voltage thresholds are correct, that there is adequate isolation of the PC/laptop and that it is robust enough to survive the worst power supply conditions (load dump). The interfaces uses a USB connection to the PC, the serial port favoured by some people is long since obsolete and often cannot support the odd baud rates used by the SDL.

The interface is small enough to fit into a short (the cheapest type!) J1962 backshell as shown below:







The schematics can be downloaded Here.

This interface has been tested on several ECUs, it uses an industry standard FTDI UART chip, this needs to be configured to invert the RX pin, a utility is available on the FTDI Website.