We offer a variety of interfaces to hook your PC up to your car. Whether you would like to build your own or settle for a fully tested professional interface, find what you want here!
There are two main types of interfaces available, basic "dumb" interfaces and intelligent ELM327 interfaces.
The "dumb" interfaces can be used with VAGCOM v409, AlfaDiag, VOL-FCR and others. They are available in RS232 or USB versions. Most software nowadays can drive the USB versions just fine; however, there can be some compatibility problems if the programmer chooses unsupported baud rates or if a particular ECU requires quite tight timing. This is because an RS232 port has what's called a UART which the programmer has direct control over. When an USB interface is plugged in, the UART is a virtual one (emulated by the driver) that sits on the Universal Serial Bus, therefore the precise timing needed by some ECUs cannot be achieved accurately if the operating system (i.e. Windows) decides to schedule something else on the bus. Saying all that, PCs and Laptops are so fast nowadays and ECUs are less time critical, therefore the chances of any problems are greatly reduced.
Where this RS232 vs USB problem doesn't exist is when the interface is "intelligent". We mean intelligent when we talk about interfaces with their own CPU on board, i.e. the ELM327. This is a custom programmed PIC processor which has all of the OBD-II VPW, PCM, CAN-BUS protocols programmed on chip. The ELM327 sets up the communication with the appropriate OBD-II protocol and basically waits for simple commands to come from the host PC/Laptop. This makes the task of writing the OBD-II application much more simpler because the programmer doesn't need to worry about any of the ECU's housekeeping (wake-up, timeouts, handshaking, etc).
The ELM327 based interfaces come in 3 flavours - RS232, USB and Bluetooth. By far the most efficient interface is the USB one because it communicates at 38,000 baud over the very fast USB interface. The 2nd most efficient is the RS232 version but you'll notice the CPU loading may increase slightly due to the operating system having to service the serial UART. Unfortunately, the least efficient version is the Bluetooth interface BUT it is the most convenient! It's the least efficient because it has to run at 9,600 baud because of the limitations of Bluetooth. However, unless you're logging a huge amount of data I don't think this will be a problem - especially when you can load some OBD-II software onto your Windows Mobile device and have a fully portable scanner in your pocket!