Purpose: to be able to simulate different devices attached to the IEBus.
Complete schematic of the emulator is here.
Toyota uses the IEBus standard for internal equipment to communicate. As far as it is almost impossible to buy the IEBus driver IC it is possible to simulate it on a uController. The uController shall be fast enough to process the bus signal impulses that are less then 3 uSec. And at the same time the uController shall be fast enough to send received and processed data to the host computer in less then 120-130 uSec so the next message on the bus is not lost.
The uController of choice is pic18f2550. It contains the USB 2.0 module which supports full speed communication mode and can principally work up to 48MHz. It also contain 2 internal comparators that can be used to receive signal from the bus (though it was decided to use an external comparator to separate the uController from the bus). Device is supported by the PICmicro 18Cxx C compiler so it is possible to write the firmware in C. I'm using compiler version 2.40.
Complete schematic of the emulator is here.
