IEBus Controller – Design

Now to outline some design requirements for myself to get started with the IEBus.

Design Requirements

  1. Microcontroller doing IEBus communicates using UART to the planned navi unit in an asynchronous fashion. Browsing the thread in Acurazine indicates the Honda Navi will broadcast packets on button and touch screen press automatically.
  2. Make the circuit reusable between a standalone circuit for debug and a embedded circuit that will become part of the navi board.
  3. Microcontroller must be able to process and acknowledge at least mode 1 messages correctly
  4. Microcontroller’s UART interface must be at 3.3V levels
  5. ESD protection is required on IEBus connections to the car

The easiest approach to me is to use an 8-bit microcontroller to process and handle the IEBus. My immediate pick is an Atmel ATXMEGA32E5, an AVR 8-bit microcontroller. It can run 32 MHz which should be enough to handle up to mode 2 communication and is low power off a 3.3V. The companion to this chip in the standalone circuit will be an Atmel SAM3X which is an ARM and will provide an USB interface to the xmega chip. The communication between the SAM3X and the XMEGA will be the asynchronous UART protocol I hope to have in the larger microprocessor navi unit.

I attached a quick diagram of what I envision.


  • Chris Fairhall

    How’s this project going? Haven’t seen an update in a while.