Virtual COM VPW Interface

This project isn't designed to displace or compete with the UsbVpw but is instead intended to be an alternative and supplemental effort.

The Virtual COM approach provides an alternative to a native USB interface. Compatibility with legacy software applications should be possible, and the learning curve on the PC developers' side will be shortened. A virtual COM port is created using the FTDI FT232RL? chip. Speeds up to 921.6k are supported by USB converter and clocked Atmega micro. Flexibility in terms of adaptation to different micro/firmware packages is also introduced.

The primary elements include the following:

- FTDI FT232RL? USB Serial Converter via USB-B jack
- Atmega8-16AU running at 14.7456 MHz
- Motorola XC68HC58? DLC chip capable of waveshaping and 4x based block modes in VPW via pseudo-SPI interface with Atmega
- Three-channel 10-bit 0-5v A/D inputs via Weidmueller 1615430000 terminal block header
- Standardized generic DB9-male vehicle-side connector for generic OBD2 cable ends
- Fits in readily available Pactec CNS-0407 enclosure
- Only two through-hole components (USB and DB9 connectors)
- Primarily small SMD (0402) components
- Edgecard connection for ISP programming of Atmega8

We haven't written any firmware yet, but it should be no problem. Primary focus should probably be legacy software compatibility and vehicle-side protocol validation.

-- CraigMoates - 25 Dec 2006

• virtualcom_vpw_interface.brd: Eagle 4.16 Board file
• virtualcom_vpw_interface.sch: Eagle 4.16 Schematic file
• readme.txt: Text description of circuit

• Photo of partial first-run assembly for VirtualCom? _VPW unit.: