AVT-715 - A Dual J1850 Interface (VPW and PWM)
J1850 Vehicle Networks
SAE standard J1850 is gaining widespread acceptance by the automobile manufacturers. With the advent of this new network architecture engineers, technicians, and others need to be able to test, monitor, and communicate with a J1850 network equipped vehicle.
Complicating this issue is the fact that a J1850 network may be implemented in either of two incompatible versions: Variable Pulse Width (VPW) or Pulse Width Modulation (PWM).
The AVT Solution
The AVT-715 Dual J1850 Interface is a software and hardware package that allows the user to connect a personal computer to a J1850 equipped vehicle. With this package a user can connect to a J1850 bus and monitor network traffic, log network activity, analyze communications, simulate a network node, and perform a number of other network functions.
By combining the interface functions for both VPW and PWM modes into a single unit the investment by the user is reduced. Similarly, the control software is designed for operation on a standard PC, such as a laptop.
The AVT-715 is available as a ready to use package or as an OEM module only.
The AVT-715 Controller Software
The AVT-715 controller software can operate in a command mode which permits operator introduction of network messages onto the J1850 bus. This mode permits the testing of node interactions to specific message sequences and other user defined test scenarios. Commands can be entered individually or downloaded via a batch file.
A network monitor mode permits the capture and display of bus traffic. Options to timetag and log the data to a file ensures an historical record of network activity for later analysis. The disk logging function is limited only by the amount of available disk space.
A special dump mode provides a means of moving large blocks of data, in either direction (following the manufacturer’s format) between the host computer and a vehicle network node. This option is only implemented for PWM systems.
The AVT-715 Controller runs on PC-AT machines under Windows 3.1. A 66 MHz 80486 with 8 MB of memory and at least 2 MB of disk space is required. A serial port must be available for the controller software to communicate with the AVT-715 hardware. It is recommended that at least 100 MB of disk space be available for the saving of network monitor logging files.
The AVT-715 Hardware Interface Unit
The AVT-715 Hardware Interface Unit (HIU) was designed to provide an isolated electrical interface between a host computer and a vehicle’s J1850 network. It performs the necessary protocol conversions and all required communications translations allowing a user with a PC to communicate with the subject vehicle.
SAE standard J1850 specifies a Variable Pulse Width (VPW) version with a bit rate of 10.4 kbits/sec. The standard also specifies a Pulse Width Modulation (PWM) version with a bit rate of 41.6 kbits/sec. The AVT-715 HIU was designed to communicate with both of these versions of the J1850 standard. Additionally, the HIU is capable of conducting receive operations, while in the VPW mode, at 4 times the normal speed.
The architecture of the AVT-715 HIU ensures that it is compliant with the Ford Motor Company Standard Corporate Protocol (SCP).
The HIU is a single printed circuit card with an on-board microcontroller, RAM, ROM, both VPW and PWM bus interfaces, and both RS-232 and RS-422 serial interfaces. The serial data rate is jumper selectable.
The AVT-715 is available as a complete package. Included in this version is the Controller software, the HIU in an enclosure, an OBD II compatible cable assembly (allowing direct connection of the HIU to an OBD II equipped vehicle), and a serial interface cable for connecting the HIU to a host computer. Optional equipment available include an RS-422 PCMCIA communications adapter card for a laptop type computer and other serial communications adapter cards for PCMCIA or ISA bus equipped host computers.
The AVT-715 is also available in an OEM version consisting of the HIU circuit card and a User’s Manual.
All AVT equipment is warranted for one year from date of purchase. Additionally, all customers get free software and firmware upgrades for one year from date of purchase. Telephone technical support is also available.
Specifications
Size: 4.5 x 6.5 x 0.7 in. (approx. OEM module), 5 x 7 x 1.5 in. (approx.
with enclosure).
Weight: 10 ounces (approx. OEM module).
Voltage: +12 VDC (from vehicle).
Power: 2.5 watts.
Host interface: RS-232 or RS-422 (selectable).
Host baud rate: 9.6, 19.2, 38.4, 57.6 kbaud (selectable).
Connectors: DE-9S and DA-15P.
Microcontroller: HIP 7030A0 (Harris), 68HC05 family.