Automotive Test Systems


A leading designer and manufacturer of vehicle test systems typically uses a host PC connected to a custom test adapter that interfaces the equipment under test. A typical system tests controllers used in engines and transmissions. These controllers provide a variety of interfaces and protocols for communication including Can bus, J1708, and RS-232 that allow access to important information regarding the operation of the unit during the test. The leading designer and manufacturer’s custom adapter for each controller acts as a protocol converter to send the data back to the host PC via RS-232. Since the data rates vary by device and can be quite fast, a high-speed multi-port RS-232 card was required for the host PC. Like many current PC’s, their platform offered only PCI Express slots for expansion.

Application Requirements

Each test system is customized using their proprietary adapter modules to fit specific customer requirements. Uses vary from testing electronics prior to vehicle installation to testing equipment installed in a vehicle or returned for repair. A RS-232 signal from the test system sends back pertinent information to the industrial computer for analysis. A typical test system uses eight adapter modules, so a PCIe board with 8 or more RS-232 ports was required.

The Sealevel Solution

The vehicle test system designer and manufacturer chose the Sealevel 7161e 16-port RS-232 PCI Express card over several competitors after concluding that the 7161e offered the “right solution at a better price”. They have used Sealevel serial products in the past and the 7161e was able to virtually “drop-in” to the system with little implementation required other than loading the board’s software driver. The board and utilizes 16C854 UARTs to provide 128-byte Tx/Rx FIFOs for maximum reliability in data-intensive applications and supports data rates to 460.8Kbps. The boards ship standard with a fan-out cable that direct connection to DB-9 or DB-25 connectors.

PCI Express cards communicate with the host processor using two pairs (one transmit, one receive) of low voltage serial signal connections called “lanes”. The connection from the host processor to a PCIe peripheral, the “link”, can consist of a single lane (X1) or up to 32 lanes (X32). The PCI Express specification was designed with compatibility in mind, so each of the following scenarios is supported:

A PCIe expansion card will work in any slot with at least as many lanes as it contains; X1 cards will work in any PCI Express slots.

An expansion card with a larger number of lanes will work in an expansion slot with a smaller number of lanes provided it fits mechanically. In this case, the expansion card will throttle back to the number of lanes supported by the expansion slot, so the performance will decrease. Adapters are available to help accommodate this configuration.