Hella North America is working with General Motors and other electronics suppliers to develop new automotive sensor technology.

The electricals supplier is part of a group, initiated by GM and including Bosch and Hitachi Limited, to define a digital transmission scheme between sensors and controllers. The new interface is a one-way communications procedure from sensor to controller, which does not require a coordination signal from the controller.

The new protocol is intended as a replacement for the lower-resolution, 10-bit analogue-to-digital methods and pulse width modulation. It also provides a simpler, low-cost alternative to control area network or local interconnect network. In addition, the new protocol also will save costs in controller-hardware systems by using one line for several signals.

The first application of the new data-transmission protocol is targeted for air flow meters or non-contact position sensors. Hella claims to be a market leader for accelerator pedals and a supplier of inductive non-contact sensors used in applications such as throttle bodies, steering sensors and level sensors for headlamp level-control and suspension-control systems.

The demand for more robust and reliable electronically controlled systems will lead to increased use of non-contact position sensors in a number of other applications. As a result, sensor, controller and vehicle manufacturers are investigating ways to take full advantage of this electronic-sensor technology by implementing appropriate interfaces.

A spokesman said the change is necessary because the existing analogue transmission protocol is sensitive to changes in connector resistance and other disturbances and also cannot meet the demands to reliably and more rapidly transmit data with more than 10 bits of resolution.

Under the protocol, data is transmitted as pulse-length variations. It is designed to transmit two 12-bit sensor data plus checksum (to ensure data accuracy), as well as safety and status information. Data are transmitted in a sequence, which consists of a calibration pulse followed by 8 nibbles of 4-bit information. This data can be transmitted in less than 1 millisecond and is applicable for redundant high-speed sensors, for example, throttle, pedal and other sensors within the drivetrain system. Microcontroller manufacturers have confirmed that future controller hardware can handle such a protocol.

The protocol is intended to be free and open for all users. A free protocol allows a common approach throughout the industry, which can lead to less-expensive sensors and controllers. The protocol also can be used for sensors in other vehicle systems. The group plans to release the specification to automotive standardisation organisations such as the Society of Automotive Engineers.