communications

SAE J1939 is the standard communications network for sharing control and diagnostic information between electronic control units (ECUs) which reside on heavy duty and commercial vehicles. Examples of such vehicles are school busses, cement mixers, military vehicles, and semi-tractors.

Controller Area Network (CAN) is the most widely-used automotive bus architecture. Here are some reasons why.

At peak, some automobiles contained up to three miles of cabling. To reduce the cost and weight of wiring and still allow ECUs to become more intelligent, new methods had to be found to reduce the amount of wiring. The CAN bus has since found application in other industries as well.

Distributed systems require protocols for communication between microcontrollers. Controller Area Networks (CAN) and Serial Peripheral Interfaces (SPI) are two of the most common such protocols.

Network processors are programmable chips like general purpose microprocessors, but are optimized for the packet processing required in network devices. But what are they good for and how do they work?

The Internet Protocol (IP) is the glue that holds an internet together. Here's a compact implementation of the IP layer for embedded C programmers.

The address resolution protocol provides a necessary bridge between physical and logical addresses on a TCP/IP network.

Every system on a TCP/IP network has two addresses, one physical and one logical. The address resolution protocol (ARP) provides a necessary bridge between these two addresses.

Merely adding a protocol stack and networking API to your software doesn't make you TCP/IP ready. You'll also need to assign your product a MAC address.

Any book on TCP/IP will tell you that each network-connected device has a globally unique hardware address. But where, exactly, do these addresses come from? And why is it that the authors of books on TCP/IP never bother to answer this or any other practical implementation question?

If your embedded system is on a network, the key question is not will you include TCP/IP but which subset of the Internet Protocol suite will be supported in your product.

CRCs are among the best checksums available to detect and/or correct errors in communications transmissions. This article shows how to implement an efficient CRC in C or C++.

Many common types of data transmission errors cannot be detected by additive checksums. This article describes a stronger type of checksum known as a CRC.

As engineers design more and more products with embedded computer systems that require connections of one sort or another, short-range wireless protocols offer an attractive alternative to wired connections.

Quite a few embedded systems include multiple processors. Sometimes these processors stand in isolation, but more often they're required to communicate over a multidrop bus such as EIA RS-485 or RS-422.