A major concern of computer manufacturers ought to be the compatibility of new hardware and software with legacy equipment. Unfortunately, this doesn''t seem to be the case. The current trend of building closed-box computer systems, with a limited number of communication ports and expansion slots, makes things difficult for industrial and commercial system developers, and for the users of these systems.
Often, industrial users need to upgrade automation systems and are faced with two choices: either buy a completely new system in which all the pieces have compatible interfaces, or replace specific pieces and grapple with interface problems. Since many of these users have millions of dollars in legacy equipment with serial interfaces, and it still works well at speeds adequate for their applications, replacing individual pieces is strongly preferred. When industrial computers with closed-box architectures control the new equipment, serial interface solutions are needed.
More often than not, legacy devices are designed around RS-232/422/485 protocols. In fact, many users and system integrators still prefer these protocols for new systems, because they provide robust communications, ease of use, and the lowest installed cost. Depending on your perspective (few statistics are available), the use of these protocols remains relatively constant or is slowing or declining. A case can be made that this trend will continue over the next few years. (See Figure 1.)
This situation has spawned a serial communications interface market with annual sales that exceed $500 million -- much larger than many would imagine. The market includes expansion boards for legacy ISA and PCI systems, and adapter boards for computers equipped primarily for newer protocols, such as PCMCIA, USB, and Ethernet. Many of these serial communication adapters and interfaces have robust designs, rugged DB-9 connectors, and built-in surge suppression that make them the logical choice for industrial applications. Moreover, they overcome distance limitation associated with USB and some of the other protocols. Innovative hardware drivers and embedded application software make these products easy to use.
Ethernet is becoming the most popular networking interface while most legacy devices remain serial-based. Serial device servers are the most common method of incorporating legacy equipment into an Ethernet environment. Still, configuring network servers and devices can be very complicated, especially in a plant environment where the installer probably is not an IT systems expert. To help solve some of these connectivity problems, makers of Ethernet adapters are beginning to supply software that simplifies installation processes, such as assigning TCP/IP addresses and setting up network servers.
Interest in wireless networks also continues to grow, as it holds the potential for leaner, more flexible manufacturing systems. However, in applications such as wireless warehousing operations, industrial users have legacy equipment problems similar to those mentioned earlier. For those contemplating new systems, there is uncertainty as to which wireless protocol will be the best long-term investment. Both Bluetooth and IEEE 802.11 are strong contenders, but few wireless devices or systems built around these standards are available for industrial use. Third-party adapters and interface boards are already filling the wireless-RS gap for existing DSSS and other RF systems. As systems designed around new wireless standards come on the market, interface manufacturers will no doubt fill the need for adaptors that serve surprisingly resilient serial device applications.