The ESP-2 MI 2-port serial hub by Equinox does its job--enabling serial peripherals to function as IP-enabled devices on the network--efficiently and without any fuss. You simply plug a serial device into the hub, connect the hub to the network and configure the host computer with the software. If you were able to use your device when it was directly attached to the computer's serial device, then you can be using it on the network within ten minutes of unpacking the ESP-2 hub.

The ESP-2 is a small (1.75" high x 4.75" deep x 6" wide), light (less than a pound) device with 32MB of SDRAM memory, 4MB of Flash memory, an auto-detecting 10/100Base-T network interface with a RJ45 connector and two 9-pin serial ports that support RS-232, RS-422 and RS-485. The configuration and management software can run on Linux (I used Red Hat 7.3), AIX, SCO OpenServer/UnixWare and Microsoft Windows 2000/NT/XP. The key point of the device is the unit converts data between its serial ports and its network interface and then communicates across the network. The hub packetizes the data and sends it to its host computer using TCP. Serial devices such as a barcode scanner can be out in a warehouse, where the scanner needs to be, sending data to a server that is protected in a restricted area, where the server should be. Previously, each device would need to be attached to a computer within a few feet of it, which limited the mobility of the equipment and greatly increased the number of computers required.

The intended audiences for this device are the retail point of sale, hospitality, medical and industrial communities. Many industries have their own unique equipment to monitor production. This equipment gets hooked to a computer that then packages the data and sends it where it needs to be. This design is fine, but it leads to large numbers of computers that otherwise would be unnecessary. Enter the ESP-2; it takes those serial connections, eliminates the computer in the middle, packages the data and again gets it on the network. The computers are eliminated, saving money to purchase, maintain and power the computers. In addition, large amounts of space are saved while also making the scanner/printer/other equipment much more mobile, possibly eliminating many redundant stationary pieces of equipment. The ESP-2 excels in these areas.

While these areas are the main focus of the device and extremely useful, I used the hub in several different ways. One of my computers ran out of interrupts so the various cards on the motherboard could function, and I freed up IRQs 3 and 4 from the serial ports by reconfiguring the BIOS. I used the hub to allow me to use serial devices with this computer again. My PalmPilot worked immediately when attached this way. Another use is as a crude security system. Attach an old digital camera to the hub and could control it by snapping pictures with The GIMP--crude but potentially useful.

Some of the supported operating systems can be installed directly from the CD-ROM. As clearly outlined in the instruction guide, Linux sysadmins must build floppies from the CD-ROM and then install from the floppy. The instructions walk you through step by step and get the software installed with no real thinking required on your part. The key part of the installation is making two devices under /dev, /dev/ttyQ01e0 and 1. Once these are made, you use them as you would /dev/cdrom or /dev/ttyS0. For my PalmPilot, for example, I made a symbolic link between /dev/pilot and /dev/ttyQ01e0, launched kpilot, hit sync on the cradle and immediately heard the happy beep.

Equinox did a great job with the instructions and the installation software. Literally within minutes of opening the box, I had it plugged in and found on the network. From there, it took only a couple minutes to get a device working through the hub.

The device supports RS-232 out of the box. If you need to use RS-422 or RS-485, you have to open up the hub and reconfigure some jumpers, as detailed in the instructions. As a word of warning, while this device can be used across subnets, it does no encryption, so all data is sent clear-text. It is intended to be used within a factory where security is probably as big a concern. You could put a hub and some equipment together and have it working with a computer on the other side of the world, but your potentially sensitive data would be visible to everyone. Equinox does have higher-end products with security.

The devices, /dev/ttyQ01e0 and 1, made during installation, bring up two points about the capabilities of the hub. A host can control multiple serial hubs and therefore get data from more than two instruments. This is set during the discovery and configuration script at /usr/bin/espcfg.

Second, the hub does support bootp and DHCP but only for infinite leases. Once it has an address, it keeps it until the unit is reinitialized from the front panel. A hub configured as number 5 would work with /dev/ttyQ05e0 and 1. Up to 64 ESPs can be controlled at a time. The literature also says that multiple hosts can work with one hub, but I did not try this. The configuration script allows you to turn off port 2 on the hub if you are not going to use it.

A nice capability of the software is the replace option. If a hub stops responding for whatever reason, you can replace it with another one and keep the same connections. Figure 1 shows a representative screen of the espcfg program.

Figure 1. A Representative Screen of the espcfg Program

The other extremely useful program is espdiag, especially the data scope. This allows you to watch the data going through the hub. Figure 2 shows the diagnostic program and data scope. The equipment uses TCP/IP, port 4000 on the hub and a randomly assigned port on the host computer, which was always in the range of 32000 to 34000 in my testing. Ports 161 (SNMP) and 69 (tftp) also are used occasionally by the hub. 161 is used by the configuration program, and 69 is used by the data scope program.

Figure 2. The Diagnostic Program and Data Scope

,P> The ESP-2 is designed to be used in a variety of ways. It can sit on a table, be mounted on a wall or use DIN rails with the optional mounting kit ($30). Power can from its own AC power transformer or a latching connector.

The ESP-2 MI serial hub does what it says it will do, quietly and efficiently. If you manage a store, factory, hospital or similar facility, the ESP-2 could make your operations more efficient and save you some equipment costs.

Red Hat 6.2 - 8.0, Mandrake 8.2, Turbolinux 7.0 Server, Suse 7.2 and 8.0, Slackware 8.0, Debian 2.2r4, Caldera 3.1.1. See the Equinox web site for more details.

U.S. List price: $349.00

Brian Gollsneider is working on a PhD in Electrical Engineering from the University of Maryland. When not buried in research, he is a UNIX instructor for Learning Tree International.