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FINE TUNING AN EMBEDDED IDEA

Part 1: The Land of BL2000
by Fred Eady

Start ı Z-Worldıs BL2000 ı C Meı ı Lock and Load ı Acquire the Voltage Data ı Transport and Display the Voltage Data ı Just the Beginning ı Sources and PDF

Z-WORLDıS BL2000

Nevertheless, I took Gregıs advice. So this month, Iıll take you through the land of the BL2000 sans bunny jokes or allusions to women named Alice and Grace. In fact, the Z-World BL2000 is a member of the Wildcat Series. Currently, there are four variants within the Wildcat family, which consists of the BL2000, ı2010, ı2020, and ı2030. Two of these models include Ethernet with the remaining two Wildcats, BL2020 and BL2030, opting out on my favorite feature.

Regardless of the model number, each Wildcat can provide up to 28 digital I/O channels with a maximum of seven dual-purpose unbuffered analog or digital inputs in the 28-I/O channel mix. There are 11 digital inputs that come standard across the Wildcat line. Each digital input is protected within a range of ı36 VDC. This is a good thing for me because in the wee hours of the morning I sometimes tend to let the smoke out of the I/O parts I come in contact with.

To complement the 11 digital inputs, there are 10 digital outputs per Wildcat that can sink 200 mA each at up to 40 VDC. These sinking outputs can be flipped to source at the factory if you need that capability. Iıll be describing the standard off-the-shelf BL2000, which offers four analog inputs each with 12 bits of resolution over a range of ı10.24 VDC. Like the BL2020, the BL2000 also includes two AD5320-based analog outputs with 12-bit resolution that can provide an output voltage span of 0 to 4 VDC.

The BL2010 and the ı2030 provide the most dual-purpose analog or digital inputs at seven. The BL2000 and BL2020 give you only five of the dual-purpose channels. All of the dual-purpose channels are rated for 0 to 48 VDC, with the BL2000 and BL2020 giving these channels 12 bits of resolution versus 10 bits of resolution on the BL2010 and BL2030. The input impedance of the standard analog inputs is 1 megohm. The dual-purpose inputs have an input impedance of 12 kilohms. The Z-World BL2000 analog-to-digital subsystem is based on the 14-input TLC2543. The remaining three ADC channels are used internally to monitor the reference voltages.

If youıre an embedded designer or engineer, you have to love the fact that there are three serial ports in addition to the Ethernet connectivity. The Sipex-based serial ports will do RS-232 and RS-485 in a number of handshaking configurations. That means the Z-World BL2000 is ready to network in a wired-up industrial environment as well as in the valley of the Internet. A Rabbit 2000 microprocessor clocked at 22.1 MHz provides processing power for the Wildcats. The memory complement for all of the BL20xxs is 128 KB of SRAM and 256 KB of flash memory.

Most single board computers will drive relays directly or indirectly depending on their onboard I/O circuitry. There have been many times I needed to drive only a single relay, and the downside was that I not only had to write the code but I had to design and build some additional hardware (although simple) to accomplish this. The BL2000 designers must have had the same experience, so they put a light-duty SPDT relay right on the board. Nothing is free as far as embedded resources are concerned, and the payment for the onboard relay is that it shares digital output zero.

Another annoying design task is deciding whether or not to provide visual feedback of port status via LEDs. If you fail to do this at design time, itıs a nightmare to do it in the field. Obviously, the Z-World embedded engineers came to that same conclusion because there are eight status LEDs on the Ethernet versions of the Wildcat and six LEDs (no Ethernet link or Ethernet activity LED) on the BL2020 and BL2030. Both complements of LEDs provide status for power, microprocessor health, and digital outputs zero through three.

In addition to being on time for the market, the Wildcat Series of single board computers provides a real-time clock with date that is supported by battery backup. The battery backup also extends its reach to include the SRAM. No circuitry to design, build, or buy. The battery backup is included as an integral part of each Wildcat. If you write code that could eventually chase its own tail, the BL20xx series comes standard with the watchdog supervisor subsystem.

The more I read about the BL20xx devices, the more obvious it became that these boards were designed by folks who had really worked in the field. Every Wildcat includes an onboard switching regulator that provides correct voltages to the Z-World single board computerıs electronics. That, in itself, isnıt a great feat, but the ability to take a wide range of input voltages from both DC and AC sources shows Z-Worldıs forethought. To protect the high-impedance crystal oscillator and battery backup circuits from moisture and contaminants, a Dow Corning silicone-based 1-2620 conformal coating is applied over this area of every Z-World BL20xx.

The Z-World BL20xx SBCs measure 3.43ı ı 4.15ı ı 0.82ı. An optional Z-World BL20xx enclosure fattens up the footprint to 4.9ı ı 5.6ı ı 1.1ı. Again, applying the embedded rule that nothing comes for free, if there are LEDs on the Wildcat, the case will have to accommodate them. The Z-World guys and gals were way ahead of us and supplied light pipes for their enclosure.

Where did I get an official enclosure? Easy, the Z-World BL2000 Tool Kit. No aspiring BL2000 programmer should be without this handy dandy collection of wires and gadgets. The BL2000 Tool Kit includes:

• The Unibox enclosure complete with mounting screws and LED light pipes.
• Rabbit 2000 processor easy reference poster
• Z-World engineering demo board
• 22-AWG wire package for connecting the demo board to the BL2000
• Rabbit programming cable
• Z-World screwdriver
• 9-VDC power brick
• BL2000 userıs manual

The demo board comes equipped with a buzzer, four more LEDs, four momentary contact mini switches, and a screw terminal interface. The Unibox enclosure is actually a top cover and a matching wall or panel-mountable base plate. The base plate is a perfect SBC holder for doing initial development with the Z-World BL2000. Iıve given you a visual of the Z-World BL2000 SBC in the mountable portion of the Unibox in Photo 1.

Photo 1ıUsing the Unibox bottom makes it difficult to damage the electronics on the back side of the Z-World BL2000.

In a series called "Rabbit Season" (Circuit Cellar 122ı126), I fully describe the inner workings of the Rabbit 2000 processor. So, I wonıt go there this time. Instead, Iım going to concentrate on getting a brand-new version of Z-Worldıs Dynamic C loaded on a brand spankinı new 900-MHz AMD Thunderbird Iıve set up in the Florida room just for that purpose.

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