Nuts & Volts - July 2005

The Ultimate Utility Meter — Part 1

In Part 2, we will delve into the software, and I will lay out a complete set of operation instructions, as well as a few real-world examples.

Okay, we have a lot to do, so let’s get started. I will provide a parts list at the end of the article with a complete listing of all the components I used to build the UUM.

Construction

Figure 3. The Dios microcontrollers are the heart of the UUM.

Figure 4. One of the microcontrollers controls this Crystalfontz graphic LCD.

Two Dios microcontrollers are at the heart of the UUM (see Figure 3). These microcontrollers are connected via a hardware universal asynchronous receiver/transmitter (UART) in each chip, running at 115,200 baud. You don’t need a programmer for these chips; just download the free compiler from the Kronos Robotics website (www. kronosrobotics.com).

The first Dios is a 40-pin microcontroller that controls the Crystalfontz CFAG12864B-YYH-V graphic LCD shown in Figure 4. This LCD has a 128 x 64 resolution and its own negative voltage generator, so interfacing is very straightforward. This Dios is also connected to a hex keypad. This assembly makes up the serial graphic LCD module.

the Dios Utility Carrier. This carrier comes with lots of extra headers that can be used for different applications. It even comes with its own mounting hardware.

I chose to use the Dios for this project for various reasons, but the most important reason is the raw power of the Dios. The Dios can run 130,000 to 200,000 high-level commands per second in the Basic language, and with inline assembly, it can run 10,000,000 instructions per second.

Schematic 1. The schematic for a more personalized carrier board.

Note: You may also use the Crystalfontz CFAG12864B-TMI-V

To simplify construction, I used a special carrier called a Dios Universal LCD Carrier. This carrier board is sold as a kit from Kronos Robotics and features a built-in regulator and PC interface, as well as a header for the Crystalfontz graphic LCD. You don’t have to use the carrier, but it will make hookup and assembly easier.

The second Dios is used as the logic analyzer and signal generator. It sends commands to the serial graphic LCD to display all data, and it receives data from the serial graphics LCD when a key is hit on the keypad. This assembly makes up the utility controller module.