Nuts & Volts - January 2006

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FIGURE 4. Hardware Schematic.

31 COMMANDS! WHAT CAN I DO WITH THAT?

PIC projects. You can later upgrade to various professional programmers that will work on a laptop or USB port.

SO WHAT DOES ALL THIS COST?

This is where you might be shocked. A 16F876A Microchip PIC will cost around $10. The PicBasic Pro compiler shown in Figure 2 comes in a limited sample version that can be downloaded for free from www. melabs.com It is limited to 31 command lines, but that is more than enough to get started. It is also limited to certain Microchip PICs: 16F627(A), 16F628(A), 16F84(A), 16F870, 16F871, 16F872, 16F873(A), 16F874(A), 16F876(A), and 16F877(A)

are all supported. This gives you plenty of PICs to work with.

The serial port PIC programmer shown in Figure 3 can be obtained from my website for $24.95. The kit form will be cheaper and hopefully available by the time you read this at elproducts.com

I also recommend the Microcode Studio IDE software from www.mecanique.co.uk/code-studio It’s also a free download and was designed to work with the PicBasic Pro compiler. It makes writing PicBasic code so much easier. You also will need a few minor components to make the PIC run, such as the clock resonator mentioned earlier and you will need some type of 5V power source along with a few resistors. This can all be built on a standard breadboard.

Since I stated all this could be done for less than $50 and we’ve designated $10 for the PIC and $25 for the programmer, you have $15 for the breadboard, wiring, and other components. Not bad right?

You may be wondering, what good is all this if you only get 31 commands to work with? The PicBasic Pro compiler is so efficient to write code with, you really can do many simple home projects with a single PIC chip and less than 31 lines of code.

For example, I’ll build a simple LCD controller out of a 16F876A PIC chip. It will simply display the message “Hello World” but can be expanded in the future and still use the sample version of the PicBasic Pro compiler because I’ll do this with far less than 31 commands.

To do this, first download all the free software and install the Microcode Studio software and link it to the PicBasic Pro compiler. You’ll have to follow the MCStudio instructions, but in most cases, it will find the PicBasic Pro compiler automatically when you install it. After these steps, you are ready to program your first PIC.

The project schematic is shown in Figure 4. All the connections are straightforward. The PIC 16F876A has a 4 MHz resonator connected to the OSC1 and OSC2 pins. Two 20 pF capacitors are connected to the OSC1 and OSC2 pins to ground. You can get a 4 MHz resonator with the capacitors built in from companies like Digi-Key. The PIC also needs a 1K resistor connected from 5V to the MCLR pin. The MCLR pin is the reset pin so you want this tied high. Pulling this low will reset the PIC, so adding a momentary push button from MCLR to ground is an optional.

The LCD is a parallel version with a Hitachi 44870 driver chip inside. This is a common LCD available all over the place for under $15 and usually less than $10. Connect the LCD per the schematic including the 1K pull-up resistors to 5V. These help guarantee a proper voltage level between the PIC and the LCD. After this, the project is ready to be programmed. The hardware is shown assembled in Figure 7.