Servo - August 2008

FIGURE 10. Programmer Parameters Window.

power and ground connections to operate. To create the demonstration unit for the high school, we used one of our breadboards from Beginner Electronics.com. The breadboard circuitry included the power connections and the connections to the 2x40 LCD per the schematic shown in Figure 11. We had a large box of brand new surplus 2x40 LCD’s available, so we did the demo with

that LCD. (The same software will work with any two line LCD.)

The software is shown in Listing 1. The first section that has all the DEFINEs is required for the way we wired up the LCD. This shows how the PICBASIC Pro compiler handles the setup in the background to make the code easier to write. The final example took 23 command lines, but if we used a different PIC and used the default DEFINE settings, then we could remove the DEFINEs and the program reduces down to 13 lines. We are also writing to the LCD several times within those 13 lines so this is more efficient than other BS1 examples I saw.

The unique section of the code required to use the PIC16F690 are the special register setups shown below. The sample programs may need these same lines of code. These settings make the pins digital instead of the default analog mode. They also shut off the internal comparator that is on this part.

‘ Set A/D ports 0-7 as digital
ANSEL = 0
‘ Set A/D ports 8-10 as digital
ANSELH = 0
CM1CON0 = 0
CM2CON0 = 0

‘ Comparator 1 off
‘ Comparator 2 off

The rest of the program is fairly simple to understand so I won’t go through it all. The point is the code was short and simple enough to fit within the 31 command limit with more space for a few more functions.