Nuts & Volts - January 2005

Project

Figure 6. The Digital Filter Development Board is teamed up with a Little Bits to complete the realization of a PIC10F206 bit-bang serial port.

Communicating With Little Bits

There are no USARTs (Universal Synchronous Asynchronous Receiver Transmitters) or UARTs (Universal Asynchronous Receiver Transmitters) contained within the PIC10F206 silicon. So, there’s no native PIC10F206 serial

communications functionality. Just because the specialized UART hardware doesn’t exist doesn’t mean we can’t implement a software PIC10F206 UART of our own.

In fact, we can do just that and — thanks to the HI-TECH PICC C compiler — we won’t have to write any of the serial communications drivers from scratch. All of the bit-bang serial driver code that comes with HI-TECH PICC C compiler is shown in Listing 5. You can study the code in detail if you wish. However, the only things you have to know about the serial driver are the serial functions that you will use when applying the driver code. To send a character, use the putch function. To receive a character, use the getch function. A optional function called getch echoes the incoming character.

This is where the 20-pin female connector I added to my Little Bits comes into play. As you can see in Figure 6, I’ve called upon a Digital Filter Development Board to aid the Little Bits in getting its serial port operational. I’ve wired the Digital Filter Development Board’s SP233ECT RS-232 IC into one of the PIC10F206 microcontrollers on Little Bits via a 20-pin male header on the Digital Filter Development Board. Only four connections are necessary, with power and ground being givens. Look again at the beginning of the code in Listing 5. You’ll see that I’ve designated GP2 as the transmit pin and GP3 as the receive pin and specified a baud rate of 9600 bps. I’ve detailed the PIC10F206-to-Digital Filter

E l e c t r o n i c s NUTS & VOLTS

F o r

E v e r y t h i n g

Interface a sharp LCD display to your BASIC Stamp® or other micro-controller project with ease. No-solder wiring harnesses and easy mounting kits available too. See www.seetron.com today.