This sample application is a digital frequency synthesizer that generates frequencies in the range of 0 to 20 MHz in 0.1 Hz steps. The frequency is set with a rotary encoder and displayed on an LCD. In addition there is an RS-232 serial port input which accepts commands from a PC. Accompanying PC applications implement more advanced features such as a sweep generator.

It's well documented and contains a wide variety of programming techniques including:

• Rotary encoder input, including debouncing.
• Receive half of a software UART, with a queue in case processing falls behind.
• Driving standard LCD display.
• Driving a digital frequency synthesizer chip.
• Driving a quad D/A converter.
• Use of data EEPROM memory.
• BCD arithmetic.
• Binary arithmetic with more than 4 bytes.
• Timer interrupts.

Remarkably, it all fits inside a PIC 16F84.

The files in this package:

README.HTML	- This overview file.
README.TXT	- Texte overview file.
DDS.PRJ	- Project file used by Compiler IDE.
DDS.C	- The PIC application.
SG_CMD.H	- Commands sent thru serial port. Used by DDS.C and others below.
WEIGHT.C	- Generates WEIGHT.H, depending on the clock frequency.
WEIGHT.EXE
WEIGHT.H	- Mapping from BCD display to binary codes sent to the frequency synthesizer chip.

These run on PC and send commands to PIC thru serial port:

MESSAGE.C MESSAGE.EXE	- Display message on LCD.
FREQ.C FREQ.EXE	- Set frequency.
DAC.C DAC.EXE	- Set D/A converter.
SWEEP.C SWEEP.EXE	- Sweep generator.

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Converted to HTML by Philippe Corbes (Email:philippe.corbes@laposte.net) 01/12/2002.