Philips LPC9xx DTMF Tone Generator

This example runs on the Philips LPC935 and shows:

• A Timer Interrupt Service Routine (ISR) in C,
• How to generate Time Delays using the Timer ISR,
• and How to generate DTMF output on DAC1.

This Example may be debugged using only the uVision Simulator and your PC--no additional hardware or evaluation boards are required. The Simulator provides cycle-accurate simulation of all on-chip peripherals of the LPC900 device family.

The Logic Analyzer built into the simulator may be used to monitor and display any variable or peripheral I/O register. It is already configured for this example to show the timing of the DTMF output.

The Performance Analyzer (which is also built into the simulator) graphically displays the time spent in each function. You may use this tool to determine which functions require the most CPU time and which functions must be optimized for performance.

For users with EPM900 or MCB900 hardware, you may download the application into Flash ROM. Refer to http://www.keil.com/mcb900 for more information.

Technical background about the algorithm used is documented in Application Note 178: Programming and Debugging of Analog Signal Processing Algorithms.