Abstract
Submitted article describes an application of microcontroller PIC18F46K22 for generating DTMF (Dual Tone Multi-Frequency) signal. Used microcontroller is optimal for this application - it has timers with compare facilities, sufficient number of PWMs, powerful instruction set (extended - in comparison to classic PIC16xxx microcontrollers), etc. problematic of article relates to more branches - electronics, filters, signal generators, microcontrollers, telecommunications, programming. An important purpose was to create an experimental platform based on powerful microcontroller enabling implementation additional functions. There are together three different solutions of DTMF generating are described in article, they are compared as to the demands on external hardware and machine time of microcontroller. The first solution is based on sinus table, truncated onto 32 values. This solution uses 8-bit PORTD for value intended to external D/A converter. The second one solution exploits compare facilities of PIC18F46K22, only two pins of microcontroller are needed for described application. And the third solution is similar to the second, difference consists in exploiting of PWM microcontroller hardware. Presented solutions were created in context of works on dotation program Support of Science and Research in Moravia-Silesia Region.
Highlights
A technical task generating of DTMF signal was surely realized on many families of microcontrollers [8], in the family PIC18 it is innovative
For example if key “7” is pressed sinus 852 Hz is summed with sinus 1209 Hz, their sum is DTMF signal
For example button “7” has adequate combination 0111. These 4-bit combinations are created by a DTMF decoder, if it is connected to DTMF signal, and if DTMF signal has regular shape
Summary
A technical task generating of DTMF signal was surely realized on many families of microcontrollers [8], in the family PIC18 it is innovative. This article presents three solutions how to solve DTMF generator with the PIC18F46K22 microcontroller:. Generating two discrete signals using two 16-bit timers having compared facilities. For example if key “7” is pressed sinus 852 Hz is summed with sinus 1209 Hz, their sum is DTMF signal. For example button “7” has adequate combination 0111. These 4-bit combinations are created by a DTMF decoder, if it is connected to DTMF signal, and if DTMF signal has regular shape. Specialized DTMF generators (e.g. MV5089, Zarlink) are produced, but main motivation for mentioned three microcontroller solutions was to explore the PIC18F46K22 facilities for creating DTMF signal and its rest compute power for intended more functions
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