A basic Direct Digital Synthesizer consists of a frequency ..
DDS or is a technique that is simple to explain, but a little bit tricky to implement. It simply means that you generate an analog signal by first generating a digital signal, then use a digital to analog converter to convert the digital signal into analog. DDS has a lot of applications in various fields from communications to remote sensing. Examples include frequency sources for Sonobuoys, or as part of implementing a waveform division multiplexing (WDM) system for high speed optical communications. You can read more about these applications with . Our use for DDS is pretty simple compared to these sorts of applications, we are simply going to use it as a tone generator, and a use a potentiometer to vary the frequency of that tone. This works in a similar manner to the tone generator that we did in the last tutorial where you have a waveform that is stored as values hard coded into a table, that waveform is played by iterating through the table and writing those table values to the Arduino’s DAC. We are going to do some things differently this time, in particular, we will use timer interrupts. Lets assemble the circuit, and upload the sketch, then I’ll explain things in more detail. This sketch was based off of the project “RCArduino Quick And Dirty Synth for Arduino Due”, which you can find out more about . The amplifier circuit is the same as last time, but here is a quick run through. First hookup a to analog input 0.
All About Direct Digital Synthesis | Analog Devices
The pulse channel’s output corresponds to Timer0’s PWM output on OC0A. The pulse channel is implemented using the following direct digital synthesis scheme: During every other overflow, if the pulse channel is not silenced, a 16-bit p1_accumulator is incremented by an amount determined by the requested note frequency. p1_sequencer is obtained by right-shifting the result, and is used as an index into a pulse waveform sequence of length 8. The result is scaled to a number between 0 and 255 and then written to OCR0A, updating the PWM output corresponding to the pulse channel.
S-Meter, digital frequency display 1 kHz, direct keypad frequency entry, 96 fixed and 512 programmable memories, scanning modes, clock / timer, RDS in VHF - FM mode