AD9833 DDS Generator Board

A frequency generator board based on the AD9833 chip. Purchased as a frequency-tunable clock signal source. The board is equipped with a 25 MHz oscillator. It can generate signals from 0 to 12.5 MHz (though waveform quality may not be satisfactory across the entire range). The waveform can be switched between sine, sawtooth, and square wave. All necessary signals are brought out to pin headers. Controlled via SPI interface. Architecturally, it contains one 28-bit phase accumulator register, two frequency tuning registers, and two phase offset registers. Only one pair (frequency/phase) can be active at a time. This allows for frequency modulation without phase discontinuity or phase modulation, if needed. However, there is no dedicated hardware input for selecting the register pair – switching is possible only via SPI commands. Oscilloscope waveforms follow below. Test setup To control the DDS, commands must be sent via SPI. I am using an STM8 (STM8S105K4T6) with its hardware SPI. It wa