I would like to generate an arbitrary waveform, say a square wave or sine wave, using the AD 5781 DAC. How can I program the DAC in order to do this? I'm not sure where to start...
You need a power supply, the complete DAC circuit, memory that contains the digital data for the expected waveform and a device that transfers the memory data to the DAC.
This device can be PC, an FPGA, a microcontroller, a CPLD....
These devices need some code to operate.
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Btw. It is impossible to reproduce waveforms like square wave, because they contain infinite high frequency components.