SRAM DDS

While poking around some PCB boards for components I found a SRAM(LH5116) chip with 16K and a supply of 5V, in the same instant I thought:

It would would be fun add a DAC at the SRAM output...

There are already some DDS (Jesper’s DDS) made for the atmega that manage to generate 200kHz~300kHz sinewaves, but, maybe with an external RAM I could achieve better performance ?

The 250kHz "wobbly" sinewave, the FFT is clean enough

Data flow schematic (8 bit for address used of the 11 available)

The basic idea was to load the waveform to the SRAM to save some operations in the uC, since the atmega isn't a very fast processor and the load takes 3 cycles. Currently I did managed to generate a 250kHz sinewave with some resolution. The biggest issue is the lack of a Sample & Hold, which makes the output sensible to RAM logic propagation times and sometimes produces glitches.

I may continue to poke around this, but, hopefully I will received a new DDS generator soon. Nevertheless it was a fun idea to try out.