Another pattern generator

[ppppenguin]

if you do decide to use a homebrew R-2R ladder then you're in good company. The Aurora SCRF converters use the same method. There's a clever twist in the resistor values and digital logic to get 10 bit resolution from the 7 bits that come out of the FPGA. I won't explain further as it might be giving away Darry's trade secrets. Let's just say that if you have a fast enough clock and suitable oversampling you only need 1 bit to make an excellent DAC. That's how most audio DACs work but the clock rate would be stupidly high for video. A very simple pulse width control with 1 bit out plus a large enough R/C filter makes a good control DAC. I use this method to do the vernier frequency adjust on TCXOs.