PCB with Mixed Analog and digital
Well I do not see any diagram but from what I have learned:

only provide a single path for a current, so do not connect different grounds at different places
with analog and digital grounds connect em at a single point beneath the AD or DA Converter
depending on the design just short circuit the grounds at this point or use one or more capacitors to block dc but allow ac
for different voltages use a single ground plane and distribute buffer capacitors (normaly groups of 3 parts in parallel like 100n,10n,1n to improve frequency response) over your design (there are some comercial calculation programms where to place them, but when you place 5-6 groups to cover the overall area and then place some more near major sources and sinks... that should be sufficient in many cases) --&gt; if your design needs more precise calculations you need to dig in literature and courses, then you really need to invest time and money

PS: seperating the digital and analog ground is a measure to reduce noise and such influence to the adc precision. You need this if you messure very low signal differences and it commes into play when doing fast conversion rates with fast signals. if you just want to distinguish 1V dc or 2V dc,... its maybe overengineered.