ADC in VHDL and De0 Nano ADC VHDL Code

You can download free (time limited) Verilog to VHDL (and vice versa) converters.

Look at X-HDL from X-Tek Corp:

http://x-tekcorp.com/livesite/pages/x-hdl (http://x-tekcorp.com/livesite/pages/x-hdl)

I'd hope the DE0-nano comes with some sample code that implements the physical layer interface to it's own ADC. Assuming that's written in Verilog you should be able to pass that through X-HDL to give you a something to work with.

If not, the interface is a very simple SPI interface detailed in the following document:

ftp://ftp.altera.com/up/pub/altera_material/12.1/tutorials/de0-nano/using_de0-nano_adc.pdf (ftp://ftp.altera.com/up/pub/altera_material/12.1/tutorials/de0-nano/using_de0-nano_adc.pdf)

A little lateral thought should allow you to successfully write your own interface to it