Seems you'd like to outsource the whole system engineering and purchase
department part... ;-)
Some thoughts to start with:
To have a starting point, you should sketch what functionality needs to
go into the FPGA, i.e. do a detailed block diagram of datapath, buffer
memories, controllers (possibly IP), interface (possibly IP). For IP's
you usually get information about complexity and you can sum up the IP
complexity with all the memories and arithmetic compleity you require.
Now select an FPGA that suits well your defined needs (reading at least
the "executive summary" of some of the most familiar FPGA can't be
avoided), and make sure that the familiy has bigger and smaller FPGAs in
teh familiy with identical footprint (for later exchange without need
for redo the PCB).
With this rough selection, purchase a development kit of the required
family to implement your first HW version on. Working with the
development kit helps you:
- Find out wether the FPGA choice was fine and the design fits well >
You may adapt to smaller or bigger one for your own PCB
- See what "minimal surrounding HW" you require and have a starting
This should give a pretti well starting point for your FPGA.
However, one question remains: If you are price sensitive, you should
check whether there is any cheap mass-product off-the-shelf
microprocessor (available with many kind if possible I/F and other