FPGA or Microcontroller for Production Design?

Question

I have a very simple LED driver circuit connected to a 7 segment display and a couple of buttons. I want to move this design to production, on a scale of +1k units.

I have implemented the design on an FPGA partly because it seemed simpler to hook everything together and because the development board I have already has buttons + a 7 seg display. I'm also under the impression that the synthesized design is more easily "transferred" to a PCB. However, I can't figure out a clear answer.

The design is simple enough that I could make it for an MCU pretty easily. AFAIK, with an MCU, you get all your components and the MCU and solder them onto a PCB (for a prototype), and once the design is final, you could get this PCB assembled by other companies. I don't know what the process would be for the FPGA implementation. so I was wondering what advantages/disadvantages there are with going with an MCU or an FPGA based design?

EDIT: I'm trying to figure out the workflow. I'm using Xilinx ISE and I have synthesized vhdl. How do I convert that to a schematic I could get printed? And does this direction offer any advantage to using an MCU based design

Answer 1

If you are about equally at home with an FPGA or a microcontroller for development purposes, a microcontroller will cost less in small quantities.

The lowest cost FPGA listed at DIGIKEY in 1,000 quantity is $US2.85/1000.
Digikey have a microcontroller part which would do this task for about $US0.30. This is an "outlier" and you would usually expect to pay $US0.50 - $1.00 in 1000 quantity. For $US0.68/1000 you get this ST offering - STM8S103xx with UART, SPI, IIC, 5 x 10 bit ADC, multiple timers and 28 I/O lines.

When it comes to doing "bits and pieces" around your core design a microcontroller is going to be substantially more flexible and take less time, unless you are an FPGA guru.

Assembly wise both FPGA and microcontroller are similar. In most cases you will need external driver ICs or discrete components to drive higher current loads - which probably includes your 7 segment display if it is LED (and not if it is LCD).

Answer 2

First you need to figure out what the final schematic and BOM (bill of materials) of your FPGA-based design is. Then price out the parts at 1,000 unit quantity.

Next, design the MCU system, and price out its BOM. Now price that BOM out at 1,000 unit quantity.

Finally, look at the PCB size for both designs. A smaller PCB will be cheaper than a larger PCB, unless the smaller PCB requires more layers.