FPGA - DIY Programming

Question

I've been programming microcontrollers for a few years now, and I've just discovered FPGA's after taking a digital design class. After doing some research into different FPGA's, development boards, etc, I'm still hesitant to buy any because I wouldn't know how to make my own version of the final "product." I've put PIC's, SAM's, AVR's, etc. on to custom PCB's with no issue, so I'm not worried about that--my main concern is programming an FPGA without a manufacturer's board.

My specific question: Would an FPGA function if I took the bitmap file generated by Quartus, Vivado, iCEcube, etc, wrote it to an SPI flash memory chip beginning at address 0 (say, via an FT2232H), and connected the flash memory to the SPI pins of an FPGA (with the MODE config set properly)?

I apologize for the partial hypothetical; I'm fairly sure that's all Lattice's Diamond Programmer does, but I wondered if that approach would work for FPGA's from different manufacturers, or whether say, Quartus added additional "window dressing" or headers to the memory while writing it.

Let me know if there's anything I can do to improve/clarify the question, or if I'm missing a big point in the FPGA programming process. Thanks!

Answer 1

Yes, it would work just fine.

Actually, the development tools for most FPGAs allow you to program the external flash directly through the FPGA's own JTAG connection, eliminating the need for a separate programming interface for the flash.

Answer 2

When you say "the [sic] bitmap [sic] file generated by ", the answer is Yes as long as you pick the right one -- you made a slight error by using the definite article since there isn't just one file generated.

For example, Quartus can produce SOF, POF, and JIC files. The last one is what you use for indirect programming via the FPGA JTAG. It would not be useful to write that to the SPI flash. The SOF is for loading over JTAG to run your design in the FPGA transiently. POF is what you need to load into the flash chip.

See FPGA: Bitstream vs. SRAM Object File for a lot of useful information on what the different files mean from each of the different vendors.

Answer 3

Would an FPGA function if I ... connected the flash memory to the SPI pins of an FPGA (with the MODE config set properly)?

If I understand your question correctly, you want to write the FPGA configuration (e.g. your compiled HDL model) to an SPI EEPROM or SPI Flash and you want the FPGA to program itself using the data on the SPI IC.

(If I understand Dave Tweed's answer correctly, he understood your question in a different way.)

At least many SPI Flash memory devices would NOT work because SPI Flash memory ICs require a certain waveform (e.g. the address to be read) to be sent so the data is read out from the IC.

This waveform is not the same for all Flash memory devices. Even when only looking at SD memory cards (which can also be used as SPI Flash memory) we find two variants requiring a different waveform to be sent to the card before the card reads out the data.

When setting the mode pins of the FPGA correctly, the FPGA will send some waveform that instructs some serial memory device to send the data. However, because different ICs require different waveforms, the waveform will not be understood by all Flash ICs but only by certain types.

I know that Altera produces special Flash or EEPROM ICs which a are compatible to their FPGAs.

Answer 4

If you want to write an FPGA bitstream to the flash without the official FPGA programming tools, you'll most likely want to convert that bitstream file to an open binary format that you can easily read, like raw binary, Intel HEX or Motorola SREC (example). This will strip any proprietary headers that an FPGA bitstream may contain.

This way you will be able to program the flash using the tools from the flash manufacturer (or your own tools), or even order the flash chips pre-programmed with your FPGA bitstream.