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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!

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  • \$\begingroup\$ By "bitmap" you mean bit-stream? \$\endgroup\$ – Eugene Sh. Apr 10 at 18:02
  • \$\begingroup\$ This question has be asked in a different incarnation before \$\endgroup\$ – laptop2d Apr 10 at 18:02
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    \$\begingroup\$ On your first FPGA board design, I'd suggest to provide 2 methods of device programming (plus the vendor's JTAG header). Place jumper locations to allow you to change the MODE pins as needed. It's very easy to mess these up and it's good to have back-up plans. Also be sure to provide testpoints for INIT and DONE (or whatever Lattice uses to indicate the programming state). \$\endgroup\$ – The Photon Apr 10 at 18:26
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    \$\begingroup\$ The process control required to mount BGAs, especially high pin count ones is tighter than something like a QFP. The fact there are more balls means there is a higher probability of bridging or bad connections and since they are hidden you won't be able to detect problems (unless you have an X-ray) prior to running the thing to see if you have any issues. And if you remount the component then you have to reball it which requires more equipement. FPGAs are also expensive chips that you don't want to damage. Large BGAs are where things like PCB preheaters become necessary. \$\endgroup\$ – Toor Apr 10 at 20:01
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    \$\begingroup\$ I used to work at a place where the techs did nothing but rework all day and they had hot air stations (tighter temperature control and more reliable than the heat gun) and they were unable to reliably hand solder BGAs. I don't think they had a preheater so if you are going to try it, get a preheater and use a cheap chip (maybe even daisy chain dummy BGA package so you can verify your connections electrically until you've nailed it before doing the real thing). \$\endgroup\$ – Toor Apr 10 at 20:08
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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.

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    \$\begingroup\$ And some, like Lattice Mach X02, have the flash on-board so you just need a few resistors and a 5x2 header to connect to the Lattice programming pod. \$\endgroup\$ – Spehro Pefhany Apr 10 at 18:59
  • \$\begingroup\$ I was aware you can program the flash directly via JTAG from tools like Vivado/Quartus, what I was hoping was to be able to do it without needing to purchase a vendor-specific cable--just use an FT2232H and write the bitstream (not bitmap?) myself. I don't think that chip is supported by Quartus, though, and isn't openly supported by Vivado (even though they use it on the Nexys and Basys boards). \$\endgroup\$ – Blake Lucas Apr 10 at 19:53
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    \$\begingroup\$ Yes, you can program the flash with the bit file using other means. One of your programmers for your MCUs can probably do it. I know my Segger J-link certainly can. \$\endgroup\$ – Toor Apr 10 at 19:56
  • \$\begingroup\$ @Toor: Indeed that's not a vendor-specific cable, but it still has hardcoded support in the vendor tools, and the Segger is quite a bit more expensive than a FT2232H. \$\endgroup\$ – Ben Voigt Apr 10 at 22:09
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    \$\begingroup\$ Pretty much all the major vendors provide engineering documentation to let the determined upload bitstreams to their parts (both FPGA and custom config flashes) with custom tools, because it is sometimes desirable in integrated systems or test rigs. It may be simplest to use the vendor's supported gear (especially at first), but I've implemented alternates for specific projects a number of times over the years. The harder part of an original FPGA board project may be all the support an FPGA needs on the board - lots of power pairs to route and bypass, often for several distinct voltages. \$\endgroup\$ – Chris Stratton Apr 10 at 22:22
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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.

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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.

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  • \$\begingroup\$ Obviously an SD card will not work, since no FPGA (to my knowledge) supports SD/MMC as a configuration protocol. Most FPGAs stick to AT24/AT26/AT45. \$\endgroup\$ – Dmitry Grigoryev Apr 11 at 13:09
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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.

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