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Comment by teruakohatu | Hacker News Reader

What kind of applications are these very low cost, low gate, FPGAs used for?

One real world example: The pebble time used a small FPGA to act as a display controller for their custom ePaper-like color LCD display.

Allowed them to interface with the non-standard display on a cheap off the shelf microcontroller, without having to waste power bitbanging. As a bonus, the bitstream also included the startup splash screen which would show instantly, before the cpu even got around to initializing the display controller.

>The pebble time used a small FPGA to act as a display controller for their custom ePaper-like color LCD display.

Minor correction: the pebble time uses a standard off-the-shelf Sharp Memory LCD display[0]. These displays are commonly used on smart watches so they're not propriety to Pebble. Sharp ships these displays as complete modules, with all control logic built-in, so you just need to supply power and serial commands to drive them. Any standard microcontroller can drive these.

You're right that Pebble chose to put an FPGA between their main microcontroller and the Sharp Memory LCD though.

[0] https://www.sharpmemorylcd.com/

And, what rate can you clock them at?

You can use these to replace a microcontroller doing a simple job it was not fast enough for, or burned too much power for, or you can't buy any of just now.

It feels funny to write this, because we used to say you could put a microcontroller in, in place of custom logic if it was fast enough. The best 6502 project I have seen put an 80MHz microcontroller on a 40-pin DIP format board, that bit-bangs out a 6502 on the pins. It has enough RAM to copy 64k in and execute from, where timing isn't critical.

That sounds like a fun project.

Here's a Z80 variant: https://j4f.info/z80-mbc2

Fabio has also done boards for the NEC V20 and 68K

What a clean design. I wished my 'daily driver' had such easy interface options for hardware.

>And, what rate can you clock them at?

High occupation projects on iCE40 LP1K (closest thing) easily clock 70-100MHz in my experience.

We can guess, but that seems pointless.

Look at Lattice’s marketing material. They have tons of applications covered. Mostly protocol converters, level shifters, all sort of glue logic, gate drivers an so on.

Hooking up two otherwise incompatible busses. For example, say you want to connect an SPI flash device to something that only supports NAND flash - you might use one of these FPGA's to act as a kind of converter.

Not an EE but I know exactly what I'm going to use these for: Playing with old CPUs so that I can implement all the bus and decode logic and some peripherals in it. Something like this[1] but even simpler. They'll probably be used for similar but more realistic stuff, i.e. as reconfigurable glue.

1. http://www.mattmillman.com/projects/8od/

Why not simply get one of the many cheap development boards that are available right now and with much larger FPGAs instead of waiting an unspecified amount of time for these?

These devices are painfully small for something like this and it is not clear whether they have any hard adders and multipliers.

yosys and minimalism mainly. As a hobbyist, I like to work with as little as I can get away with for fun and art.

I think professionals will be more interested because of the price.

Fair enough!

Probably custom high speed interconnect or glue logic that cheap MCUs cannot do. This is in relatively high demand given the current chip shortage. If this can do in-circuit programming, it’s huge.

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