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Comment by xg15 | Hacker News Reader

Hang on, did he just buy essentially a freely reprogrammable FPGA with built-in RAM, A/D converter and USB support - for $20? Seems to me, you could do a lot more with those devices, now that the wire protocol is known.

(Edit) It doesn't appear that he decoded the bitstream format though, so some more work would be needed before you could use it as a general-purpose FPGA.

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Yeah, a 16K Spartan 6, 64MBytes of DDR3 RAM, and an FX2LP USB High-Speed controller is a pretty terrific repurposed FPGA dev board in the vein of the chubby75 or panologic, even if the high-speed ADC turns out to have too many limitations / too weird signal conditioning (i.e. is too VGA-focused) to be very useful (but VGA probably at least means a pair of I2C pins is exposed on the DSUB-15, right?). Considering the FX2LP is already wired up to load the bitstream to the FPGA, and expects to on every power-up, that's a huge bonus for a dev board. Even if the binary blob of FX2LP firmware provided in the manufacturer's drivers does checksums, signature checks, etc. to make changing the bitstream data difficult, it would be pretty simple to write a new firmware to allow uploading of any custom bitstream (see: fx2lib), since it's such a well-known and widely-hacked chip -- maybe you can even manage to trick Xilin's ISE into believing it's a real Xilinx "USB Platform Cable" (FPGA JTAG programmer) since at least some of them use an FX2 for their USB interface. With a generic bitstream uploader utility for the FX2 you wouldn't even need to deal with any hardware modifications or even need to buy and connect a JTAG programmer if you were just starting out. And with everything being uploaded on every reset of the devboard, you don't have to worry about bricking anything either, since you just power-cycle the devboard to bring the programmer AND FPGA back to their default waiting-for-firmware/"rescue" mode.

But while the article says he got a lot of them (at least 3 from the photo) for $25 total, it looks like they're more typically ~$50+S/H each on ebay, which is less exciting.

The same company seems to have moved on to 'av.io'-branded USB3 devices now, which from a quick glance/binwalk of the downloadable firmware package (inspired by this article) appears to have FX3 USB Super-Speed controllers, and Spartan FPGAs. But it's designed to store the FX3 firmware and FPGA bitstream on the device itself (to allow it to boot up as a UVC webcam with no drivers required on the host, like this article was hoping would be the case for the older device), so it would require a bit more reverse engineering to figure out how to kick the FX3 into firmware update mode to replace the FX3 firmware with a custom bitstream uploader. But it's a ton more expensive, and who knows what generation and size of FPGA or how much and what sort of memory it would have.

> Yeah, a 16K Spartan 6, 64MBytes of DDR3 RAM, and an FX2LP USB High-Speed controller

The last one alone, CY7C68013(A) has always been an expensive chip (like $10 a piece if you just want a few).

What is funny is that I wasn't aware it existed in QFP-56 package, it is not supposed to exist :-)

It's in a QFN not QFP package

QFNoWay

Worst package I've had the pleasure of hand mounting.

It's quite nice though when you consider it's really small without requiring difficult BGA mounting (QFN reflow is about as hard as QFP reflow).

It also provides superior electrical properties like low-inductance.

More IC manufacturers with hobbyist buyers should adopt "QFN - At Least It's Not BGA" as a slogan.

Unless I'm looking at the wrong thing, it seems like prices on eBay have jumped to ~200+

Correct, that's actually a pretty nifty piece of general-purpose hardware for the price. It's essentially an SDR (software-defined radio) for baseband, meaning it provides simultaneous sampling on three channels from DC to whatever a suitable Nyquist rate for VGA decoding would be. Several MHz at least.

The bitstream format isn't anything special. It's whatever Xilinx says it is for the Spartan 6. Any bitfile generated by ISE for the XC6SLX16 could be uploaded via the (generic) Cypress FX2LP chip.

This is all relatively old hardware, very well-documented and well-understood but still quite capable. It has a lot in common with the earlier-generation Ettus USRP receivers that used the FX2.

> Several MHz at least.

A lot more, actually. Manufacturer's specs for the ISL98002CRZ-170 [1] say it'll do 170 MSPS, with an analog bandwidth of 780 MHz. It's actually a rather impressive ADC! The question would be whether it can be convinced to sample continuously.

[1]: https://www.renesas.com/kr/en/www/doc/datasheet/isl98002.pdf

Stupid pedantry on my part: ADC.

Whoops! Corrected; thanks.

> The bitstream format isn't anything special. [...] This is all relatively old hardware, very well-documented and well-understood.

I wasn't aware of that. This is even better of course!

It was actually 20 pounds for 10 ish, so it comes out even cheaper.

Sadly it seems that was just a stroke of luck, since I can't find anyone else selling them anywhere near that cheap now

I have one lying around here somewhere... nice to know I can finally use it :)

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