Ultra-Low-Cost DIY FPGA Miner - 175MH/s @ $1/MH

[rph]

Skillet-reflowed and ultra cheap. No need to pay $500+ for an eval board or $50+ per chip to an assembly house;
high performance FPGAs can be soldered at home in 5 minutes with some flux and a $20 skillet.

It's a xc6slx25 on there now to validate the PCB + asm process; building xc6slx150 soon.









-rph

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[thirdlight]

I'm not smart enough to know what I'm looking at, but it looks good

[322i0n]

Skillet-reflowed and ultra cheap. No need to pay $500+ for an eval board or $50+ per chip to an assembly house;
fgg484 can be soldered at home in 5 minutes with some flux and a $20 skillet. Grin

It's a xc6slx25 on there now to validate the PCB + asm process; building xc6slx150 soon.

I am not smart enough to understand what i read but it sounds interesting.

could someone translate for me?

[Dexter770221]

I had exact same idea... But I wanted to use LPCExpresso with LPC1769 for ethernet connection
175MH/s with SLX25???
Only one missing thing are holes that may be useful to mount a heatsink...

[heavyb]

If you can produce these I will buy them if they are really as "super cheap" as you say! I would but 5 for $175.

[heavyb]

how are these used? I am still trying to wrap my head around these, I am assuming the builder programs these chips specifically for mining, but do they plug into your monitor etc? how are they monitored?

[BombaUcigasa]

Skillet-reflowed and ultra cheap. No need to pay $500+ for an eval board or $50+ per chip to an assembly house;
fgg484 can be soldered at home in 5 minutes with some flux and a $20 skillet.

It's a xc6slx25 on there now to validate the PCB + asm process; building xc6slx150 soon.

1$/MH? Why don't you prefab these, including the addon boards into a new neat package and sell them?

http://it.rs-online.com/web/p/fpga/7276024P/ (47$-63$ per chip)
http://avnetexpress.avnet.com/store/em/EMController/Programmable-Logic/FPGA/_/N-100235?action=products&cat=1&catalogId=500201&cutTape=&hbxSType=New%20Search&inStock=on&langId=-1&myCatalog=&proto=&regionalStock=&rohs=&storeId=500201&term=xc6slx25&topSellers= (40$-60$ per chip)

The rest of the components cost 115$-135$? Are you sure you mentioned the right chip that does 175MH/s?

I'm in the wrong business, I would love to build final boards for these...

[norulezapply]

Would love to buy/build a few of these if I didn't suck at soldering so much. Maybe I can get someone to solder it for me.

[MaGNeT]

That's cool

[ArtForz]

Some of you guys have a reading comprehension problem?
The LX25 is just for testing a new layout and reflow process. If it doesn't work it was cheaper than a LX150. If it does work you get a LX25 on a nice 0.1" breakout board.
And yea, at low qty and without assembly $175 for LX150+discretes+board looks pretty much right.
Also, LOL @ that toy heatsink. a 25*25*15 is barely enough, better to use a 30*30*20 or even a 40*40 if there's space for it. and you'll still need quite a bit of airflow.

[deslok]

Do a demonstration video for us with the lx150, if it's as you say i'd be willing to buy assembled units at 225-250 depending on shipping and lead time

[rph]

Exactly as ArtForz said: the slx25 (~20MH/s) was selected b/c if something went wrong, it's "only" $40 down the drain. But it worked on the first try, with
even less hassle than leaded packages like LQFP48. And it proves the boards, assembly process, power supplies, and software work. Now it's relatively easy to
assemble more with the 6s150 (~175MH/s).

I want to vastly improve FPGA MH per $, for people willing to do the soldering (and thus take the mfg/yield risks) themselves.
It should not cost $400+ to mine with a $175 FPGA!

-rph

[dunand]

I'm not really happy about this. I live in Quebec and electricity is cheap. Affordable FPGA kind of destroy this advantage.

But this is really a cool diy. Good work rph !

[rph]

Some more details on the FGG484 BGA assembly:

Supplies
-------------
1. IR thermometer rated to 260C+ such as http://www.amazon.com/gp/product/B002YE3FS4
2. Electric skillet, like the one used in this Sparkfun tutorial: http://www.sparkfun.com/tutorials/59
3. No-clean flux syringe, such as Digikey SMD291-ND
4. Soldering iron [to pre-wet the PCB]

Calibration
---------------
1. Place an unpopulated PCB on the skillet, near the edge, directly over the burner coil.
2. Set the skillet to max.
3. Aim the IR thermo at the center of the PCB's BGA footprint and record temperatures every 15-30 seconds, as it heats to ~250-260C.
4. Plot the temp in Excel and compare with the IC mfg recommendations.
For Spartan6, that's http://www.xilinx.com/support/documentation/application_notes/xapp427.pdf.

If you're lucky the skillet will produce a good temperature profile on its own. The $20 Target skillet I bought 3 years ago
is almost perfect - just set it to max, and it will reach 250C after 4-5 minutes with a small PCB. It meets all of the Xilinx
guidelines, probably better than some professional assembly equipment. If it's way off, you might have to let everything cool down &
repeat a couple times with different setting. Or buy an MCU/Triac reflow controller. You don't have to match the temp profile
exactly, but obviously, the closer the better.

Assembly
---------------
With the profile set, I followed the prep instructions here: http://www.fpgarelated.com/usenet/fpga/show/39160-2.php
and monitored the FPGA with the IR thermo. Once the top of the case reached ~250C (~4 mins in)
I turned off the skillet, and used a fan to cool it down to ~100C over 4 minutes.



Checked it for power supply shorts, hand-soldered the bypass caps, then wired it up the LPCXpresso,
and it downloaded right way.

Sooner or later I will probably lose an FPGA through this process. But my bet is that it won't happen
often enough to justify the ~$50 per BGA fees for low-volume professional assembly.

-rph

[eldentyrell_old]

Congratulations and great job!

Just curious: are you actually mining on the chip, or is this just confirmation that the JTAG works and you're able to upload a bitstream?

I ask because designing a stable, properly-decoupled power supply for FPGAs isn't always easy... although for something as small as an LX25 you can get a way with a whole lot.  The Spartan6-150 with a full chip design (~50% LUT/FF usage) at a decent clock rate will be a good test.

  -ec

PS, speaking of clock rate, where's the clock signal coming from?

[phorensic]

I'm getting excited with all these new FPGA miner projects being announced.  This looks like good work as well!  Never knew you could reflow with a skillet haha.

[sadpandatech]

Do a demonstration video for us with the lx150, if it's as you say i'd be willing to buy assembled units at 225-250 depending on shipping and lead time

This +1

But, I'd be happy to see a demo video of the current lx25 mining on its own as shown just to verify functionality.
 I for one, would be willing to donate towards your purchase of an lx150 to then build and demo IF you can further verify your current work.

It looks fuggin great from what I can see here btw!  

[rph]

Just curious: are you actually mining on the chip, or is this just confirmation that the JTAG works and you're able to upload a bitstream?

I ask because designing a stable, properly-decoupled power supply for FPGAs isn't always easy... although for something as small as an LX25 you can get a way with a whole lot.  The Spartan6-150 with a full chip design (~50% LUT/FF usage) at a decent clock rate will be a good test.

PS, speaking of clock rate, where's the clock signal coming from?

It'll be another 1-2 days before the 6s25 is mining; I'm still finishing the RTL + SW.
I was so excited that the BGA assembly worked that I couldn't wait to share 

On the 6s150, I'm waiting for the carrier PCB to come back from fab. With luck, there
won't be any power supply issues. In some ways, miners are simpler and less demanding
than many other FPGA designs: VCCInt power consumption is almost constant once it's
running, and there isn't much IO activity [OTOH, VCCInt power consumption is very high...]

To minimize cost, the clock is provided by the MCU PLL & clkout pin.

The FPGA is downloaded by the LPC MCU over USB (slave serial).
The AVR board + USB serial cable is just there to provide power,
and program the LPC.

-rph

[rph]

Sounds great. Will you make and sell them?

Dunno yet. I've been reducing costs very aggressively and there's a chance the design
might not even work with 6s150. I need another 1+ wk of bringup/validation before
considering a small build for other developers. No pre-orders/etc at the moment.
Will keep you guys posted.

-rph

[Dexter770221]

This project is not for ordinary people. Good practice with solder iron is recomended. Not to mention that this is without a PSU. You need to build a 1.2V 5+A PSU and thats not easy and cheap. Costs are low but you need to invest your time to get this running.