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Author Topic: GekkoScience BM1384 Project Development Discussion  (Read 145267 times)
Finksy
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April 04, 2015, 01:39:05 AM
 #361

Aren't we all in the same boat!  Mining for information on the internet came way before mining for bitcoins for this guy.  I miss playing games, but life happens.  Family, responsibility, and other fun projects are way more important to me.

Anyone else grow up in the heydays of Quake TF? Man I miss those times...

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quakefiend420
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April 04, 2015, 01:46:48 AM
 #362

Aren't we all in the same boat!  Mining for information on the internet came way before mining for bitcoins for this guy.  I miss playing games, but life happens.  Family, responsibility, and other fun projects are way more important to me.

Anyone else grow up in the heydays of Quake TF? Man I miss those times...

See username.... Wink
sidehack
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April 04, 2015, 01:49:09 AM
 #363

If I had a family I'd probably prioritize it above building awesome stuff.

I actually was asked about bitcoin by a guy at church about two years ago, and knowing nothing about it, I looked it up when I got home and spent about two days reading.

Additionally, about to test the Compac regulator circuit. Taking all bets - work, smoke or fail?

hurricandave
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April 04, 2015, 01:55:07 AM
 #364

Time to get out the CamCorder!
TheRealSteve
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FUN > ROI


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April 04, 2015, 02:40:10 AM
 #365

Additionally, about to test the Compac regulator circuit. Taking all bets - work, smoke or fail?
Fail @ BTC0.01 ( don't mind losing that bet - though I hope it's not because it ends up being a release of the magic blue smoke )

sidehack
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April 04, 2015, 02:56:34 AM
 #366

Well the good news is it appears to work. There was no smoke, which I was actually expecting. But I need to do something about the high-frequency ripple on the output because it's killing the overvolt protection trip once the current gets very high. So some of the good news is, the overvolt protection works. Though I think a lot of what I'm seeing is actually ground noise on account of jumper wires since this is only a one-sided board.

Yep, better grounding and killing some added capacitance on the feedback loop is helping. I'm not exactly stable but it's at least working now with 740mV output (the top end, not bad since the calculated top end was 750mV) and 0.83 ohm load. So only 890mA output, or about 0.66 watts. The input power is approximately 5V 160mA, so 0.8W, giving this an efficiency of a bit over 80% at that low power. Which ain't bad because the peak efficiency should be about 3A output and at low currents the controller's probably in diode mode (or worse, forced CCM) so low-end efficiency is expected to suck. I should see at least 85% for most of the load range. Increased output capacitance with low ESR should help the ripple. There's tweaking to be done but so far I'm quite optimistic. Tomorrow I'll load-test it up to several amps and then see about strapping it on a populated BM1384, see if I can't get a chip talking to cgminer and then we'll be seriously rolling.

valkir
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April 04, 2015, 03:28:52 AM
 #367

Great job sidehack. cant wait to see the final product.
 Grin

██     Please support sidehack with his new miner project Send to :

1BURGERAXHH6Yi6LRybRJK7ybEm5m5HwTr
TheRealSteve
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April 04, 2015, 05:28:44 AM
 #368

There was no smoke, which I was actually expecting. But I need to do something about the high-frequency ripple on the output because it's killing the overvolt protection trip once the current gets very high.
So I owe you BTC0.005?  Fair enough Wink  Sounds like good progress all around Smiley

hurricandave
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April 04, 2015, 09:00:53 AM
 #369

So, six stick's with extra cheese  Roll Eyes
sloopy
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April 04, 2015, 04:58:57 PM
 #370

Sidehack I am sure you have plenty of people ready to throw their money at you, but please add me to any list you may make in the future as interested in buying at least two of everything you release. If you end up with anything not already promised for field testing I will gladly pay for those as well.

I feel that way because of your attitude to the community, the support you have shown me, and my own love of the tinkering.
So seriously please keep me in mind. I know some of my questions are n00bish but it is because I like to ask about everything and anything to see what experienced folks think.

I am also not that far away from you guys. I have techs driving between Moberly, MO and Tulsa to NE Oklahoma in the Bartlesville area all the time. I used to make those trips and love driving the windy, hill roads through MO. 

Good Luck and don't let the smoke out!

Transaction fees go to the pools and the pools decide to pay them to the miners. Anything else, including off-chain solutions are stealing and not the way Bitcoin was intended to function.
Make the block size set by the pool. Pool = miners and they get the choice.
sidehack
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April 04, 2015, 11:10:30 PM
 #371

Tested the regulator up to 750mV 5A, which should be able to run between 9 and 10GH. Regulator power at that point is 4.34W, so factoring in power for the rest of the stick you're probably looking at 4.5W or so to get there.

At 650mV I tested up to 5.2A, which should run 10-11GH off a regulator input of 3.94W, so probably about 4.2W input. Past 650mV with the .125ohm load, I'm not sure what was kicking on (internal OCP shouldn't have been a factor yet, nor should OVP) but the chip was shutting down then ramping back up rapidly.

I'm still not satisfied with the output high frequency ripple, nor am I impressed with the load regulation. Probably an artifact of the switch noise on the output getting through the feedback compensation is causing the output voltage to increase with output current. I didn't notice it until about 2-3A output, which means it shouldn't be a factor for a stock USB power range, but this thing's supposed to be designed to obliterate USB power if the user wants it to. I just don't want someone to crank up the clock on a particular voltage setting and then find out the voltage jumps up to shutdown point.

It's probably good enough to start initial testing with the chip, though. I'll wire up a breakout board and see if I can't get cgminer talking to an ASIC before clocking out tonight.

sidehack
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April 05, 2015, 03:55:31 AM
 #372

So, the chip is mounted on the board and receiving serial data and running off the Compac regulator. But it's not sending any serial data and cgminer doesn't recognize it. That's not terribly surprising, really. I'm hoping Novak can software up an answer for convincing cgminer to recognize it, or I find yet another hardware issue with my serial level shifter or something.

It did once report an Icarus error wrong device detected something or other, and occasionally it throws LIBUSB stop errors on unplug, but nothing has been consistent.

Anyway, right now it's quittin' time.

Searing
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Tips for help? 1BzbfMHCrTeLjc7eCGrYVhH3QXSRodSuke


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April 05, 2015, 04:08:27 AM
 #373

So, the chip is mounted on the board and receiving serial data and running off the Compac regulator. But it's not sending any serial data and cgminer doesn't recognize it. That's not terribly surprising, really. I'm hoping Novak can software up an answer for convincing cgminer to recognize it, or I find yet another hardware issue with my serial level shifter or something.

It did once report an Icarus error wrong device detected something or other, and occasionally it throws LIBUSB stop errors on unplug, but nothing has been consistent.

Anyway, right now it's quittin' time.


thanks we appreciate your efforts...i have no idea what the frack you are talking about..but find it 'soothing' none the less....hope it succeeds I need a 'toy' even at a loss on coin
vs what it could mine for when you get it out........I'm a sucker for the shiny LCD's and cgminer in putty....heh .....soothing... Smiley

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sidehack
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April 05, 2015, 04:19:04 AM
 #374

I guess at some point I should make a chart of the page of power data I got from the regulator. I'll probably make it better and then have to run all the tests again, but today I got output ripple and efficiency info from about 65 current/voltage setpoints before jacking with the BM1384 breakout board.

I'm really hoping there's nothing wrong with the chip itself and there's some trivial reason I'm not even seeing serial return data. I might reflow the chip tomorrow and shift it around a bit, make sure all pads got good solder contact. Any software poking that'll have to be done to cgminer driver will probably have to wait until at least Monday, if not later.


novak@gekkoscience
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April 05, 2015, 04:23:19 AM
 #375

So, the chip is mounted on the board and receiving serial data and running off the Compac regulator. But it's not sending any serial data and cgminer doesn't recognize it. That's not terribly surprising, really. I'm hoping Novak can software up an answer for convincing cgminer to recognize it, or I find yet another hardware issue with my serial level shifter or something.

It did once report an Icarus error wrong device detected something or other, and occasionally it throws LIBUSB stop errors on unplug, but nothing has been consistent.

Anyway, right now it's quittin' time.

Yeah I've not yet written a cgminer driver but I'll go through and see what's required to convince cgminer to accept it as a U3 or something similar. 

I think a couple things would need to be done:

Probably cgminer can't detect the component because some static setting in either the chip or cp2102 doesn't come up with something it recognizes- even the U3 was BM1382 after all.  I can probably fix that quickly by looking at a few settings on existing miners.

I'll have to figure out how the heck to get timeouts and whatnot working, I see different values on a lot of settings for AMU and AU3 which leads me to believe that this newer chip will require at least some changes.  That... Might require almost nothing or it might be complex.  Hopefully the chip will at least start up with U3 settings even if it runs poorly.

--
novak
sidehack
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April 05, 2015, 04:30:20 AM
 #376

I believe there's timeout data in the datasheet, for what that's worth. I'll have to clean up the Vcore regulator a bit for you but the thing should be pretty movable from one bench to another. Those breakout boards turned out pretty nice. Remains to be seen if they work properly though.

richardamullens
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April 05, 2015, 06:47:21 AM
 #377

Although I do not expect it, it would be interesting to see the schematic of your power supply design.

Although it is a completely different beast, there is a schematic for a software controlled DC-DC converter at http://www.ti.com/lit/ug/slau597/slau597.pdf page 36 - for the new MSP432 launchpad.

I pretty much gave up on switched mode power supply design many years ago when I found that the 25V EPROM programming voltage I generated had a 1 microsecond 14V overshoot that instantaneously killed my EPROMs.
sidehack
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April 05, 2015, 02:54:38 PM
 #378

Yeah, efficiency on that circuit would be pretty bad especially for low-duty-cycle applications. Also it's microcontroller-based, which can get tricky with software-defined frequency response if you want it to be really stable. A proper dev and testing of the code would take me a lot longer than just using a TL494 to do the same thing at least as well.

I measured the peak-to-peak ripple on our regulator, and also the peak overshoot, which would be on the charts. Typical instantaneous overshoot (which is a peak maybe 50-100nS wide) was less than 100mV. A bit of topography change and a high-frequency shunt capacitor, and some more bulk capacitance (I found my 47uF 1206 caps after I'd already full-range-tested it with some 22uF) would help smooth it out quite a bit.

One noteworthy thing was when the driver chip shifted into synchronous mode instead of skip/diode mode, usually around 650mV at low loads but as the load currents increased into the ranges these things will actually be running at, that threshold dropped somewhat linearly down below 600mV and by the top-end measurement it was starting in synchronous mode. This had a measurable effect on both efficiency and output ripple, as continuous conduction with a synchronous rectifier is way better than low-side-diode pulse skipping with hysteresis.

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April 05, 2015, 03:38:22 PM
 #379

Thanks for the technical information Smiley
I am of course interested in what you are making - or I would not be here - but I think that switched mode design is very important for many other things - e.g. LEDs for hydro/aeroponics and electrolytic purification of Copper where, I believe a cell voltage of 0.25V is used - hence my interest in software design in place of standard chips.
sidehack
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April 05, 2015, 08:09:08 PM
 #380

Right, switchmode is used in just almost everything these days. But a mathematically assured analog hardware solution I will always prefer over a software-only solution, especially where high speed frequency-dependent response is concerned. Why do an ADC sample and FFT and whatever else convolution processing for transfer functions when you can just put proper RC filtration on the line and be done with it? Everyone loves complexity these days, but complexity usually substantially decreases reliability and I'd rather have something reliable than something fancy any day.
Our TypeZero boards will have software-settable voltage control, but not because we have a fancy digital regulator. So far I'm designing around a flexible and reliable analog SMPS chip and probably put a DAC reference on it to do software adjustment. The stick miners don't need software-defined voltage. The complexity for that scale is stupid, so I'm just putting a smal trimpot on instead.

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