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A project log for RPi WiFi

Fast RPi WiFi without USB

ajlittajlitt 03/04/2016 at 22:4924 Comments

With last week's release of the Pi 3B (with built-in SDIO WiFi!) came news that a A+ version of the Pi 3 is coming, and that Pi Zero production will continue to crawl along to keep Pi 3B stock moving. This gives me the jibblies about putting time and money into producing and selling the WiFi Pants board.

So: assuming a Pi 3A+ is coming within the next six months with WiFi, bluetooth, and faster CPU at the same price as the existing A+ ($20 USD), and assuming that the Zero is going to be hard to get at least until the availability of the Pi 3A+, would you still buy the WiFi Pants board for $20 USD?


txdo.msk wrote 03/09/2016 at 01:23 point

I'd definitely buy a few if there were an option for different BOMs based on functionality.  

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Mark Kuhlmann wrote 03/08/2016 at 20:29 point

$20usd puts it out of range for me only because the CAD/USD is so bad at the moment. If the dollar was better and brought back closer to on PAR , making it $20CAD, I'd have no problem.

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davedarko wrote 03/05/2016 at 17:37 point

it makes sense for setting up older generations and the zero, but tbh as well, 20usd is a bit above my paying willingness. Btw. I came back to my "design" based on your findings and made the most minimalistic board I could fit twice on a dirtypcb size. That's how cheap I am :D an esp12f, the resistors and a ld1117 with it's caps fit on it. If it works and I would get some money out of the boards then I'd of course get one though! 

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ajlitt wrote 03/07/2016 at 18:49 point

Thanks!  If I were going to buy one of these only for WiFi I'd have a hard time justifying it too.  I would probably buy just the module and p-t-p wire it. Oh wait, I have :) 

I while back I did a test layout of a Pants board without the boost and mirrored across the diagonal.  It would have put the ESP-12F under the SD slot as well, but would have dead space under the connectors.  It would have also been no cheaper at the company I'm looking at for boards (Elecrow), and not significantly cheaper in the face of shipping from Dirty.

I added the boost and left the UART header because they add unique value.  Due to its size, the Zero is good for portable projects, and a plug-and-play battery option saves developers from having to cram an extra board in for power.  Many projects won't need the boost, and for those it's a waste of money over hand-wiring an ESP-12F or a board like you propose.

You should ditch the linear reg.  I haven't had a single problem with my ESP-12F designs overstressing the Pi's 3.3v buck.  

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David Lowe wrote 03/05/2016 at 16:23 point

It's not just a WiFi board though is it, "WiFi Power Pants" would be a more descriptive name! Those that want the Zero form factor will pay $5+$20 vs an assumed $20 for the 3A which is twice as big, yes more bang, but no onboard boost supply.

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ajlitt wrote 03/07/2016 at 17:28 point

Thanks for responding.  Yes, that's why I asked rather than stepping away from the project.

I'm fairly impressed with how the TI boost converter is working, so even if I never make more than a few of these for sale a dedicated battery power HAT / Pants that could be used with the newer models might be something to do in the future.

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Patrick Van Oosterwijck wrote 03/08/2016 at 17:05 point

I'm sure the TI boost is a good part, but they tend to be spendy.  So if you want to reduce cost you could look at some lower cost competitors.  I've had good success with boost converters from

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ajlitt wrote 03/08/2016 at 17:37 point

Thanks  @Patrick Van Oosterwijck!  Yes, the TI parts aren't cheap but I haven't found any boost drivers that do >1A @ 5v from 3V in.

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Patrick Van Oosterwijck wrote 03/08/2016 at 18:41 point

On the 5V version of my #LiFePO4wered/Pi I'm using the MIC2876.  Only 3.8A switch versus 4A for the TPS6123x, but less than half the cost!  (Actually that's what Digi-Key claims -- the specs say 4.8A switch vs 5A.)  It seems to be working well for me, but I have only tested it with Pi's up to RPi2 plus a WiFi dongle.  Another advantage: it has a bidirectional load-switch, so things don't fry if you power the Pi from its own micro USB connector!

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Martin wrote 03/11/2016 at 12:46 point

Do you also think about selling naked PCBs of this PiZero - ESP12 solution?

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ajlitt wrote 03/20/2016 at 09:03 point

@Martin I just pushed the (hopefully) production board to github and ordered PCBs for building modules.  I should have extra bare PCBs to sell when I have built up some of the stock, which should be in a month or so.

But if you can't wait: 

Order from OSH Park

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Martin wrote 03/22/2016 at 14:36 point


Hello ajlitt, 

I am not in a hurry. OSH Park will deliver 3 boards for $15,- , including worldwide shipping as I understand. I would need only one piece, as I have only 1 Zero. :-) How much do you think shipping would cost, if I wait for one of your spare boards?

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ajlitt wrote 03/22/2016 at 15:12 point

@Martin I am still trying to figure out shipping, particularly international so I can't quote anything yet.

If you have a preferred board house, you can grab the latest KiCad files from github and roll your own gerbers to save a few bucks.  

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Martin wrote 03/22/2016 at 16:05 point

@ajlitt No, I don't have a cheaper offer than OSH Park, which fortunately has a very low minimum area, not something like 5*5cm or 10*10cm. I just wanted to ask, as I do not know postage values from USA to Europe. Perhaps it is really the best way to just order from OSH. Dirtypcb is one dollar cheaper but takes much longer time for shipping.

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Martin wrote 03/23/2016 at 08:27 point


Ok, so I finally ordered from OSH Park because it is really easy. :-) Thank you for your design work!

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tj wrote 03/05/2016 at 16:07 point

I'd like to pick one of these up as well; It seems like a great way to make my pi zero usable.

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ajlitt wrote 03/07/2016 at 17:22 point

Thanks for responding.  That was my original motivation: to take the Zero from a cheap curiousity to a practical embedded board.

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Stefan Lochbrunner wrote 03/05/2016 at 13:05 point

TBH, 20$ is a little steep for my budget but I'd be interested in the bare PCB. Maybe selling two or three tiers (the third tier being an unassembled kit) would be feasible.

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ajlitt wrote 03/07/2016 at 17:13 point

Thanks for the idea.  I may end up doing something like that.

The switcher is really the expensive part.  The IC itself in low qty cost me more than the ESP-12F, the caps and inductors are also expensive, and the increased component count and part density make it (likely) impossible to solder without reflow.  If you wanted to build one w/o the switcher you need the PCB, 6 33 ohm resistors, the connectors, and the ESP-12F.  

I plan to order PCBs soon, and if you were to order just the PCB you would have the option to solder down only the ESP module.  The WiFi and switcher are independent systems.

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Mubarak Abdu-Aguye wrote 03/08/2016 at 14:45 point

Building on what Stefan Lochbrunner said above, you could have a number of tiers. Personally, I'm not really interested in the switcher or its uses, just the WiFi bit. Though it'd be more work, could you design/provide a version of this board that is WiFi-only? That would also help drive the costs down significantly, so you could have:

Tier 1: Full board (WiFi + switcher assembled)

Tier 2: WiFi -only (assembled)

Tier 3: Bare PCB only 

Tier 1 would be the priciest, Tier 2 would be much cheaper (and I'm sure it'd be cheap enough for the majority of hackers out there since a few have raised concerns about the price), and Tier 3 would let you pick exactly what you want, while letting people with SMT expertise do their thing. I also have a couple of A+s, Bs and B+s, and I'd like to use this board to give them some much needed WiFi, kinda like Radomir Dopieralski below, except that I wouldn't need the power option. You've done a great job with this man, and there's absolutely no need to drop it because of the Pi 3. Or that's my opinion anyway.

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deʃhipu wrote 03/05/2016 at 13:05 point

I would be very happy to buy this for my robots. Not only will it give them wifi, but also a very nice power option.

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ajlitt wrote 03/07/2016 at 17:18 point

Thanks for the response.  So far the switcher is resilient.  I still haven't done real characterization on the power for lack of a decent bench supply, but I have successfully run a 60 LED WS2812 strip and a Zero off 3AAA NiMh batteries boosted without hiccups.  I think it will work great with small servos like on your Tote robots if you throw a big filter cap on 5V for good measure.

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Craig Hissett wrote 03/04/2016 at 23:07 point

Id still buy it mate. Yes, the new Pi 3 models have WiFi integrated, but that doesn't help me add WiFi to my current collection of Pi boards!

I have 2 x A+ boards and 3 x Zero boards that could all benefit from your pants board when they get out into a project, and I'm sure I'm not the only one that still plans on using current Pi rather than rushing out to get new ones!

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ajlitt wrote 03/07/2016 at 17:20 point

Thanks!  I can see sticking to the older Pis after reports of the Pi 3's power consumption.  The 2 isn't a lightweight either.

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