Decision matrix for small MCU with onboard WiFi

I've trying to branch out into learning IoT, and have purchased a few different boards, and learned some lessons on the way. Now, I'd like to throw out here what I've learned, and see if anyone can steer me in a better direction, or refine the path that I'm on.

First, the boards:

  1. Adafruit Feather Huzzah ESP8266
  2. Hiletgo NodeMCU ESP8266
  3. Arduino Nano and ESP8266 ESP-01 breakout

All of these boards are currently on the breadboard, with a 3.3V/5V power supply module.

This is where the problem begins. Of all the boards, the one that I currently like the best - the Adafruit Huzzah - isn't recommended for external power supply. It is recommended for either battery or USB. That's not gonna work for me, because I want to pull power off of the Power Supply Module, to create a bus for everything. So the Adafruit site says:

" * Connect an external 3.3V power supply to the 3V and GND pins. Not recommended, this may cause unexpected behavior and the EN pin will no longer. Also this doesn't provide power on BAT or USB and some Feathers/Wings use those pins for high current usages. You may end up damaging your Feather."

The first problem is, I'm not quite sure how to make a decision on whether to ignore the recommendation, because I'm not quite sure what the EN pin is, or what it would do for me.

I don't really care about the USB. Will never use it, except for programming. And then, I'd just unplug the power supply. Other than this minor power supply issue, I think this board probably does everything that I want it to do. Anyone have any warnings or red flags, regarding this board choice?


Second favorite board, is the HiLetgo NodeMCU. Everything super straightforward (I think) about this board - the BIG problem, is that it only has one analog pin. I'm not really excited about multiplexing, or anything that requires a higher part count, if I can help it. I have a project idea that has 3 analog sensors, and I cannot find an I2C replacement for any of them. So this is a hard sticking point.

Power supply super straightforward. Vin for 5V, and GND, right off the power supply. Done.


Least favorite, is the Nano with the wifi breakout. I don't like this arrangement, at all. The Nano seems to be a good little board, but I really want an integrated WiFi board. If I can't resolve my major issues with one or both of the other boards, this is my backup plan. Of course, I'd still love to hear about any challenges with this one.

Power it through the USB connector, using a 5V power supply. To do so, cut a USB cable with the appropriate connector and identify the power and ground leads. Or use a phone charger.

I'm not quite sure how to make a decision on whether to ignore the recommendation

In such cases, don't ignore the recommendation, because you lack the understanding to get it right.

Rather than cutting a cable, would a small run of USB from the power supply module, to the board work? So I have my 9V supply plugged into the jack, the supply module regulates 3.3V and 5V for the bus, but the USB on the supply module - rather than being a power in - could it backfeed, and thereby power, the board?

Post a clear, focused picture of your setup.

I can't make much sense of that word salad, except to wonder why you would think it a good idea to use two power supplies at once.

This will also be a problem with the Huzzah (IIRC) :

The Nano hybrid, of course, will have 7 analog pins but post a link to it. It may even be that you use AT commands from the Nano to talk to the ESP8266 based module.

LOL. Words aren't for everyone.

I'm not talking about using 2 power supplies. I'm talking about something like this - THIS is the general ideal.

Maybe I'm not understanding, but here is the page that describes the pinouts. The Huzzah seems to have plenty of Analog.

I don't need regular digital pins, so this works nicely. I use I2C as much as I can, and of course, those connections can piggyback.

Yes the ESP32 based Huzzah does indeed have more Analog pins. However, you mentioned the Huzzah ESP8266 in your OP. Then it is clear, Go for the ESP32 Huzzah.

D'oh! You're right about that...

So in looking, I do have the ESP32. Apologies for the misdirection.

So back to the question about backfeeding from the USB on the power supply module... I cut the end off of a USB cable, and took a reading from the power and ground...

So is there any compelling reason NOT to do this?

So back to the question about backfeeding from the USB on the power supply module

The little board is a voltage regulator, not a "power supply module".

You could power the entire setup using a phone charger, as already suggested and dispense with the voltage regulator board.

That "little board" is sold everywhere as a "power supply module". I did not invent the terminology.

My question was not about using a phone charger. It was about the feasibility of the method that I provided the picture for, per your request. A simple yes or no would suffice - although I'm not opposed to a simple, word based explanation, of why it would, or would not, work.

When you buy cheap Chinese crap on eBay or Amazon, you should not expect the sellers to use the correct terminology.

If your setup works, use it. It is still not clear what you are trying to do, but the "backfeeding" term makes no sense.

The schematic of the Adafruit Feather Huzzah32 is here https://cdn-learn.adafruit.com/assets/assets/000/041/630/original/feather_schem.png?1494449413 . Supplying exactly 5 volts through the USB socket of course works.
You can use the vBus pin also to deliver 5v to the module.

Well I'm not here for a "Buy American" campaign. I'm building simple, indulgent gadgets, that don't require a failure probability analysis. This isn't product design, sir. It's just a hobby and learning platform, that will most likely never see a professional application. So I'll buy that "cheap Chinese crap", as often as I can, and lose little, in the process. And as long as we're all being consistent, consistently wrong will still be more understandable to the majority.

If the term "backfeeding" doesn't make sense to you, after both an explanation and a picture, then maybe you're not the right person to answer the question. I'm not able to be technically semantic about it, so you'll forgive me for using what I know. You haven't really offered me a better term, so...

Let's start over.

That's not gonna work for me, because I want to pull power off of the Power Supply Module, to create a bus for everything

What you have is a voltage regulator board, which takes power from somewhere else, and provides 3.3V and 5V outputs.

Use those 3.3V and 5V outputs as you see fit. To power the Adafruit Huzzah via the USB connector of that voltage regulator, do exactly what you are doing now. You can also cut that USB cable, take the piece that connects to the Huzzah, isolate the 5V and GND leads, and connect them to the 5V and GND terminals of the voltage regulator.

Good luck with your project.

Excellent. Thank you for your guidance.

My contribution:

My first Arduino project (and most challenger untill now) was a Bluetooth scale that I did for my wife.

I´ve started with an UNO + HC-05 module. Then dowscaled it to a Nano 33 IoT, but found it difficult dealing with Bluetooth Low Energy.

I ended up using this ESP-32 with 18650 battery --> http://www.lilygo.cn/prod_view.aspx?TypeId=50033&Id=1170&FId=t3:50033:3

Nano 33 IoT also has a built-in wi-fi, which would fit your requirements, but it´s also a 3.3V based board.

So, IMO, keep going with your ESP32 Huzzah.

Thanks for that advice!

So I made a quick little USB power connector, to experiment. However, I'm not getting anything like this.

When I power through the pins on the board, (Vin and GND) I get a voltage out of the USB connector. It's fluctuating between ~1 and ~2 VDC. However, when I try to power through the USB, as shown in the picture, I have no power, when tracing the 3v3 and GND pins.

I get 5VDC when I take a reading off of the screws in the terminal block.