This article is an attempt to clear up some of the confusion surrounding the wiring of those ubiquitous white ESP-12 breakout boards.
As with a lot of these parts flowing in from offshore factories, there’s good news and bad news.
The good news is that these boards are an excellent solution for breaking out the pins of your ESP-12 modules, making them usable on regular .1-inch spacing breadboards and PC boards. Also, the convenient onboard surface-mounted resistors save you some off-board wiring.
The bad news is there are mistakes on almost all of these boards. Specifically, the voltage regulator solder pads on the back of the board. Take note, the input and output pins are reversed!
I’ve included some hand-sketched diagrams tracing out the connections to help illustrate how these boards are wired, as I’ve yet to see a schematic or instructions or a wiring diagram from any of the vendors.
As is often the case with offshore electronics manufacturing, a design with a defect is replicated and copied exactly by multiple manufacturers, thereby flooding the market with faulty boards. All of the ones I’ve received have the same flaw. The following are a few tips that I hope will save you some time and frustration.
Some vendors even include an LM 1117-3.3 regulator that you can solder onto the board yourself. The idea is that you can use a battery or 9V AC adapter as the power source, without having to add an extra power circuit. This is great if you’re trying to save real estate to make a tiny project.
There are also three surface-mounted resistors on the board, including two 10K pull-up resistors. There is also a mysterious zero-ohm resistor in the middle, and people have wondered what purpose it serves.
It’s actually a jumper that shorts the input and output solder pads of the regulator, for when you’re not using one. If you are going to use the onboard regulator, then you must desolder the jumper resistor.
So like a lot of people, I soldered in the 3.3V regulator and applied a 9V battery to the board. Funny, I’m getting 9V at the ESP 12 module where I should be getting 3.3V.
What has happened is that without removing the zero-ohm jumper, I’d immediately shorted the regulator. It’s a moot point, as I also realized by tracing out the circuit that the regulator pins two and three have been reversed! Your ESP-12 may already be fried, long before you ever see that comforting purple flash of the LED upon power up.
This sketch traces out the circuit board wiring as I received them. As you can see, pads number two and three are reversed for an LM1117 regulator.
Best thing to do is leave the board alone and just use an external 3.3V supply. That way it works fine with the shorting resistor in place.
If you absolutely have to have a surface-mounted 3.3V regulator on the board, you’ll have to cut a few traces and run a jumper or two, as well as remove the zero-ohm resistor.
Here’s a photograph of the modification that seems to work fine. You’ll need to cut the traces at the red lines and solder in the jumpers as shown.
There has been some confusion as to the connection to GPI02. It is in fact GPI015 that is held low, and it’s just the way they silkscreen lines up on the connector that is a bit confusing.
These are the correct connections for the pull-up resistors. Just remember to remove the zero-ohm resistor if you’re adding a regulator.