Introduction: ESP-8266 12F Barebones to USB-to-serial

Having used a NodeMCU v1.0 ESP8266 ESP-12E module already, I decided I was ready to fiddle with a more "bare bones" setup, so that I could accurately breadboard and then move only the components I specifically need to a PCB prototype.

In too much of a hurry, I ran to my electronics store, bought one single 12-F (longer range!) and a USB-to-Serial converter, which happens to be of the sort designed to plug into the generic ESP-01 boards. Unfortunately this USB-to-Serial feller has no markings on it whatsoever. I had to stare for a while at the back of an ESP-01 pinout diagram to work out how to get mine wired up correctly. This instructable should help you to avoid doing the same.

Step 1: Make a Spider!

First off, I needed to reach the pads of the ESP unit. I know breakout boards exist, and I have ordered some to go along with my future units, but patience is not one of my virtues. I have a lot of CAT5e lying around, so I stripped some down, and bridged from my ESP pads to the back of some SIL pins (header pins) so that I could make it breadboard friendly.

Unfortunately I didn't take loads of photos, but you can see in the first image that I soldered the wires from the bottom first, clipped the excess that was sticking through, and then stripped the shielding from the other side before soldering to the top of the SIL pins sticking through my perfboard.

Step 2: Wire the USB-to-Serial

Now I needed to connect the ESP to serial, so I could do things like flash it or run AT commands. Here's the little header I made for the USB-to-serial feller, and matching connections plugged into the breadboard. There are notes on the second image to show you which wires come from the header.

In case you're trying to connect another USB-to-Serial device, but somehow wound up here, the connections are:

  • Yellow - TXD
  • Green - RXD
  • Orange - GND

From this point onwards, you can follow like I did, but ignore all the Arduino references and connections.

Some very important (but very subtle) points from that instructable are:

  1. The 10K Ohm resistors DO matter. Mine would not let me flash it without them.
  2. It's very important to switch the GPIO0 to pull-down (i.e. connected to ground) and either reset the device or switch it off and then on again.
  3. When I received my ESP-12F, it would not boot properly, it needed to be flashed (i.e. did not have an AT firmware flashed to it already like some do).
  4. My unit was running on 78440 baud rate, but I could flash it at baud 115200 without any fancy settings or pin connections.