ESP8266 Wemos D1 mini

A quick note regarding the ESP8266 based board named Wemos D1 mini.

I bought one of these boards, from Aliexpress for under 4€. It took more or less a month to arrive. I’ve still haven’t too much time to do something with it, but here are my first impressions:

The Wemos D1 mini is, in my opinion a better buy than the ESP-01 and ESP-12, for many things:

– It has all the supporting electronics for power and serial communication:
– Included USB to serial converter CH340G, but with no TX and RX activity leds.
– It can be powered by the mini USB connection, or through a 5V pin, since it has a 5V to 3.3V linear converter
– It also has a 3.3V input/output pin.
– It comes with some modern version of NodeMcu, so it’s ready to be used with the ESPlorer application, just connect to USB and we are ready.
– It includes stack able pins that allows several ways of creating our devices.

But most important is that it can be flashed with alternative firmwares, like Sming, and that’s what I did. Sming applications that I have, like the Wifi Scanner worked just fine and detected several wifi networks on the vicinity.

Also, the Wemos D1 mini has a reset button, but there is no need to use it to flash the device. The RTS and DTR lines of the serial connection are properly mapped to the GPIO0 and RST pins of the ESP-8266 so flashing is automatic. No need to press reset or manipulate pins. I was able to flash the device with several different bit rates like 460800 and 921600. The esptool.py can have some issues detecting the board, from some of the tests that I did, but at the end it flashes the board with no issue.

So, being the double of the price of the ESP-01 and a bit less price difference from the ESP-12, but with the included power and USB-Serial electronics, that are needed to be budgeted and implemented with the other boards, and all on a nice small package, it is by far the best way to enter the ESP-8266 world.

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5 thoughts on “ESP8266 Wemos D1 mini

  1. Did you need to do anything special with Sming to make the D1 mini work ?
    I just tired to load some code that works fine on a nodemcu, but the D1 is crashing …
    BTW – you have a great blog 🙂

    • Hi, no I didn’t do anything special to make my code working with the D1. I’ve just picked some code from some of my developments, like this one: https://github.com/fcgdam/ESP8266-Wifi-Scanner and flashed it and it just worked fine. At first the command make flash command failed to connect for flashing, but I’ve changed the bit rate to 921600, the make flash command started working. I’ve changed the bit rate because I’ve read somewhere that it was only possible to flash the Wemos D1 minie with that bit rate. But the fact is that I was able to flash it AFTER the initial flashing with 921600 with the 460800 bit rate. So I’m not sure if the way that comes from the supplier only allows first to flash at 921600, and then with Sming on board it can be flashed at any speed. As always, YMMV 🙂
      And thanks, for the compliment on my half baked blog (since english is not my native language, I imagine that Shakespeare is nodding is head in disapproval while watching me killing the English language…)

      • Hi – thanks for the hint on flashing speed. I’m getting a python error above 230400 – I will sort that tomorrow.
        I’m sure that you’re English is better than Mr.S. 🙂

  2. Hi – thanks for the blog.
    Do you know if it is ok to feed the RX pin from an external circuit? I mean this pin is already connected to the USB2Serial IC, so it will be driven by two circuits…

    • Not sure if the USB to Serial RX pin is an open colector with a pull up or not. If it is, then there is no problem. If not I’m not sure… 🙂

      Edit: The schematics are here Wemos mini schematics and it shows that are two serial resistors at the RX and TX pins, so it might be ok to connect something at the external pins.

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