In the previous entry of the ESP8266 section, we saw the NodeMCU. This time we will take a look at what is surely my favorite development board based on the popular ESP8266 SoC, the fantastic Wemos D1 Mini.
The Wemos D1 Mini is the smaller version of its big sister Wemos D1, which we will see in an upcoming entry. With dimensions of 34.2mm x 25.6mm and a weight of 3g, it is one of the smallest boards based on the ESP8266.
The Wemos D1 Mini is only slightly larger than using an ESP12 module directly and provides many advantages, such as incorporating a Micro SD port and serial converter, voltage regulator that allows it to be powered at 5V, and terminals to connect our devices.
In addition, the Wemos D1 Mini has the philosophy of allowing to expand the functionality through the connection of Shields. There is a wide variety of Shields such as motor controller, relay module, Oled screen, temperature or humidity sensors.
On the other hand, as a major disadvantage, the Wemos D1 Mini has a smaller number of available pins. It only exposes 11 GPIO pins compared to the 17 available on the ESP12 or the NodeMCU, although in most projects this is not a big problem.
Wemos Mini D1 Features
As we say, the Wemos Mini D1 is based on the ESP12E, so the characteristics come directly from it. In a very summarized way, these are some of the main features:
- Speed: 80MHz/160MHz
- Flash: 4M bytes
- Operating voltage: 3.3V
- Digital inputs and outputs: 11, all (except D0) with PWM, interrupts, and I2C
- Analog inputs: 1 (Max. 3.2V)
- Micro-USB connector
For the rest of the detailed characteristics, check the entry about the ESP12E
Price
The price is one of the strong points of the Wemos D1 Mini. We can find it for about 2-2.20€. Therefore, it is even more affordable than a NodeMCU and only slightly more expensive than buying the module alone (to which we would have to add the components, etc. ..).
That is, the Wemos D1 Mini has a really compelling price.
It should be noted that there is a version, the Wemos D1 Mini Pro (next image, on the right), which increases the memory to 16MB, which costs much more, between 4-5€.
Be careful if you try to buy a Wemos D1 Mini Pro, verify that it has 16Mb and not 4Mb, because some seller sells a physically identical model, but with 4Mb. That is, just like the “non-Pro”.
Wemos Mini D1 Pinout
As we are already used to, one of the biggest headaches we will have when working with development boards based on the ESP8266 is the lack of consensus in designating the pins. Therefore, it is even more important to have a good pinout diagram of the board nearby.
Here is the Pinout of the Wemos Mini D1:
And here is the summary table of the pins and their main function.
| Pin | ESP-8266 Pin | Function |
|---|---|---|
| TX | TXD | TXD |
| RX | RXD | RXD |
| A0 | A0 | Analog input (max 3.2V) |
| D0 | GPIO16 | IO |
| D1 | GPIO5 | IO, PWM, Interrupt, I2C, SCL |
| D2 | GPIO4 | IO, PWM, Interrupt, I2C, SDA |
| D3 | GPIO0 | IO 10k Pull-up, PWM, Interrupt, I2C |
| D4 | GPIO2 | IO 10k Pull-up, PWM, Interrupt, I2C, BUILTIN_LED |
| D5 | GPIO14 | IO, PWM, Interrupt, I2C, SCK |
| D6 | GPIO12 | IO, PWM, Interrupt, I2C,, MISO |
| D7 | GPIO13 | IO, PWM, Interrupt, I2C,, MOSI |
| D8 | GPIO15 | IO 10k Pull-down, PWM, Interrupt, I2C,, SS |
| G | GND | Ground |
| 5V | - | 5V |
| 3V3 | 3.3V | 3.3V |
| RST | RST | Reset |
Programming the Wemos Mini D1
Programming the Wemos Mini D1 from the Arduino environment is easy and simple, just like with the rest of the ESP8266 boards. The process is identical to what we saw in How to program ESP8266 with the Arduino IDE, so if you have any doubts visit this post.
We just have to make sure to choose the “Wemos D1 R2 or Mini” board:
So far the tutorial of this great board based on the ESP8266. As I said, it is one of my favorite development boards. With the price it has, we can afford to integrate it into any project. We will be back soon with more tutorials on the ESP8266 and more development boards based on it. See you soon!