First steps with the Pro Micro

If you build permanent projects, you want small, cheap Arduino boards that you can permanently integrate into the project. For 5 Volt projects, the Arduino Nano is perfect. However, these days most sensors and small displays are 3.3 Volt. The Pro Mini is great for such projects, especially for low power projects. However, it lacks USB, which complicates things. The Pro Micro comes with native USB built into the chip (32u4). This could be a great choice for simple 3.3V projects. I bought a few Pro Micro clones (3.3V, 8 MHz) to check it out.

The chip has only 2kB RAM which makes it difficult to drive small 128x64 pixel OLED displays (same problem as with the original Arduino Uno and Nano). Nokia5110 displays can be used without problems. (128x32 pixel OLED displays which are very small can also be used without restrictions).

The board has no reset button but at least there is a reset pin, so that a reset button can be wired up:

Installation of the board files in the Arduino IDE is described in detail in Sparkfun's guide.

In Windows 10, I did not have to install a driver. Plugged in, the boards are recognised as Sparkfun Pro Micro and appear in the device manager under ports:

From Sparkfun guide: In order to communicate serially, the Pro Micro emulates a virtual serial port. Actually, it emulates two different serial ports -- one for the bootloader, and one for the sketch. Since the bootloader and sketch run individually, only one of these serial ports is visible at any one time. To see the bootloader port, you have to press reset twice. The bootloader port will open for 8 seconds:

This is useful if you have "bricked" the Pro Micro, which happens a lot. Reset twice and then start uploading the code before 8 seconds have passed.

Upload the RX / TX blinky test code from the sparkfun guide with the help of the Arduino IDE.

Relevant links

https://learn.sparkfun.com/tutorials/pro-micro--fio-v3-hookup-guide#introduction

https://learn.adafruit.com/adafruit-mcp9808-precision-i2c-temperature-sensor-guide/overview

https://github.com/adafruit/Adafruit_MCP9808_Library/blob/master/examples/mcp9808test/mcp9808test.ino

https://cdn-shop.adafruit.com/datasheets/MCP9808.pdf

Test with Adafruit MCP9808 Precision I2C Temperature Sensor

As a first test, I connected a I2C sensor and uploaded the Adafruit test program (mcp9808test.ino):

This time, I used PlatformIO for the test. Here, I didn't need to install board files. I just started a new project and chose the correct board for the project (SparkFun Pro Micro 3.3V/8MHz). The program uploaded without any problems and worked immediately (although it was written for an Arduino Uno). The 32u4 managed to open the USB port and output the temperature to the pc or other devices (Android). This was certainly encouraging.

Pricing

As I mentioned, if you want to make your projects permanent, you want cheap boards that you can integrate into your projects. While you can easily get a Pro Mini clone for $2.50, I had to pay $5 for the Pro Micro clones. That is a high price point compared to other microcontroller boards:

Until now, I have mostly used Wemos D1 Mini and NodeMCU boards with their much more powerful ESP8266 chip for 3.3V projects. Not only do they have built-in WiFi but the boards also come with 4 MB of flash memory. Wemos D1 Minis cost about $2.50-$4 while the larger NodeMCU boards are in the range $3-$4.50. ESP3266 boards are thus slightly cheaper than Pro Micro boards. But they have a higher power consumption, which is often a drawback for small battery-powered projects.

Good alternatives to the Pro Micro are the Seeeduino Xiao ($5) and the Adafruit QT Py ($6), which are even smaller boards based on the SAMD21 chip.

© 2020 notthemarsian