In previous post I said that I need to find a way to reduce current draw for the digital clock project. I have watched several YouTube videos about low power Arduino, and they seem to have one thing in common: use Arduino Pro Mini instead of Arduino Nano. This makes sense considering Arduino Pro Mini lacks the USB to Serial chip, and uses more efficient LDO regulator. Other than that, the 3.3V/8MHz version of the Pro Mini also supposedly uses less power compared to the 5V/16MHz version.
I had never used the Pro Mini before. I searched the local online marketplace for the Pro Mini clones, and only the 5V/16MHz version was affordable to me. The 3.3V/8MHz version was twice the price. So I bought the 5V/16MHz version.
After soldering the header pins I immediately powered the Pro Mini. Apparently it was already pre-programmed with the Blink sketch, as the on-board LED was blinking.
First I tried the Fade sketch, which is a built-in example sketch from the Arduino IDE. I programmed the Pro Mini using a USB to TTL converter with CP2102 chip. The pinout for connecting the USB to TTL converter with the Pro Mini is straightforward, so is the settings in Arduino Nano. This article explains how. I say straightforward, but definitely more work compared to Arduino Nano. In any case, everything worked as expected.
Next I tried the I²C capability, by using a 128x32 I²C OLED display, like this one from Adafruit. The one I got doesn’t have the RST and 3.3V pins though, and the PCB doesn’t have mounting holes. I used the ssd1306_128x32_i2c example sketch from the Adafruit SSD1306 library. Adafruit has a tutorial on how to wire the display. Everything worked as expected again.
So this little Pro Mini tryout is done. My impression of the Arduino Pro Mini is that wiring it is more work compared to Arduino Nano. Next I’ll see how to wire the Pro Mini to the digital clock project, and after that try to reduce the current draw.