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A CHEAP SOLAR POWERED STM32 ARDUINO NODE

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ABOUT THIS STORY


Posted on March 11, 2017



Intermediate
2 Hours

Introduction


After building a cheap Atmega32 Arduino node as described in this story:
https://www.thethingsnetwork.org/labs/story/build-the-cheapest-possible-node-yourself

I decided to build a similar node based on the STM32F103C8T6 boards you can buy on Ebay and other sources for about $ 2.00.

See e.g.
https://developer.mbed.org/users/hudakz/code/STM32F103C8T6_Hello/
for a board description.

The main advantages are:

  • Much more space for your program (most boards have 128K flash even when advertised as 64K)
  • 20K RAM
  • High speed 32 bit ARM Cortex-M3 processor up to 72Mhz

The main disadvantages are higher power usage and a slightly larger board, but you can switch to lower speeds (8Mhz) and activate sleep modes to safe power when running on a battery or solar panel.

It will use only 70μA while sleeping if you remove the power led and 12μA without the regulator.