The MSP430 family by Texas Instruments consists of low-cost, low power 16 bit processors. For the charge controller the sub 1 USD parts with included analog to digital converter are the most interesting ones.

Here's a list of suitable parts:

At the moment, the following peripherals are important for the project:

  • 10 bit SAR ADC: measure voltages and currents to determine the state of the rechargeable battery and the solar panel
  • Capacitive touch I/O: features which allow easy programming of a capacitive proximity sensor. The sensor will be used as the on/off switch for the device.
  • Enough RAM and Flash memory: since the software isn't completed yet, the exact required amount of flash memory and RAM is unknown at the moment
  • DIP packaging: for easy assembly, the microcontroller is available in a DIP package

For programming these parts, the MSP430 LauchPad Value Line programming system is available for <5 USD: