Design 3.3v compatible version

[ruifig]

The old version used some components that were not compatible with 3.3v logic/voltage, such as the L293D to control the motors. A new design is needed that can be used with 3.3v, and potentially also usable with 5v with minor changes.

Things I can think of that should be done as part of this task:

• [x] Design new version with Fritzing

Confirm the new design is probably ok by testing various things with temporary code

• [x] I2C in general seems ok ?
• [x] Display
• [x] Touch
• [x] Soil moisture sensor reading
• [x] Temperature and humidity sensor reading

[ruifig]

New design doesn't seem to have any problems with 3.3v so far.