Its 40-pin GPIO connector has certainly contributed to the popularity of the Raspberry Pi, making it very easy to extend the basic board with custom modules. Did you know these lines are connected directly to the CPU? This makes them fairly vulnerable. Have you noticed there is hardly any hardware support for generating PWM signals (only one PWM pin is available)? And there are also no analog (ADC) inputs.
The Swiss Pi HAT eliminates these short­comings and provides a number of extra features, including a real-time clock and an RS-485 interface.
 

Ready assembled module available
Full description published in Elektor Magazine in issue 9/2016 on page 44.
 
  • Features
    •  16 GPIO lines with configurable pull-up, 5-V signal levels
    •  16 12-bit PWM channels, configurable 24–1526 Hz, 5-V signal levels
    •  4 connectors for remote control servos (shared with PWM channels 0 to 3) and supply voltage connector
    •  8 12-bit ADC inputs, range 0–4.096 V
    •  Half-duplex RS-485 interface compliant with TIA/EIA 485A standard, with ESD protection
    •  Precise real time clock with battery backup, 3 ppm accuracy
    •  I2C extension connector, 5-V signal levels
    • ID EEPROM