Raspberry Pi has introduced two new standards: the PCIe FFC connector specifications and the Raspberry Pi HAT+ (Hardware on Top Plus) standard. These are designed to enhance compatibility and functionality with the newer Raspberry Pi models, specifically the Raspberry Pi 4 and 5.

PCIe FFC Connector Specifications:

• This new connector was first seen on the Raspberry Pi 5, introduced over two months ago. The 16-pin 0.5mm pitch FFC connector offers a single-lane PCIe interface.
• The pinout and recommendations for the FFC cable (up to 50mm in length with a controlled impedance of 90R±10%) have been made available. The interface is confirmed as PCIe Gen 2, though some have managed to enable PCIe Gen 3.

Raspberry Pi HAT+ Standard:

• This new standard replaces the original HAT specification from 2014, with several key changes:
  • HAT+ boards must be electrically compatible with the STANDBY power state (5V powered, 3.3V unpowered), which is supported by the Raspberry Pi 4 and 5.
  • Less restrictive physical dimensions for HAT+ boards.
  • Simplified EEPROM content for HAT+ boards.
  • Support for stacking up to two HAT+ boards.
  • Electrical backward compatibility with older Raspberry Pi models, though updated software and firmware might be required.

HAT Dimensions:

• HAT+ boards need only connect to the 40-way GPIO header and align with one of the Raspberry Pi's mounting holes, allowing for more diverse form factors.

M.2 HAT+ for Raspberry Pi 5:

• A prototype M.2 HAT+ for Raspberry Pi 5 is in development, with considerations for not blocking MIPI connectors.
• The final version of the HAT+ specification and the official M.2 HAT+ board are expected next year, pending updates to the EEPROM utilities for simpler parameters.