Raspberry Pi releases PCIe FFC connector specs, new HAT+ commonplace
Raspberry Pi has launched two new specs one for the PCIe FFC connector and associated cable and the opposite for the brand new Raspberry Pi HAT+ (HAT Plus) commonplace that’s easier, takes under consideration new options in Raspberry Pi 4/5, and has fewer guidelines round mechanical dimensions.
PCIe FFC connector specs
The Raspberry Pi 5 was announced over 2 months ago with a new PCIe FFC connector, and people may been playing around with it and even launching products such as an M.2 HAT for the Raspberry Pi 5 since then although the pinout and specs weren’t out there. However Raspberry Pi has now launched the specifications (PDF) for the PCIe FFC discovered within the Raspberry Pi 5 and sure future fashions as properly.
The 16-pin 0.5mm pitch FFC connector incorporates a single lane PCIe interface, one thing we knew already, however the pinout diagram and suggestions for the FFC cable (as much as 50mm in size with managed impedance to 90R+/- 10%) have now been made out there as properly. The PCIe interface is re-confirmed to be PCIe Gen 2 within the specs and the announcement, though Jeff Geerling managed to change settings to allow PCIe Gen 3.
Raspberry Pi HAT+ commonplace
The Hardware on Top (HAT) standard for expansion boards connected on top of the Raspberry Pi SBC was introduced in 2014, and Raspberry Pi simply introduced that the unique HAT specification is now deprecated, and changed with the HAT+ specification (PDF) though that is nonetheless preliminary.
The primary adjustments with the HAT+ specification are:
- HAT+ boards have to be electrically suitable with the STANDBY energy state, the place the 5V energy rail is powered, however the 3.3V rail is unpowered. Notice: Raspberry Pi 4 and Raspberry Pi 5 help the STANDBY state, whereas older Raspberry Pi fashions don’t.
- The specification is much less prescriptive about HAT bodily dimensions.
- The HAT EEPROM content material is now a lot easier.
- A particular class of HAT+s that may be stacked with an additional HAT+ on prime is supported for a most stack of two HATs.
- HAT+ boards are electrically backwards-compatible with older Raspberry Pi fashions, however might have up-to-date software program and firmware to operate accurately.
The primary one could also be necessary to energy consumption in energy off mode. Let me clarify. The Raspberry Pi boards now help two standby modes:
- WARM-STANDBY – The Raspberry Pi is halted/off, however the entire energy rails are nonetheless enabled. That is the default mode when doing a sudo halt or delicate power-button-off operation.
- STANDBY – The Raspberry Pi has the 5V rail powered — so the facility administration chip is powered — however no different energy provides on the PMIC and board are enabled. You’ll be able to configure sudo halt or power-button-off utilizing the EEPROM to enter this mode as a substitute of WARM-STANDBY.
WARM-STANDBY is the default in Raspberry Pi OS so each 5V and three.3V are enabled and that’s why I measured a 1.7W power consumption for the Raspberry Pi 5 when it’s powered off… We will change /boot/config.txt (POWER_OFF_ON_HALT=1, WAKE_ON_GPIO=0) to convey that all the way down to about zero as present in the documentation and tested by Jeff Geerling. So why it’s not enabled by default? That’s as a result of some HATs require each 5V and three.3V. However the brand new HAT+ add-on boards should work with the STANDBY mode at 5V solely.
What does “much less prescriptive HAT dimensions” imply precisely? That’s fairly easy: a HAT+ board solely wants to hook up with the 40-way GPIO header (together with the ID_* pins), and to have at the very least one mechanical mounting gap align with one of many 4 Raspberry Pi mounting holes, and that’s about it which ought to permit for extra type elements. You’re additionally requested to not mess with entry to different connectors and the Raspberry Pi 5 Lively cooler…
One cause the simply launched HAT+ specification remains to be preliminary is that the EEPROM utilities have but to be up to date for the brand new, easier EEPROM parameters. The ultimate model of the specification together with the official M.2 HAT+ board will likely be launched subsequent yr.
Jean-Luc began CNX Software program in 2010 as a part-time endeavor, earlier than quitting his job as a software program engineering supervisor, and beginning to write each day information, and critiques full time later in 2011.