Recently the Raspberry Pi Foundation released the latest and greatest Raspberry Pi – the Raspberry Pi 4. Aside from being the most powerful Raspberry Pi, there was one major hardware change that caused it to break compatibility with all the other previous Raspberry Pi’s and that was changing the power connector from a Micro USB B connector to a USB-C connector. One reason for this was that the Micro B had been running out of steam with every new generation of Raspberry Pi’s demanding more and more power. Finally with the Raspberry Pi 4, they needed a connector capable of supplying more power and hence the jump to the USB-C connector.
Compatibility with Sleepy Pi 2
Is the Sleepy Pi 2 compatible with the Raspberry Pi 4? Yes…and…No…partially.
Now remembering that you can supply power either from a high voltage up to 30V OR a 5 V input :
The “Yes” is that if you supply power via the 5.5 – 30V External Power then that’s all good.
However, the “No” is the Micro B USB connector. It just drops too much voltage over the cable and connector, that by the time it gets to the Raspberry PI 4, it’s right on the ragged edge and not recommended.
The “Partially” is that if you pipe the 5V directly into the Sleepy Pi 2 via the solder pads – shown as “5V Power Input” in the picture above, then it’s OK. Though I would recommend (if you can) setting the 5V to the top of the 5V spec of 5.25V to give a bit of headroom.
So, basically, if you supply power via either the External Power or 5V Power Input’s shown in the image, you’re OK.