RAK19003/19007 Power supply over Solar port

WisBlock
1

Hey, I’m currently designing a device that contains a Pi Zero 2W and a node with either a RAK19003 + RAK4631 or a RAK19007 + RAK4631. To extend the battery life, and as the RAK requires 3.3V but the Pi runs on 5V, I’m thinking of using a Waveshare solar charge controller module.
This unit will manage the inputs (USB-C, solar cell integrated into the casing + external cell), as well as distributing power to the two devices (through the same splitted 5V/3A output) and charging the battery (3 x 18650GA, 3.7V 3300mAh).
The two devices (RAK Node and Pi Zero) will be connected to the same earth (GND).

With this in mind, I was wondering whether it is possible to power the RAK19003/19007 through the solar port on the rak 19003/19007 from the power manager, so as to keep the USB port on the RAK baseboard free?

2

Welcome to the forum @KentBrock

Yes, you can supply the Base Boards with 5V DC through the solar panel connector.
You can use the USB port in parallel without problems.

3

Hi Bernd, thanks for your reply!
I’m still a bit unsure about the grounding of the two devices (RAK and Pi). Can I connect the UART port GND (J7) on the RAK19003 to a GPIO GND pin on the Pi? And will there be a conflict if I use the RAK’s USB-C port to connect to the Pi’s OTG port for data?
Alternatively, I was thinking of connecting the RAK and the Pi entirely via the UART on the RAK side (J7, GND, TX, RX) and the GPIO GND, RX and TX pins on the Pi, but what happens with the grounding when one device is off?

4

You have to connect the GND’s of the WisBlock and the RPi if you connect the two through the UART. If not connected, the two might be on a different GND level and this would lead to problems. If one device is off, it doesn’t matter.