My application does not have access to WiFi or Lora, so I need to use the RAK5860 NB-IoT interface.
With the I/O slot occupied, it rules out using any of the blocks that would allow me to connect to off-board sensors. Hardwiring into the headers isn’t ideal for a lot of users.
My first suggestion is to add Analog inputs to the Sensor slots on the baseboard (I can’t believe that they are not there already) Eg on Slot B and Slot D of the RAK5005, connect AIN1 to Pin 1 and AIN2 to Pin 24
Next, create a couple of modules in the Sensor form factor with a single Grove type connector, eg
Serial: RXD1, TXD1, VCC, GND (protected against 5V serial signals)
Analog: AIN1, AIN2, VCC, GND (analog signals divided from 0-5V input and buffered)
I2C: SCL, SDA, VCC, GND
(if you would rather not use Grove connectors due to commercial factors, a 2.54mm molex header would be a generic alternative)
Ideally, I would love if a switched 5V VCC was available such as in the RAK5811 but if room wasn’t available in the sensor form factor, 3V3_S would suffice.
Better again would be to give a choice of both voltages with a P-type mosfet connected from 3V3_S to the output of a 5V boost and the gate of the mosfet connected to the boost enable line. With 3V3_S switched on and the enable off, you could select a 3.3V VCC. Turning on the enable would boost the 3V3_S to 5V and turn off the mosfet.
Congratulations on building a superb system, I’d love to see it expand,