NB IoT Weather Station

WisBlock
#1

Building a weather station on a wisblock that will need to use NB IoT to send its data out.

Will need a I2C interface (temp/humidity), an ADC (wind direction) and at least 2 GPIOs (wind speed interrupt and rain gauge interrupt). Previously using LoRa this worked well with the IO expansion board.

If I plug the NB IoT board on it uses the same slot as the IO expansion - are there enough required pins (listed above) on the Base Board or core I am using (Lora)?

Can IO2 (pin 3 on J11) be used as a GPIO?

Or is there an NB IoT core available?

thanks
Paul

#2

Hi @mutton ,

IO2 is useable as GPIO pin if you are not using it to enable/disable 3V3_S. With that, it seems a WisBlock Base RAK5005-O will be enough: I2C, 1 analog and 2 digital.

Sadly, there is no core with built-in NB-IoT capability and no plan in the future yet.

1 Like
#3

Thanks,

Can I check how you refer to the base board pins in Arduino

IO1 = WB_IO1
IO2 = WB_IO2
AIN = ??? Is it WB_A0 or WB_A1?

WB_A0 is linked to reading VBAT so I hope its not that

#4

Unfortunately it is AIN0 == WB_A0
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#5

Hi @mutton , just to add. You can still use AIN in the header by removing R7 so it will not be connected to the battery.

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#6

Bit of development at last - got it all talking but have realised that IO1 is the BG77 power key so that can’t be used.

So I have decided not to use the wind meter (just rain IO2 interrupt and temp/humidity via I2C) - and would like to reinstate the resistor between AIN0 and VBAT to read the battery level.

What resistor value was R7?

and would it be as simple as me adding a resistor between those two pins (AIN0 and VBAT)?

#7

R7 is a 0 ohm resistor
image

If you connect VBAT directly to AIN0, you will kill the nRF52. VBAT can be between 3.7 and 4.2V, the nRF52 ADC accepts only 3.3V. You might burn the whole MCU.

There is a voltage divider to reduce the voltage on the RAK5005-O

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#8

OK thanks - so I removed R7 and have no way of putting that back on - so how can I make measuring battery voltage work again?

#9

Solder bridge over R7, it is a 0 Ohm resistor, a solder bridge will do.

#10

great thanks, that I can handle