NXP app note with diagram and explanation is here:
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On Sat, Jan 18, 2020 at 12:42 PM, Joerg ex-DB2OO wrote:
I used an I2C level shifter module with 4 level shifters, which I purchased on eBay (approx EUR 1.95).
This does a conversion between the low and the high voltage in a bi-direction way:
For the 5th signal I simply used a resistor voltage divider with 560Ohm connected to the Nano output (5V) and 1kOhm connected to ground.
The midlle of the divider is connected to the SI4432 input.
Generally you can use these voltage dividers for all outputs of the Nano.
This will leave just one signal, that needs a 3.3V --> 5V conversion, which requires e.g. a level converter as shown above. Not using an up-level converter might work, but the input level at the 5V Arduino will be out of spec.
There are other ways for level conversion like shown here:?.
Overall my prototype TinySA with an Arduino Nano looks like this:
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Joerg, ex-DB2OO
