I've recently bought an RN4020 BLE module, but I'm having figuring out how to make it work. In the datasheet some pins are listed as 1.65V input, 1.35V out, while for the rest of them, there's no indication whatsoever. How can I figure out what voltage levels the pins specifically the TX, RX, WAKE_SW and WAKE_HW use?
Electronic – What are the UART voltage levels for the RN4020
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Best Answer
While it's not explicitly mentioned in the datasheet the typical application schematic seems to indicate it is compatible with 3.3 V logic because the following nets are connected directly to the RN4020 module, although you wouldn't want to exceed the Vdd supplied to the module which is 3.3 V in this case as well:
The I/O pins you've mentioned also include analog I/O so are probably connected directly to an internal ARM processor running at around 1.6 V. I've seen that configuration on other wireless modules before and the minimum supply voltage of 1.8 V would seem pretty much in line with it having an internal low-dropout regulator.
The datasheet is marked as "advance information" so while I think powering the whole system from 3.3 V as per the application schematic should be safe enough if that isn't suitable for your particular application it may be worth enquiring further with Microchip.