On Tue, 14 Jul 2020 19:27:08 +0200, "R.Wieser" 
declaimed the following:

>Biggest problem: The voltages (in and out) of the EN and STATE pins.   Are
>they 5v tolerant or is 3.3v the maximum for either (signal voltage or
>pull-up).   And are the RXD and TXD pins 5v tolerant ?
>

 The first description I find for the HC-05 (ignoring the actual module
maker) mentions "Arduino" -- and I suspect they mean Uno, Mega, or other
AVR Arduino, rather than one of the ARM based ones.

 If so, the board is optimized for 5V signals (though that page says
4-6V for VCC).

 A datasheet for the chip itself says 3.3V VCC
http://www.electronicaestudio.com/docs/istd016A.pdf

 This page
https://maker.pro/custom/tutorial/hc-05-bluetooth-transceiver-module-datasheet-
highlights
states all are 3.3V except for VCC. And if the unit has on-board regulator,
there is typically some losses involved, so one needs 4+V to get 3.3V out.


>Secondary problem: What is the EN pin connected to on the HC-05 module ?
>What is it supposed to do ?
>
https://components101.com/wireless/hc-05-bluetooth-module
"""
This pin is used to toggle between Data Mode (set low) and AT command mode
(set high). By default it is in Data mode
"""
Though the tutorial link states that EN pulled LOW during power-up is
needed to enter command mode???



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 Wulfraed                 Dennis Lee Bieber         AF6VN
 wlfraed@ix.netcom.com    http://wlfraed.microdiversity.freeddns.org/

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