On Thu, 16 Jul 2020 12:11:09 +0200, "R.Wieser" 
declaimed the following:

>No such luck I'm afraid.   I'm looking at the HC-05 datasheet here :
>
>https://components101.com/sites/default/files/component_datasheet/HC-05%20Data
sheet.pdf
>
>No EN or STATUS pins.  Heck, not even RXD and TXD are present as such. :-)
>
 Unfortunately, that PDF uses images, and not formatted text -- so no
cut&paste...

 Page 4 lists: UART RTS, UART CTS, UART TX, and UART RX

 Page 5 states
"""
How to set the mode to server (master):
1. Connect PIO11 to high level.
2. Power on, module into command state.
3. Using baud rate 38400, sent the “AT+ROLE=1\r\n” to module, with
“OK\r\n”
means setting successes.
4. Connect the PIO11 to low level, repower the module, the module work as
server (master).
"""
which does seem to follow what one document implied for the EN pin -- used
to enter command mode rather than data mode.

 Note that the actual chip has a lot of pins, many used for esoteric
reasons (PIO pins imply their use depends upon the firmware on the chip --
https://www.instructables.com/id/Upgrade-Your-3-Bluetooth-Module-to-Have-HID-Fi
rmwa/
ties into the SPI pins for programming the chip).

https://athena-robots.readthedocs.io/en/latest/hc05_bluetooth.html also
echoes the PIO11 information:
"""
Among all the available pins, the HC-05 firmware uses the following pins in
a minimum system:

    UART_TXD and UART_RXD for serial transmission (communication with the
microcontroller).

    PIO8 usually connects with a LED. When the module is power on, LED will
flicker. And the flicker style will indicate which work mode is in since
different modes have different flicker patrons. It will blink fast in
pairing mode, slow in AT mode and fill double-blink each couple of seconds
after paired with another device
.
    PIO9 also is usually connected with a LED. It indicates whether the
connection is built or not. When the Bluetooth serial is paired, the LED
will be turned on. It means the connection is built successfully.

    PIO11 is the work mode switch. When this PIN port is input high level,
the work mode will become order-response work mode (AT mode). While this
PIN port is input low level or suspended in air (high impedance), the work
mode will become automatic connection work mode.

    PIO0 and PIO1 to enable RX and TX lines.

    RESET, VCC and GND for obvious purposes.
"""

 STATUS is likely PIO8, though could be PIO9 (or even going through an
AND or OR gate of the two)

"""
Many times the HC-05 comes already mounted on a PCB in a very reduced
working system, just enough to use the serial communication. Note that:

    Although many of these mounted devices are compatible with 5 V logic
levels, they do work just fine with 3.3 V.

    Some may have a small switch connected to pin 34. This is very
convenient, as we can very easily enter AT-mode this way (just press the
switch while you power on the device).
"""

>
>I'm afraid that that schematic (in the same image as the module) is just a
>tad too blurred to be able to read any text there.   Heck, can't even see
>what the two words at either end of that diode say (and I've even scaled up
>the 1000x1000 "hires" image to try)
>
 The fifth image down on the Amazon page (at least for me) is just the
schematic at a somewhat larger scale. The diode part is

 UART_RXD --->|--- RX_TTL

>
>I was thinking of using an ohm meter to figure out where the breakout board
>pins lead to (directly connected to the HC05 module or thru something), but
>your idea doesn't sound half bad either. :-)
>
 If using an active ohm/resistance measuring mode, I'd be concerned.
DVMs tend to run 6-9V (4xAA, 1x9V) through the leads when measuring
resistance. That could fry a 3.3V CMOS system. The o'scope is high
impedance and passive, not injecting any voltage on the pins.


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

--- SoupGate-Win32 v1.05