HC-05 module on a JY-MCU breakout board - what and how is it buffered ?

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Hello all,

I've bought myself a HC-05 module on a JY-MCU breakout board, but cannot  
seem to find anything concrete about what the JY-MCU breakout board (stamped  
ZS-040) does or needs.

The pinning:

STATE (out)
RXD \ 3.3v
TXD  /
GND \ 3.6 ... 6v
VCC /
EN (in)

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 ?

Secondary problem: What is the EN pin connected to on the HC-05 module ?  
What is it supposed to do ?

And some confusion: Why does the JY-MCU board have a voltage regulator at  
all ? Now it can't connect to a pure 3.3v MCU, and when used with a 5v MCU  
it needs logic-level conversion buffers for the communication.  That doesn't  
makee much sense ...

Regards,
Rudy Wieser



Re: HC-05 module on a JY-MCU breakout board - what and how is it buffered ?
declaimed the following:

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    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.


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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???



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

Re: HC-05 module on a JY-MCU breakout board - what and how is it buffered ?
Dennis,

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I would think so too, but I've found descriptions using different, but  
rather similar break-out boards, with some of those descriptions  
specifically mentioning 3.3v for the KEY pin, and using a resistor divider  
to drop the 5v signal to a 3v one for the RXD pin.

But the below tutorial directly connects the KEY and RXD input pins to the  
Arduinos output pins (supposedly being driven at 5v).

https://www.instructables.com/id/How-to-Set-AT-Command-Mode-for-HC-05-Bluetooth-Mod/

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:-) I found the same PDF.   And if the HC-05 module would be all that I had  
(not on a break-out board) my problems, other than how to attach wires to  
it, would not exist.

The whole thing is that I do not know what the JY-MCU breakout-board the  
HC-05 module is placed ontop of does for me.    Having discovered that  
multiple *unspecified* versions of that breakout-board circulate doesn't  
help either. :-(

On my JY-MCU break-out board I can see 6 (assumed to be) resistors, one LED,  
one three-legged component that I assume is the voltage regulator, and  
another three-legger which I haven't got the foggiest about (perhaps a  
transistor or FET driving the LED ?).

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Have you looked at that breakout-board image just above it ?    It doesn't  
seem to have /any/ components on the break-out board itself ...    Either  
all of them are on the other, bottom side or this shown module isn't quite  
representative.

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:-D Yep, I found similar.    Which one of the two should I believe ?

Ofcourse, its easy enough to test for my particular module (just send an  
"AT",CR,LF and see what comes back), but that should /not/ be needed. :-(

(its possible that the above-mentioned three-legger is a transistor or FET  
allowing the EN pin signal to rise above 3.3v - but inverting that signal in  
the process)

And I see we are bumping against the same inconclusive information. :-)
No matter, thanks for the response.

Regards,
Rudy Wieser



Re: HC-05 module on a JY-MCU breakout board - what and how is it buffered ?
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Some 3.3v logic interfaces are 5v tolerant. You need to see the  
device datasheet for that. Often a resistor (I've seen 1Kohm mentioned)
directly in the signal line is enough to prevent damage. AFAIK it uses  
the, often, inbuilt powerline protection diodes - but I'm sure a more  
comtetant HW guy could spell chapter and verse.

I think there was a discussion on this NG earlier this year about  
interfacing 5v to the Pi - utilising a 1K resistor for protection - or  
maybe it was anoth NG or Forum.



Re: HC-05 module on a JY-MCU breakout board - what and how is it buffered ?
Jim,

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The question is: Should I bother to check the HC-05 datasheets, or does the  
JY-MCU breakout board already handle it (which I thought it was there for) ?

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Yes, I'm aware of that possibility.

The thing is that currently I cannot find *any* information on what the  
JY-MCU breakout board does or doesn't do (like does it already have such a  
series resistor in place ?) - or even what its STATE and EN pins are  
supposed to be there for. Which is the whole problem.

And yes, I could spend some time trying to trace some of the tracks on the  
breakoutboard to the components on it (by eye or ohm meter) and than do /my  
best guess/* to what is going on, but that is definitily NOT the way it  
should be going.

*and hope that its good enough!.

Currently I feel like I've been had, as if I've bought myself a cheap  
throw-away gadget. :-(

Regards,
Rudy Wieser  



Re: HC-05 module on a JY-MCU breakout board - what and how is it buffered ?
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https://www.moore-duino.co.uk/product/hc05-hc-05-bluetooth-serial-module-breakout-board-jy-mcu/

STATE Mode the device is in           from a photo is seems to imply
                                      this is an output from the device
                                      indicating the state
RXD         Receive
TXD         Transmit
GND         0V
VCC         5V
EN         Disables module when LOW   this is fairly explicit.  
                                      Pull low to disable the module
                                    


The photo shows RX/TX at 3.3V logic levels. Even it has a safety  
resistor putting another one will very probalby be ok - and safe!
Or buy a little dual 3.3V <-> 5V level shifter to use between the  
device and the MCU. If you are interfacing to the RPI then all is ok as  
they are 3.3V logic. (this is the RPI NG!).



Re: HC-05 module on a JY-MCU breakout board - what and how is it buffered ?
Jim,

Thanks for the link.  But look at that pin <-> description table.   It  
doesn't actually *say* anything.

"STATE" "Mode the device is in"

- What "mode" are they talking about ?
- Which pin of the HC-05 module is it connected to ?  (presuming it is)
- Is it a direct connection or does the break-out board have any components  
(resistor, diode, etc) in it.  If the latter, for what purpose (what is its  
effect).
- In the case its /not/ a direct connection : Which "high" voltage does it  
output ?

"EN" "Disables module when LOW"

- Which pin of the HC-05 module is it connected to ?  (presuming it is)
- Is it a direct connection or does the break-out board have any components  
(resistor, diode, etc) in it. If the latter, for what purpose (what is its  
effect).
- In the case its /not/ a direct connection : Which "high" voltage does it  
accept (min and max) ?

You know, the basic stuff.

Really, just mentioning where the STATE and EN pins are connected to on the  
HC-05 module would be, to me, way more helpfull.

Furthermore:
- if a low disables the module, how to I enter the "command" mode (so I can  
configure it), as my module doesn't have a pushbutton.  ... or did I buy an  
intentionally crippled one ?    That would be a bit hard to swallow.

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You mean by way of the silk-screen text ?   Yeah, I noticed.

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Don't be too sure about that: back-current thru such a resistor and the  
clamping diodes is known to be problematic (I probably followed the same  
thread you mentioned :-) )

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Yeah, I know I can do that.  Together with another 3.3v voltage regulator  
(and supporting components) ofcourse.  But thats sheer insanity.

Bottom line: A breakout board which makes it impossible to feed the HC-05  
from a 3.3v source (presumably due to a voltage drop in the power  
regulator), but which also doesn't seem to have anything for the signal  
lines to make it easy to use the HC-05 module on a higher voltage.   Its  
almost as if its some kind of intricate joke.

Regards,
Rudy Wieser  



Re: HC-05 module on a JY-MCU breakout board - what and how is it buffered ?
I'd say there's enough info to get you going - at least for HW.
Perhaps you didn't do sufficient research before you  bought?

Good luck
Jim
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Re: HC-05 module on a JY-MCU breakout board - what and how is it buffered ?
Jim,

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And as I've already tried to make clear, I absolutily disagree with you  
there.

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True.  With the meager information the webshops page offered I assumed that  
the rest of it would be provided with the module itself.   Thats not a  
mistake I will easily repeat.

But tell me, as the breakout board itself does not have much, if anything,  
to descern it from a multitude of other boards (all sold under the generic  
HC-05 breakout board name) how would I find the information to it ?  What  
would I need to search for ?

And as you might have noticed, I did such research - just afterwards instead  
of beforehand - only to discover that none is to be had (or to be more  
precise: enough "user generated content" floating around, but at times  
conflicting with each other - making it inconclusive)

Which is why I asked here.


Bottom line: Even though I bought a breakout-board module enabeling the  
HC-05 module to work with supply voltages between 3.6v and 6v it can't be  
used (connected) in any way (to a 3.3v or a 5v MCU) without adding more  
components*.  Which is not what I expect from a "use with different supply  
voltages" breakout board.

*with the RPi as an exception, as it has 3.3v signal lines and a 5v power  
output pin.

Regards,
Rudy Wieser



Re: HC-05 module on a JY-MCU breakout board - what and how is it buffered ?
declaimed the following:

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    The odds are very good that all pins on the module map directly to the
same pin of the HC-05 chip itself... And most likely the chip specification
sheet will use the same name.

    Now -- if they are buffered/inverted between the module pins and chip
should be in the documentation from the module manufacturer. If there is no
such documentation, or only a reference to the chip specification, it is up
to you to determine what is happening or contact the module manufacturer.
(Let me guess, you went lowest bid on eBay for this)

https://www.instructables.com/id/Success-Using-the-JY-MCU-linvor-Bluetooth-Module/
https://www.tautvidas.com/blog/2015/12/easy-arduino-bluetooth-communication-with-jy-mcu/
(Note: this particular variant indicates the "Key" [EN] pin is used to
update the on-board firmware and not to toggle into AT command mode --
might be a difference between HC-06 and HC-05 chips; feel free to search
for spec sheets of the two for comparison)

https://www.instructables.com/community/Are-the-JY-MCU-and-the-HC-05-bluetooth-module-the-/
implies the module has voltage converters for 5V I/O.

https://www.amazon.com/Master-Slave-Anti-Reverse-Integrated-Bluetooth-Pass-Through/dp/B07JFYSZR6#detail-bullets
The schematic diagram shows a Maxim MAX3232 chip -- but it appears that
chip is unused unless you wire up to some of the pads on the module. The
MAX3232 is used to translate TTL UART signals to real RS232 (+/- 12V). {The
J1 connector has both TTL level and RS232 level -- but that is on an 8-pin
connector, but the module only exposes a 6-pin connector} There is a
transistor cascade taking "UART TXD" and boosting it up to 5V "TX TTL"
level. "RX TTL" appears to just be fed to through a diode to drop the
signal to 3.3V "UART RXD". Note that both of those conflict with the bottom
labeling on this module, which states 3.3V levels for RXD and TXD.

    At this point, I'd probably pull out an oscilloscope and put that on
the output pin&ground, then apply first 3.3V to the module, followed by 5V
-- and seeing what voltage peak appears on the output (the schematic
implies the output has a 5V pull-up, so I'd guess that is the default level
for the output, and the transistors are used to draw it down to GND level).


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

Re: HC-05 module on a JY-MCU breakout board - what and how is it buffered ?
Dennis,

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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%20Datasheet.pdf

No EN or STATUS pins.  Heck, not even RXD and TXD are present as such. :-)

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That is documentation I expected to come with the module, but didn't.   And  
with the absense of an actual product number (other than the webstores  
internal one) there is no way to get at it.

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Nope.   I ordered it thru a webshop in my own (small) country.  Pretty-much  
to forgo the kind of horror stories you sometimes read about ordering  
abroad.  Alas, It looks like I fell into another pit.

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That would clash with the "LEVEL : 3.3V" silk-screen info on the back of my  
module (directly next to the RXD and TXD pins) - which makes me yearn for  
the breakout boards manufacturer specs.

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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)

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Yup.  Conflicting/mismatching info that I've also found during my searches.  
Which either means someone (a hobbyist ?) cut corners, or is possibly  
targetting a different module ...

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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. :-)

Though its definitily /not/ something I expected to need to do.   I will  
probably refrain from buying more, as I would likely need to go thru the  
whole song-and-dance again. :-(

Regards,
Rudy Wieser



Re: HC-05 module on a JY-MCU breakout board - what and how is it buffered ?
declaimed the following:

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    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-Firmwa/
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).
"""

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    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

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    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
     snipped-for-privacy@ix.netcom.com    http://wlfraed.microdiversity.freeddns.org/

Re: HC-05 module on a JY-MCU breakout board - what and how is it buffered ?
Dennis,

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...

I'm sorry, but I ment that I actually looked at the contents of that PDF  
(read: it opens fine), and found that the names for the pins on the breakout  
board do not match any names in that PDF document (though I went a bit of a  
stretch for the RXD and TXD pins - those are rather easy to find the similar  
names for :-) ).

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I found a webpage describing that process for a button-less module.  I saved  
it for a "just in case" case.  And whatdoyouknow, it has become just that.

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Not quite.  It could as easily be connected to the RESETB pin (pin 11).

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Indeed.   Especially the USB pins, and asked myself if I could perhaps wire  
it up to an USB connector - only to realise that if the firmware is not  
written for it neither the SPI nor the USB pins will do anything.   Heck,  
those hardware parts might not even be on the used chip.

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Although I would gladly accept that (would make my life /that/ much easier),  
its not what the specs to the HC-05 breakout board says : a 3.6v minimum  
voltage.   But, I don't know why they say that*, as the HC-05 module itself  
will, according to the PDF, happily work with a supply as low as 1.8 volts  
...

*other than perhaps to guarantee that the I/O "high" level is at 3.3v.

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The breakout board has some space for that button, but its not present.  
With some luck the track is connected to that pin though, allowing me to put  
a makeshift switch there myself.

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Could you post the direct link to that image ?

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Thats something that crossed my mind too ...  Though I got very little  
choice if I want to check where the STATE pin connects to.

Thanks for the help - again. :-)

Regards,
Rudy Wieser



Re: HC-05 module on a JY-MCU breakout board - what and how is it buffered ?
declaimed the following:

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    Based upon the link that suggested uploading a more capable firmware, I
suspect the chip does have all the parts for that pinout. The SPI pins
appear to be used for firmware updating.

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    Partly, I suspect, as any on-board voltage regulator will consume some
of the input voltage just to ensure a stable 3.3V output. The second reason
may be that MAX3232 (or was that 2323 <G>). The double ended voltage
multiplier (to get both +12 and -12 for true RS-232) may require at least
some higher level to function.

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    I'd like to, but the image selection appears to be handled by Amazon
Javascript on the page, as the mouse passes over them -- the URL doesn't
change. I see, on the left:

Top view diagonal of board with jumper at lower right,  with small
schematic bottom left and module dimension diagram top right.

Diagonal view top with jumper at lower left, no auxiliary diagrams

Top down view, jumper on left

Diagonal view bottom, jumper lower right

Schematic only

Module dimensions only


    The page source is over 18000 lines (about half are blank lines), most
is Javascript. The thumbnail for the image is at line 9720, but I don't
know how to go from
https://images-na.ssl-images-amazon.com/images/I/41fnAp8oUUL._SX38_SY50_CR,0,0,38,50_.jpg
to the full size version. I suspect it's coded into that file name, and the
server parses it to provide the image as the mouse moves over the
thumbnail.


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

Re: HC-05 module on a JY-MCU breakout board - what and how is it buffered ?
Dennis,

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Yes.  0.3 volts.  At least, thats the difference between the minimum allowed  
supplied and the I/O voltage.   Supplying 3.3v should drop the I/O voltage  
to 3.0 volt, which should be plenty enough for an input pin of a 3.3v MCU*.

That is, assuming that the voltage regulator itself doesn't throw a wrench  
into it (will go into  a kind of "pass thru" mode when it gets a too-low  
voltage).

*on the other hand, having an output pin supply 3.3 to an input-pin of  
device that runs on 3.0 volts could create problems in regard to possible  
present clamping diodes.

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My thanks for going thu it.   Thats really a cr*pload.

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I took a chance and just removed everything from the second-to-last dot upto  
the ".jpg" extension.   I got a 500x500 image back, which stil is isn't  
perfect but better readable than what I had.

Regards,
Rudy Wieser



Re: HC-05 module on a JY-MCU breakout board - what and how is it buffered ?
On Tue, 14 Jul 2020 19:27:08 +0200, R.Wieser wrote:

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1st result when searching for hc05 on google
https://components101.com/wireless/hc-05-bluetooth-module
seems pretty straight forward to me




--  
I know on which side my bread is buttered.
        -- John Heywood

Re: HC-05 module on a JY-MCU breakout board - what and how is it buffered ?
Alister,

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Absolutily !

.... up until the moment you find some more of the same on other webpages,  
which mentions that the EN pin just disables the module.  No mentioning of a  
datamode there.

Also, my board doesn't have that button shown there.  Should I therefore  
presume its crippeled ?  Or does it maybe work differently ?

And by the way: No mentioning of signal levels for/of the EN and STATE pins  
anywhere, nor if the breakout board adds tolerance for 5v signals on TX and  
RX and perhaps the above two too.

To make things worse: the wiring diagram in the "How to Use the HC-05  
Bluetooth module" chapter mentions that the TXD and RXD go to the MCU -  
which under the "HC-05 Technical Specifications" might be an Arduino - which  
is supposed to run on 5v, and directly connecting the RX pin to one of the  
Arduinos pins set to output will likely destroy the 3.3v module.    Either  
someone forgot something, or that particular module can handle 5v signals.

Nope sirree, its not as straight forward as you think it is. :-)

Regards,
Rudy Wieser



Re: HC-05 module on a JY-MCU breakout board - what and how is it buffered ?
On Thu, 16 Jul 2020 22:05:22 +0200, R.Wieser wrote:

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Tx & RX are described as TTL serial
TTL is a fully detailed standard as far as signal levels go.
  



--  
If I had a Q-TIP, I could prevent th' collapse of NEGOTIATIONS!!

Re: HC-05 module on a JY-MCU breakout board - what and how is it buffered ?
Alister,

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Your second mistake.

Just take a look here:

https://www.sparkfun.com/tutorials/215

"Serial communication at a TTL level will always remain between the limits  
of 0V and Vcc, which is often 5V or 3.3V"

Nowerdays a "TTL signal" often doesn't refer to the voltage, but to the  
"low"/"zero" level being at 0v, and the "high"/"one" level being at VCC  
(regardles of what VCC might be) - as opposed to an RS232 specced signal,  
where "low" is at +v and "zero" at -v.


And I see that you did not read my initial message too closely.   In it I  
wrote that the RXD and TXD pins are specced as having 3.3v levels ...

Regards,
Rudy Wieser



Re: HC-05 module on a JY-MCU breakout board - what and how is it buffered ?
On 17/07/2020 14:07, R.Wieser wrote:
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FWIW there is somewhere the original TTL spec where 0 is less than some  
voltage and 1 is more than some voltage with in between being 'here be  
dragons'

"A TTL input signal is defined as "low" when between 0 V and 0.8 V with  
respect to the ground terminal, and "high" when between 2 V and VCC (5 V)"

Whether or not what you are discussing conforms to that, I do not know.  
Just my 2 pennoth..

--  
?It is dangerous to be right in matters on which the established  
authorities are wrong.?

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