Arduino Pro Mini, 3.3V and JY-MCU bluetooth

Using Arduino Project Guidance
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Hi guys

I´m very new to Arduino, and I hope you can help me a bit.

I have just bought the Arduino Pro Mini, 3.3 V and JY-MCU bluetooth module from Ebay.

I´m not sure if the bluetooth board is working correctly, after connecting it with an Arduino Pro Mini 3.3V, the LED does not light and I cant find the board either on my pc or phone.

I have connected:
GND to GND
VCC to VCC,
TXD to RXI and
RXD to TX0.

I have powered the Arduino with 3 volts through VCC and GND.
Is this connected in the right way?

I should be able to see the BT module as a device on my computer or phone without uploading any code to the Arduino, right?
I know that my Pro Mini works, since I did the blink sketchs, and it worked fine.

Best regards Kasper

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Kapper86:
TXD to RXI and
RXD to TX0.

I have powered the Arduino with 3 volts through VCC and GND.
Is this connected in the right way?

It first guess, the answer is almost certainly "no". The JY-MCU is clearly marked 3.6 - 6 volts. It's written on the back, right where you are supposed to see it. Clearly, running it off 3.3 volts means you are about 10% short, and that can't possibly be a good idea. Having said that, there is a recent thread run by Heartfelt-Angel, who is doing the same thing and getting away with it. That doesn't make it any smarter, and doesn't mean that you will, but you might, although I suspect you haven't.

Your connections read wrong too.

Tx > Rx
Rx > Tx

What you have implies mixing ports.

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Hi Nick

Thank you for your quick reply.

On the Arduino Pro Mini, there are no ports marked as Tx or Rx, only RXI and TX0, so I guess I have connected them correct?
I understand what you mean about the power. My Arduino is running 3.3 v, so I´m afraid to put more voltage than that. Can i supply 4.5v to the Raw input on the Arduino, and wire the Raw to the bluetooth, so the bluetooth would get 4.5v as well?

I followed this guide: http://robotosh.blogspot.nl/2012/07/arduino-jy-mcu-bluetooth.html - I uploaded the code, but I still cant see the bluetooth device on the pc, and the LED does not blink.

Kasper

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Summary

Microcontroller ATmega168
Operating Voltage 3.3V or 5V (depending on model)
Input Voltage 3.35 -12 V (3.3V model) or 5 - 12 V (5V model)
Digital I/O Pins 14 (of which 6 provide PWM output)
Analog Input Pins 8
DC Current per I/O Pin 40 mA
Flash Memory 16 KB (of which 2 KB used by bootloader)
SRAM 1 KB
EEPROM 512 bytes
Clock Speed 8 MHz (3.3V model) or 16 MHz (5V model)

Use a 5V regulator to power both. A standard 5V regulator circuit should suffice, also make sure you have the correct capacitors too.

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Kapper86:
On the Arduino Pro Mini, there are no ports marked as Tx or Rx, only RXI and TX0, so I guess I have connected them correct?

OK I think it was just a case of me misreading you - and the way it is printed on your Arduino. So long as you are sure. Quite apart from that, I think in the rest of Arduinoland pin 0 is Rx and Pin 1 is Tx'

I understand what you mean about the power. My Arduino is running 3.3 v, so I´m afraid to put more voltage than that. Can i supply 4.5v to the Raw input on the Arduino, and wire the Raw to the bluetooth, so the bluetooth would get 4.5v as well?

I can't really comment but it appears your Arduino has on-board regulators - hence RAW, so your proposal sounds about right - probably a lot more right than running Bluetooth on 3.3v.

still cant see the bluetooth device on the pc, and the LED does not blink.

These background notes might help,

http://homepages.ihug.com.au/~npyner/Arduino/GUIDE_2BT.pdf
http://homepages.ihug.com.au/~npyner/Arduino/BT_2_WAY.ino

but fix the power and check the wiring - again. I assume by "does not blink", you see nothing. This suggests improper power supply.

I have just had a look at that blogspot and I'm not impressed. The stuff about the LED is confusing and redundant anyway, and I'm suss about his comments on power.

RxTx.bmp (222 KB)

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Thanks again Nick

Probably I should just buy this module instead? http://www.ebay.com/itm/1pcs-New-Wireless-Module-Bluetooth-Transceiver-Module-RS232-TTL-3-3V-/190877645815?pt=LH_DefaultDomain_0&hash=item2c7131bbf7

Does it not run 3.3 v? And there for their should not be any problems, when my Pro Mini runs on 3.3 v ?

From the background I read:
"The only other connections required are the standard 5v and ground. I believe all HC-05s
come with six pins. You don’t need the other two for this exercise. And yes, the HC-0x
modules are 3.3v devices but note that the JY-MCU package has all the level shifters on
board and is clearly labelled for 3.6 to 6v operation. If your Arduino is made for 3.3v
operation, read no further. "

Which might imply, that it just doesnt work, when the Pro Mini runs on 3.3v.?.

I tried applying 4.5v through RAW, but still nothing.

Kasper

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HazardsMind:

Summary

Microcontroller ATmega168
Operating Voltage 3.3V or 5V (depending on model)
Input Voltage 3.35 -12 V (3.3V model) or 5 - 12 V (5V model)
Digital I/O Pins 14 (of which 6 provide PWM output)
Analog Input Pins 8
DC Current per I/O Pin 40 mA
Flash Memory 16 KB (of which 2 KB used by bootloader)
SRAM 1 KB
EEPROM 512 bytes
Clock Speed 8 MHz (3.3V model) or 16 MHz (5V model)

Use a 5V regulator to power both. A standard 5V regulator circuit should suffice, also make sure you have the correct capacitors too.

Thanks for your reply :slight_smile:
Since I´m so new to electronics and Arduino, I dont know how and where to put capasitors. In all the guides I have found, they have just connected the Arduino and BT module directly without capacitors.

Kasper

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Kapper86:
Probably I should just buy this module instead? http://www.ebay.com/itm/1pcs-New-Wireless-Module-Bluetooth-Transceiver-Module-RS232-TTL-3-3V-/190877645815?pt=LH_DefaultDomain_0&hash=item2c7131bbf7

Does it not run 3.3 v? And there for their should not be any problems, when my Pro Mini runs on 3.3 v ?

I don't know anything about that board, I have never seen it before. Unfortunately, it seems that sellers don't know anything about it either. They claim it runs on 3.3v but there is a terminal clearly marked 5.0 and there is only one conclusion you can draw about that. I think it's a fair bet that it runs on both 3.3 and 5v - something one would think the sellers would trumpet loud and clear for all to hear, but they don't even know what bluetooth module it is. It is clearly an HC-0 something but you will never know what, until you test it.

For all that dark mystery, I would be inclined to buy it. You probably don't need an HC-05, so if it's an HC-06, which I think is likely, it is OK. It won't be any more unsuitable than what you've got.

.........And yes, the HC-0x
modules are 3.3v devices but note that the JY-MCU package has all the level shifters on
board and is clearly labelled for 3.6 to 6v operation. If your Arduino is made for 3.3v
operation, read no further. "

I'm really glad you are reading what I have written, particularly as this bit is in a state of flux, somewhat. More to the point, it appears that you are one of the gang the is moving the goalposts, and I am struggling to keep up.

Note that I refer to the JY-MCU.

Yes, the JY-MCU is clearly labelled for a 3.6 to 6v power supply, and yes, you shouldn't have much faith if you are only feeding it 3.3v. Nobody can doubt the theory but the practice may be different.

It is now clear that I was wrong to say that all the levels are fixed on the JY-MCU board. The Tx-Rx pins are marked for 3.3v operation. Don't ask why they would only do half the job. There are varying views on all of this, mine is to ignore it all. A better view is that Arduino doesn't care, so don't worry about the Rx, but Bluetooth is inherently 3.3v and might get uptight about 5v leaned against its Rx pin, so regulating Arduino's Tx to 3.3v is a good idea. I still have not done this but it would be irresponsible not to mention it, and I update that PDF pretty regularly.

Which might imply, that it just doesnt work, when the Pro Mini runs on 3.3v.?.

Well, I'm sure you can't rely on it but there is a similar thread here
http://forum.arduino.cc/index.php?topic=224113.msg1627838#msg1627838
where I reckoned the power was suss, and I was wrong - for now.

[quote}
I tried applying 4.5v through RAW, but still nothing.
[/quote]

As I understand it the RAW input allows you to put 4.5v through the Pro Mini's on-board regulator. I therefore assume you are feeding the same 4.5v to Bluetooth, and that should work - providing there is adequate current.

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