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Topic: How to enter AT mode in HC-05 bluetooth module (Read 12377 times) previous topic - next topic

syntax_error

Hi guys,
I'm new to arduino and electronics so please bare with me.
I've been trying to enter AT mode with a HC-05 bluetooth module (http://www.ebay.ca/itm/180957186752?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649). This is what I did;

1. I used a USB to Serial adaptor (http://www.ebay.ca/itm/170910289160?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649).
2. Connected TX bluetooth to RX adaptor, RX bluetooth to TX adaptor (Via a voltage regulator http://www.instructables.com/id/Cheap-2-Way-Bluetooth-Connection-Between-Arduino-a/step3/Wiring-the-Arduino-Bluetooth-transceiver/).
3. Connected power (3.3v) and ground (I used a voltage regulator to bring the 5v from the adaptor down to 3.3v).
4. Then I connected pin 34 bluetooth (PIO11) to 3.3v (To make the pin go high).
5. Opened PuTTY and set it to Serial mode. Used COM8 (the USB to Serial adaptor COM port) and 9600 baud rate. (When this didn't work I also tried 38400 baud rate).
6. In the terminal section of PuTTY set Local echo to Force on.
7. Entered "AT\r\n" in PuTTY.

I didn't get an OK as the result. Did I do something wrong? Any help please?

Instructions on how to enter AT command mode (http://elecfreaks.com/store/download/datasheet/Bluetooth/HC-0305%20serail%20module%20AT%20commamd%20set%20201104%20revised.pdf)


Riva

Found a manual that's a bit easier to read here http://iteadstudio.com/Downloadfile/BluetoothHC05.pdf and as you say it states you pull pin 34 (PIO11) to VCC (3.3V) and then power on.
Quote
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).

Is your FTDI serial cable set for 3.3V or 5V

syntax_error

Thanks for replying!
My FTDI is set for 5V but I'm powering the bluetooth through a voltage divider. When I send AT\r\n I don't get anything back (no OK, the cursor in PuTTY just goes back to the beginning). Help?  :smiley-sad-blue:

Riva


Thanks for replying!
My FTDI is set for 5V but I'm powering the bluetooth through a voltage divider. When I send AT\r\n I don't get anything back (no OK, the cursor in PuTTY just goes back to the beginning). Help?  :smiley-sad-blue:

Maybe the FTDI should also be set to 3.3V as the device is 3.3V else your pumping 5V into the RX pin.
A better manual here http://www.hobbytronics.co.uk/datasheets/EGBT-bluetooth-module.pdf says at the bottom of page 7
Quote
EGBT-045MS RX input is not 5V tolerant. A schottky diode connected as shown will keep 5V volt-
ages out of the Bluetooth module when operated with a 5V host microcontroller.

formus

i'm sorry but i didnt get the idea
i have bought this bluetooth module http://ram-e-shop.com/oscmax/catalog/product_info.php?products_id=2244
i would like to pair it with another Bluetooth module
i think i just need to use AT modes for this
but i really don't know how to use this modes
i have succeed in pairing this module with pc
but this is not what i need
any help please

Riva

The link you supplied for your BT module makes me think it is a slave only device that you can only link to from another device. It is not capable of creating a link to other devices, just receiving them.
If it is a slave module (HC-06) then normally the AT commands must not have line termination (carriage return/line feed) as it uses a 1 second timeout to assume end of command.

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