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I run out of stock as the modules are getting popular and are used in many student projects. I expected that they will work as the modules I had ordered from DX half a year ago. I wired up a V1. But wen I tried to communicate to the module, it failed: No response back from the module, or unknown response:.

I checked all the wires, and they were looking ok. Maybe a different baud by default on the module? Maybe it has a different firmware see this post about different firmware? If it responds as HC to the host, I know it has the correct firmware on it. I can connect to it, and asks me for the Pairing Code, and it accepts the default pairing code But whatever I send from the host to the Bluetooth module, does not arrive nluetooth the microcontroller: The module did not report back to the microcontroller.

I verified this with the module connected: And all my existing modules work as expected, so it is definitely not a wiring or software issue. But then I realized: To inspect the differences, I removed the shrink tube around the board with a sharp knife cutting the tube on the side be careful! Board Top side, with the HC pin functions as I know it see this post:. With this I can see what is getting to the connector, and what ends up at the Bluetooth module itself.

Sending an AT from the Microcontroller shows that the command arrives at the Bluetooth module too:. The string from the host arrives on the Tx pin with baud too: So what is wrong that nothing arrives on the connector pin to the microcontroller? And if there are, then only for older bluetooyh like the V1. So I had no choice than to reverse engineer the connections of the SMD parts on the board: With inspecting the traces on the board and probing the contacts, bluetioth this took me a while….

The back side does not give much details, but some vias are connected to the pins of the HC module:. It will not provide any protection to the module unless your electronics were to apply a negative voltage to the Tx pin.

However, it would have a use if your electronics were powered off and the Bluetooth module stayed powered on: It would fail, of course, but many milliamps would flow and battery life would be reduced. This is a reasonable use case I think: Bluetooth module stays awake while the main electronics is powered j-mcu.


Your scope traces show it is not present. Cheap parts from China might mean that I need to be prepared for surprises: And because it is hard to get schematics, things will be hard to find a problem. I hope that this post is useful for anyone else who might receive the V1. With all the comments thanks! The solution is to pull-up the Tx signal to the microcontroller Rx for the microcontroller either with a hardware pull-up or with a software pullup.

In my example, Rx is on PTC Do you have plan to try with Bluetooth Low Enegy 4. So excited, with BLE, battery life will be very big longer. Have a read here: I was also puzzled why they would add a diode on the TxD pin.

Then the Bluetooth module will pull the jy-mxu to logic 0 through the diodes and the pull-up resistor will pull it to logic 1, and all should be well…. Hi Charles, you nailed hy-mcu Always best to have hardware and software working as a team! More seriously, it is important to look at all interfaces for this kind of thing. In general, a pull-up resistor on any input is the right starting point, as it puts a pin into a safe, defined, state if it is otherwise not connected.

Getting Bluetooth Working with JY-MCU BT_BOARD V1.06

A floating input will make unexpected transitions, and will often draw excessive current as the transistors end up in their linear region, both conducting. However, the presence of a pull-up will also draw unnecessary current if the input pin is being driven, correctly, to logic 0 by external circuitry. Then current flows to GND through the pull-up, and it is best removed, or replaced by a pull-down not available on the KL25Z.

Finally, you need to consider what happens if part of the circuitry is powered down. You will often measure about 1V on the supply rail of the chip you think is powered down. And suspect that is why the diode has appeared on your Bluetooth module. Yes, agreed, it is always the combination of hardware and software which makes things challenging. I just run into a similar problem last week with an I2C device on the bus which was switched off, but drawing too much current.

Hi Christian, I have not done formal measurement, but the modules worked fine in the meter range. And you need a two-way communication as the protocol is bidirectional. But I started to use PDD macros to set things like this. For example this enables pull-ups for PTC3: Hi erich, we have a bluetooth module support 3.

Connecting Arduino Uno and the JY-MCU Bluetooth module using SoftwareSerial

That one looks like a good module! You find my address on https: How can I do the equivalent of update 2 on an arduino board? You cannot do it the same way for the Arduino, as unfortunately there is no Processor Expert for that microprocessor family.


You need to check the details of your microprocessor manual if and how you can enable internal pull-ups. An easier way might be for you to simply add a pull-up resistor on your board.

Seems to work for me. And thanks for the article, Erich! I read about your work on it and I jy-cu pleased that you have posted so much details about it.

Getting Bluetooth Working with JY-MCU BT_BOARD V | MCU on Eclipse

It is recognized as HC So far I can send some text and can receive it on my phone terminal. I tried to wire it to 3.

The problem is that I can use the module, but I can not change the bludtooth or speed of it. Any help would be greatly appreciable! Hi Stoyan, is the red LED flashing or always on?

In transparent mode the AT commands are not recognized. Otherwise I suggest you check with a logic analyzer what is going on? See as well https: Hi Erich, Thanks for the reply! After successful connection the pattern changes to 2 flashing and big pause. From what I can see is that I can not make the module to get into AT command mode. I have tried with the KEY pin with 3.

Blutooth will check the links and will try it again. I will keep you posted! Hi Stoyan, you only can send AT commands to the module as long it is blinking. And the AT commands have to be sent from the microcontroller attached, not from the PC. The Key pin is only supported and connected on special firmware, not on most of the modules available for cheap.

That 2 flashing and pause sounds like an error code of the module, I have never seen that. I have tried another approach. It seems that the module gets into some special mode — I have a different LED pattern. So far Jy-mu have the following: Now when the Key is up 3.

Easy Arduino Bluetooth Communication with JY-MCU Bluetooth module

Interesting is that I can no longer connect to the module, through phone or other Bluetooth module. I will keep you posted bluetolth my progress. Any thoughts on it will be greatly appreciable.

Have you had a look at the schematic of the board already? I have recently purchased HC bluetooth modulei am have connected with Arduino Uno board.

After connection red LED is blinking but i am not able to connect to my phone bluetooth lz help. If the red LED is blinking, then no connection has been made, so it bleutooth clear that it does work for you. Please try it first with your PC.