Hi there
I'm using the HC-05 Bluetooth module but I'm confused about the TX,RX pins.
I want to know when should I connect the RX to a divider circuit to convert 5v to 3.3v.
Because while searching, I saw both of the following:
- either RX is connected to TX of the UNO and TX is connected to RX of the UNO without a divider circuit.
- or RX is connected to a divider circuit and then connected to any digital pin , TX is connected to any digital pin as well.
So can you give me a thought about both the situations?
my thought is that only digital pins needs a divider rule, but the TX,RX pins can be connected directly and operates without any problems but if so, then what's the difference between both??
Note that I'm using HC-05 to turn on a LED.
Hope to see some good explanation that suits a new Arduino learner.
Thank you..
Hello Abdulla.
The Arduino RX/TX pins are the hardware serial port. A software serial port uses any of the other digital pins. You can use either method for communication between the Arduino and the HC-05. The sketch must use the correct statements to match the method used.
The need for a voltage divider doesn't depend on which pins are used.
The Arduino TX operates at 5v and the HC-05 is rated for 3.3v. That is why a voltage divider is used -- to reduce the TX signal from 5v to 3.3v.
The HC-05 TX pin operates at 3.3v. That will not harm the Arduino and 3.3v is good enough fro logic purposes.
It is often said on this forum that the voltage divider isn't really necessary. I have not used it on any of the HC-05 devices I've made.
I hope that helps.
John.
This is the working connection diagram (Fig-1) between UNO and HC-05BT at 9600 Bd.
Figure-1:
HillmanImp:
Hello Abdulla.
The Arduino RX/TX pins are the hardware serial port. A software serial port uses any of the other digital pins. You can use either method for communication between the Arduino and the HC-05. The sketch must use the correct statements to match the method used.
The need for a voltage divider doesn't depend on which pins are used.
The Arduino TX operates at 5v and the HC-05 is rated for 3.3v. That is why a voltage divider is used -- to reduce the TX signal from 5v to 3.3v.
The HC-05 TX pin operates at 3.3v. That will not harm the Arduino and 3.3v is good enough fro logic purposes.
It is often said on this forum that the voltage divider isn't really necessary. I have not used it on any of the HC-05 devices I've made.
I hope that helps.
John.
ok that seems good.
but does it means that I can't use the TX,RX for a software serial ?
because I'm using proteus simulator to turn on the LED without using hardware(USB), just depending on the software serial process and then connected it to the TX,RX pins on the UNO.
and off course made a voltage divider for the RX on the HC-05.
You NEVER use Arduino's Tx,Rx pins for software serial. If you want to use software serial, simply choose any other pins for that.
Alternatively, you can use hardware serial, i.e. serial, and leave the wiring where it is. This means
- delete all reference to software serial
- have Bluetooth disconnected when you upload the code.
John above has explained all you need to know about dividers. It is good practice, you are already doing it right, so you might as well keep doing it!