# HC 05 Bit rate, baud rate and frequency?

1. I have search the frequency at which the bit are transmitted between a arduino and a HC05, the datasheet does not tell. How can you find this frequency? 2.When I set the baud rate in the arduino, I put to 9600 symbols per second, it send one bit at a time so the bit rate is also 9600 bits per second?
1. I have search the frequency at which the bit are transmitted between a arduino and a HC05, the datasheet does not tell. How can you find this frequency?

The frequency would depend on how often your mysterious code calls a method that calls write().

2.When I set the baud rate in the arduino, I put to 9600 symbols per second, it send one bit at a time so the bit rate is also 9600 bits per second?

Yes. Don't forget any start and stop bits are included, so the number of characters per second is less than the number of bits divided by 8.

-I did not understood

PaulS: The frequency would depend on how often your mysterious code calls a method that calls write().

-There are 1 start bit, 8 data bit and 1 stop bit so character per second is 9600/10=960?

tahmod: -I did not understood

PaulS: The frequency would depend on how often your mysterious code calls a method that calls write().

-There are 1 start bit, 8 data bit and 1 stop bit so character per second is 9600/10=960?

You had two questions. Your first question did not seem to have anything to do with baud rates. If you want an Arduino to send bits to a HC05 you have to write code to make one of the Arduino I/O pins go HIGH LOW HIGH LOW etc. The number of bits per second depends on how fast your code changes the Arduino output pin.

Edit to add ... The above may be all nonsense. I thought you were referring to a 74HC05 logic chip, but I think you may be referring to a Bluetooth device - in which case baud rates are relevant.

Your calculation about 9600 baud giving 960 characters per second is correct in theory. In practice it may be a little slower. You would have to write some code to measure the actual speed. In my experience you calculation gives a good enough answer for practical purposes.

...R

My question is similar.

I build a datalogger and want to know what is the frequency of my measuring. If I understand the replys correctly, so I should (in theory) by a baud-rate of 9600 -> 64 Hz:

960 characters in a second. I measure the acceleration in 3 axis and temperature. I've got for every measruement signal 3 characters and between every signal is a " , " that means in sum: 15 characters

960/15 = 64 Hz

Is that correct?

That seems right.

Of course if you could use a higher baud rate you could send your data more often.

This is a good example where it is very easy to write a test program to measure the throughput for yourself.

...R