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Topic: Understanding Baud Rate (Read 824 times) previous topic - next topic

jjspierx

I understand what baud rate is, but I am trying to find out if there is ever a reason to use a lower baud rate (9600) vs. a higher baud rate (115200).  Assuming the devices that the data is being transferred between are capable of the higher speed (115200) why would anyone ever use a lower baud rate?  I see many sketch examples that by default set the baud rate to 9600 and it makes me think there is a reason why people are using the lower rate.  Is the data more reliable at lower baud rates, less prone to communication errors?

Thank you in advance.

CrossRoads

If you have crummy cabling, or long distances, poor grounding, noisy environment, then slower baud rates can give more reliable results. Slower also uses less power as CMOS power consumption is switching frequency dependent.
If the serial comm's are buffered first, so that RS232 type levels (+/- 3 to +/-12V, one wire for send, one for receive, plus Gnd) or RS485 type signals (+/-3V, but with 2 wires for sending, 2 for receiving, plus Gnd) than higher speeds and longer distances can be supported more reliably.
Designing & building electrical circuits for over 25 years. Check out the ATMega1284P based Bobuino and other '328P & '1284P creations & offerings at  www.crossroadsfencing.com/BobuinoRev17.
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PaulS

Quote
I see many sketch examples that by default set the baud rate to 9600 and it makes me think there is a reason why people are using the lower rate.

When hacking out an example,
Code: [Select]
Serial.begin(9600);
is easier to type than
Code: [Select]
Serial.begin(115200);

Jack Christensen

I do a fair number of projects with XBees and I always use 115200 baud if the MCU clock is 16MHz, and 57600 if the clock is 8MHz. My thinking is the less time spent managing communications, the better, and more time to do other things, although due to buffering etc., it probably makes precious little if any difference in my projects. But that's just the way I think.
MCP79411/12 RTC ... "One Million Ohms" ATtiny kit ... available at http://www.tindie.com/stores/JChristensen/

robtillaart

Quote
it makes me think there is a reason why people are using the lower rate.

- because it is used in so many samples
- because it is one of the basic speeds of the original VT52 terminal
- because it is the most supported
- ...

note that in digital communication 1 baud == 1 bit per second and in analog communication 1 baud == 1 discrete signal.
So an analog line that communicates with 16 different voltages can fit 4 bits of info per voltage.  A 1000 baud line would allow 4000 bits.
Rob Tillaart

Nederlandse sectie - http://arduino.cc/forum/index.php/board,77.0.html -
(Please do not PM for private consultancy)

retrolefty


Quote
I see many sketch examples that by default set the baud rate to 9600 and it makes me think there is a reason why people are using the lower rate.

When hacking out an example,
Code: [Select]
Serial.begin(9600);
is easier to type than
Code: [Select]
Serial.begin(115200);


Yep, save those key strokes and help save the planet.  =(

Lefty

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