change baud rate


Im not an expert but wonder how it is possible to change the default baud rate from 19200 to 115200? I use an Arduino Pro Mini 5V and 3V3 on a Mac 10.5.7

I have been looking inside the preference file and hardware directory but dont understand much. (burn bootloader??)

One more thing: To run my boards on 19200 I need to write 9600 in the code:

void setup() {
  //start serial


I have this info:

avrdude: Version 5.4-arduino, compiled on Oct  9 2007 at 11:20:31
Copyright (c) 2000-2005 Brian Dean,

System wide configuration file is
User configuration file is "/Users/boyeriis/.avrduderc"
User configuration file does not exist or is not a regular file,

Using Port                  : /dev/tty.usbserial-A6004kUg
Using Programmer            : stk500v1
Overriding Baud Rate        : 57600
avrdude: Send: 0 [30]   [20]
avrdude: Send: 0 [30]   [20]
avrdude: Send: 0 [30]   [20]
avrdude: Recv: . [14]
avrdude: Recv: . [10]
AVR Part                    : ATMEGA328P
Chip Erase delay            : 9000 us
PAGEL                       : PD7
BS2                         : PC2
RESET disposition           : dedicated
RETRY pulse                 : SCK
serial program mode         : yes
parallel program mode      : yes
Timeout                    : 200
StabDelay                   : 100
CmdexeDelay                 : 25
SyncLoops                   : 32
ByteDelay                    : 0
PollIndex                    : 3
PollValue                   : 0x53
Memory Detail


Any suggestion?

Thanks :D

What are you doing? / What speed do you want to change?

If "Serial.begin(9600);" is getting you a speed of 19200, then you may have your board set incorrectly. The baud-rate of the Arduino is calculated from the CPU frequency. There are two versions of the Arduino Pro Mini, a 5V 16MHz version, and a 3.3V 8MHz version. If you have the 16Mhz board, you probably want to select the Diecimila board, since it is closest to the 16Mhz Mini Pro.

9600baud * ( 16MHz / 8MHz ) = 19200baud

Thanks a lot! This make sense :D

Yeah, there's a problem with the bootloader on the 8MHz devices. Luckily it is easily solved by the updated (but not officially) HardwareSerial.

See this thread for details.