Baud Rate Error Calculator

This tool calculates the Baud Error Rate in percentage (%).

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Formula





UxBRG=(FP/(16*BR⋆))−1





where





    

  • BR* is the desired Baud Rate
    • 




  • FP is the clock frequency
    • 






UxBRG is the UART Baud Rate Generator register value.





The receive UART uses a clock that is 16 times the Baud rate (hence the number 16 in the denominator)










The actual Baud Rate is given by





BR=FP/(16*(UxBRG+1))





the Baud Rate error is given by





BRerr = ((BR⋆−BR)/BR)*100%





Example Calculation





For a clock frequency of 10 MHz and desired Baud Rate of 19200, the low and high integer value of UxBRG are 31 and 32, respectively.





The percentage Baud Rate errors associated with these values are +1.375% and -1.696%. 





The absolute value associated with the lower value of UxBRG (31) is smaller and therefore preferred. 





Background





What is Baud Rate?





Baud rate, also known as symbol rate, is a measure of the number of symbols or signal changes per second in a communication channel. It determines the transmission speed of data. Each symbol might consist of one or more bits. 





If a symbol is comprised of one bit then the Baud rate is the same as the bit rate. It a symbol includes multiple bits as is the case for high order modulation schemes, then the Baud rate is lower than the bit rate. 





Therefore, baud rate and bit rate are not always the same and can differ depending on the modulation scheme.





Baud Error rate





In UART (Universal Asynchronous Receiver Transmitter) communication, the baud rate determines the speed at which data is transmitted and received between devices.





Several factors can contribute to baud rate errors in UART communication. Examples are 





    

  • Crystal inaccuracies (use the PPM to Hz calculator to understand how this specification affects the output frequency)
    • 




  • Timing mismatches and 
    • 




  • Electrical noise. 
    • 






Minimizing these factors are critical toward ensuring accurate data transmission and reception.





Calculating the baud rate error and tolerance is essential for determining the reliability of UART communication. It involves measuring the deviation between the calculated baud rate and the actual baud rate to assess the  accuracy and stability of communication.





Determining Allowable Baud Rate Error for Reliable Communication





The allowable baud rate error defines the margin for error within which the system can maintain reliable communication. It is calculated by comparing the desired baud rate with the actual baud rate and establishing the acceptable deviation range.





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