UART BAUDRATE register values

Question

What is the formula for calculation of values for the UART BAUDRATE register from bit rates?

Håkon Alseth · Accepted Answer

Hi Bengt, 
 note : this formula is simplified and may differ from the actual baudrate measurement 
 The formula is:
Baudrate = desired baudrate * 2^32 / 16000000 
 Example:
Baudrate of 31250 should then be 8388608 decimal = 0x800000. 
 Note that you will have to round the number afterwards:
rounded_value = (value + 0x800) & 0xFFFFF000 
 Since the baudrate generator will be sourced by the 16 M (Either RC or XOSC, depending on your configuration), then your error rate will be ~equal to the overall drift of the system clock and the accuracy of the baudrate generator towards your target baudrate. 
 Other way around:
Check out this define in nrf51_bitfields.h line 5702: 
 UART_BAUDRATE_BAUDRATE_Baud115200 (0x01D7E000UL) /*!< 115200 baud. */ 
 The actual baudrate set with the above define is: 
 baudrate_reg_val * 16M / 2^32 = 115203.86 baud. 
 Best regards
Håkon

UART BAUDRATE register values

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