Achieve baud rate 921600

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Soon Heng 21 years ago

Hi,

How is it possible to achieve fast serial baud rate of

115200,230400,460800,921600? I was trying to communicate with the PC at these rates. Using a 20MHz clock frequency is not possible due to deviation errors? What actually affects the desired baud rate, and how do I achieve this common PC standards??

Thks Heng

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Meindert Sprang 21 years ago

deviation

Use a 18.432 MHz clock.

Meindert

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Thad Smith 21 years ago

That is 20x the max bit rate. If the UART wants a 8x clock, 14.7456 MHz (16x) would work better.

Thad

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Blood and Ashes 21 years ago

I use these most often with uC's for higher speeds (8052 derivitives):

22,118,400 = 115200 baud PCON.7 = 1 TH = 0xFF 24,576,000 = 128000 baud PCON.7 = 1 TH = 0xFF

If the processor your using can handle it then:

49,152,000 = 256000 baud PCON.7 = 1 TH = 0xFF 44,236,800 = 230400 baud PCON.7 = 1 TH = 0xFF

These crystal frequencies are commonly available. I never bothered to calculate higher baud rates because of OS support issues and stability problems. USB is the way to go for improved speed.

18,432,000 is a good all-round frequency (18,432,000 = 300, 600, 1200, 2400, 4800, 9600, 19200) but I prefer 22,118,400, you can easily get quite a few of the common baud rates from it (22,118,400 = 300, 600, 1200, 1800, 2400, 4800, 7200, 9600, 14400, 19200, 38400, 57600, 115200).

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Achieve baud rate 921600

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