Why can’t I change to 76800 baud rate on PC?

Q: Why can’t we change to a 76800 baud rate on a PC but are able to on some devices?

A: The reason for this is that the the standard 16C550 PC UART is too slow to keep up with the signals coming in and out. 76800 is not a standard multiple of the UART clock frequency.

Devices can be customized and therefore allow baud rates of 76800. If your PC has a customizable COM port card where you can program the bit clock then you would be able to set this value.

There is no fix for this, but if you find a converter that can change 76800 to a higher UART this could be a work around.

The standard frequencies are:

  • 150
  • 300
  • 1200
  • 2400
  • 4800
  • 9600
  • 19200
  • 38400
  • 115000