Eugene Hutorny

Most of recent mainstream motherboards have USART chip supporting speeds above 115200. However, there are few obstacles.

First of all standard MS driver for COM port does not support baud rates above 115200. This can be easily overcome with installing a third-party driver. Currently I am using Serial XP by Leo Yuriev. Another diver I have tried is HiSerial.

Secondly, analog part of the COM port hardware may not be capable to work on high speeds. This can be easily detected with a simple hardware loop test. Even if the test did not show good results it may only mean that COM line driver is not powerful enough and it may worth testing only COM port receiver

Thirdly, RS232 level converter must be capable to work on high speed. This post provides some test results on various level converters.

Fourthly, PIC must produce good bit timing, so data are not corrupted. This post gives some technique to overcome this issue.