UART "callibration"?

While I am likely getting in way over my head, are there any settings that can be modified on a BeagleBone black as it relates to the UART oscillator? I have seen some reference to the specification of the AM335x regarding:

The UART modules each have a 48MHz clock to generate their timing. They can be configured in one of two modes: UART 16x and UART 13x, in which that clock is divided by 16 and 13, respectively.


I am still trying to get an application I wrote to communicate with a 3rd party controller and grasping at straws at this point.I just can’t figure out why everything works fine when I go through /ttyUSB0 (using a USB-serial adapter), but when I try to utilize the /tty04 UART, I can’t communicate.

Without drowning this thread with every little thing I have done, I have come to the following conclusions:

  1. My application works because I can confirm it’s functionality when connected via USB-serial adapter
  2. My UART circuit (have tried with a MAX3232 and a MAX232) works because I can open up minicom and do a loopback test successfully. I have also communicated from mt BB to a Windows PC at the same baud rate that I am attempting to use with my application, so based on the fact that the manual communication between BB and PC was successful, I feel confident that my UART circuit is ok.
  3. Currently I have a logic analyzer hooked up and I am looking at the data I am transmitting from my BB. The applicatio I use with the analyzer decodes the protocol and the data I am seeing from my circuit is the data I am expecting to see.

This snapshot is from the USB-serial connection transmission:


This snapshot is from the UART circuit transmission:


What baud rate are you running at? The higher, the more critical the timing is.
With an oscilloscope, measure the period for a single bit, BR = 1/period
A logic analyzer will not work for this.
Even if you could change some setting, without knowing the period of a single bit, you would be guessing at the timing.


I am running at 115200. I will try and get some decent readings with my oscope. Thanks.