Electronic – Connecting BeagleBone Black using serial port – voltage

Strangely it seems as though the Arduino is outputting voltage over both RX and TX, while the BBB is only outputting voltage on the TX line.

My guess is that the bi-directional LLC isn't able detect which direction communication is supposed to happen, and so the BBB isn't able to transmit to the Arduino.

This Sparkfun LLC is the same as the one I'm using on the BBB -> Arduino channel, but the Arduino -> BBB side just uses a voltage divider. I rigged up this setup, and it seems to be working now.

Using the version 3.8 or higher of the Linux Kernel, you can set a Device Tree Overlay.

By this method, at runtime, you can incorporate the system device drivers.

Personally, I implemented the necessary hardware to operate with a RS-485 interface and Modbus protocol. This basically is the hardware for Bus transceiver and its associated components. When I wanted to start the operation, I could see that the ttyO4 port was not enabled.
I found the solution here, where the code is presented to compile an Overlay to enable the port ttyO4. Once implemented this, everything worked properly.

Attention

In Beaglebone board I used, the operating system installed was Ubuntu. When compiling the file with the Overlay, compilation tool threw an error concerning did not recognize the option "@". This is solved, and here's how to apply the patch for the Overlay compiler. Therefore, I recommend the Overlay compiler what you obtain source code instead of using a repository.