serialTool | 一个简单的web串口工具 | Wrapper library

I am playing around with a DFRobot Romeo board that has an ATmega328p MCU on it.

I wrote a program to transmit the binary and decimal representation of 4 DIP switches wired as inputs into PORTD (PD2 -> PD5). UART is wired to PORTD, PD0 (Rx) and PD1 (Tx).

The program works as expected except for when the program first runs the terminal emulator I am using on my Mac appears to receive and display the following binary/decimal number: 00000011 3, then 00000000 0 appears, or whatever number is set by the DIP switches.

If I reset the controller with the UART connection maintained, I get the same result over and over. The terminal emulator I am using is CoolTerm. I get the same result even if I flush the buffer before reconnecting. The same result is occurring if I try another terminal emulator (i.e. Serial, SerialTools).

I reviewed my code, and do not see any obvious errors. I contacted a peer who says he has seen this behaviour as well, but has no suggestions for a solution other than clearing the terminal buffer. I have also tried a few different physical configurations such as powering the board by USB only, powering the board from a separate power supply without the USB programming cable connected, and with the USB cable connected. I get the same results on the Terminal.

Can someone take a look at this and offer a suggestion as to why this behaviour is occurring?

Here is the C code for the program.