Software Uart Vs Hardware Uart. They made some changes between rev 14 and 15 to facility this functionality so the jumper settings between the two are different. Software UART may use P15 as TXD P20 or P23 as RXD wire them to the Application UART pins of the EMULATION section of the board.
It sends data bits one by one from the least significant to the most significant framed by start and stop bits so that precise timing is handled by the communication channel. The USI hardware on ATTinys is actually really good for UART functionality. These drivers were written in conformance to the DSPBIOS IOM device driver model and APIs.
Assume you have available a function called wait_usfloat WaitTime that waits for WaitTime microseconds before continuing.
Complete functions init_portB and serial_sendchar my_txt to implement the UART protocol in software. They made some changes between rev 14 and 15 to facility this functionality so the jumper settings between the two are different. Mostly this severely uses up the CPU power depending on the communication speed. A universal asynchronous receiver-transmitter UART ˈ juː ɑːr t is a computer hardware device for asynchronous serial communication in which the data format and transmission speeds are configurable.