Re: Harmony v2 DRV_USART0_WriteByte stuck at 9 charc
1. The PIC32 have FIFOs on UART Tx/Rx. Your writes will fill up the Hardware FIFO and then fail discarding further data immediately. Amount of data that gets out depnds on UART data rate, FIFO size, PIC system clock, and any flow control.
2. Some PIC's have UART hardware issues, see the PIC's errata on microchip webpage near PIC32 datasheet. Read about things that can happen with UART for your PIC (Possible glitch upon overflow).
3. Simple: printf or other output routine writes data to a buffer (i.e. Ring Buffer, see wikipedia). Then periodically your main loop (app.c) checks if space in FIFO and copies data from ring buffer to FIFO (using write to UART function). The UART is so slow compared to PIC this works fine in most cases, without any Tx Interrupt, and without ever overflowing the Tx FIFO (Rx Interrupt is useful to prevent Rx overflow).
4. If you are using Tx Interrupt then you may miss an interrupt upon Tx overflow and then not get further interrupts - you need to handle such cases in your code, or do like (3) above.
5. Harmony has a few ways of handling FIFO, above is for raw byte transfer. Feel free to try the other harmony methods.