diff --git a/sys/riscv/sifive/sifive_uart.c b/sys/riscv/sifive/sifive_uart.c --- a/sys/riscv/sifive/sifive_uart.c +++ b/sys/riscv/sifive/sifive_uart.c @@ -137,9 +137,15 @@ static int sfuart_rxready(struct uart_bas *bas) { - - return ((uart_getreg(bas, SFUART_RXDATA) & - SFUART_RXDATA_EMPTY) == 0); + /* + * Unfortunately the FIFO empty flag is in the FIFO data register so + * reading it would dequeue the character. Instead, rely on the fact + * we've configured the watermark to be 0 and that interrupts are off + * when using the low-level console function, and read the interrupt + * pending state instead. + */ + return ((uart_getreg(bas, SFUART_IRQ_PENDING) & + SFUART_IRQ_PENDING_RXQM) != 0); } static int