RP2_TXRX_CTL_LOOP_m
RP2_TXRX_CTL_DTR_m | RP2_TXRX_CTL_RTS_m | RP2_TXRX_CTL_LOOP_m,
((mctrl & TIOCM_LOOP) ? RP2_TXRX_CTL_LOOP_m : 0));