Skip to main content


Returns event flags set by the previous UART transaction


Device (from impOS™ 30)


Integer — the UART transaction event flags bitfield


This method returns an integer combining the event flags detected — each flag represents a single bit in the returned value. The event flags are cleared after being read.

Event Flag Constant Value Description Notes
READ_READY 1 Data is available to be read As per the default callback
WRITE_DONE 2 Transmit completed An asynchronous alternative to uart.flush()
NOISE_ERROR 4 Noise was detected in the start bit
FRAME_ERROR 8 A framing error occurred The designated start and stop bits could not be found
PARITY_ERROR 16 A parity error occurred The parity of the number of 1 bits disagrees with that specified by the parity bit
OVERRUN_ERROR 32 An over-run error occurred The receive buffer was full when another character arrived
LINE_IDLE 64 Line idle was detected This is triggered by an entire frame of 1s followed by the start bit of the next frame which contains data
WRITE_HALF_DONE 128 TX FIFO half full This is triggered when the UART transmission buffer crosses the half-full point. From impOS release 32 onwards

The values assigned to the constants may change in a future impOS™ release.