From f9f1d3af3ce73c7456a51503d3f7c7dcae0b75e7 Mon Sep 17 00:00:00 2001 From: "David A. Mellis" Date: Tue, 28 Aug 2012 08:02:54 -0400 Subject: [PATCH] Serial.flush() waits for last character to be transmitted (michele.mazzucchi) http://code.google.com/p/arduino/issues/detail?id=871 --- hardware/arduino/cores/arduino/HardwareSerial.cpp | 10 ++++++++-- hardware/arduino/cores/arduino/HardwareSerial.h | 1 + 2 files changed, 9 insertions(+), 2 deletions(-) diff --git a/hardware/arduino/cores/arduino/HardwareSerial.cpp b/hardware/arduino/cores/arduino/HardwareSerial.cpp index f40ddee06..867bc9e22 100644 --- a/hardware/arduino/cores/arduino/HardwareSerial.cpp +++ b/hardware/arduino/cores/arduino/HardwareSerial.cpp @@ -327,6 +327,8 @@ try_again: *_ubrrh = baud_setting >> 8; *_ubrrl = baud_setting; + transmitting = false; + sbi(*_ucsrb, _rxen); sbi(*_ucsrb, _txen); sbi(*_ucsrb, _rxcie); @@ -376,8 +378,9 @@ int HardwareSerial::read(void) void HardwareSerial::flush() { - while (_tx_buffer->head != _tx_buffer->tail) - ; + // UDR is kept full while the buffer is not empty, so TXC triggers when EMPTY && SENT + while (transmitting && ! (*_ucsra & _BV(TXC0))); + transmitting = false; } size_t HardwareSerial::write(uint8_t c) @@ -394,6 +397,9 @@ size_t HardwareSerial::write(uint8_t c) _tx_buffer->head = i; sbi(*_ucsrb, _udrie); + // clear the TXC bit -- "can be cleared by writing a one to its bit location" + transmitting = true; + sbi(*_ucsra, TXC0); return 1; } diff --git a/hardware/arduino/cores/arduino/HardwareSerial.h b/hardware/arduino/cores/arduino/HardwareSerial.h index bf4924c6d..5bceb750b 100644 --- a/hardware/arduino/cores/arduino/HardwareSerial.h +++ b/hardware/arduino/cores/arduino/HardwareSerial.h @@ -43,6 +43,7 @@ class HardwareSerial : public Stream uint8_t _rxcie; uint8_t _udrie; uint8_t _u2x; + bool transmitting; public: HardwareSerial(ring_buffer *rx_buffer, ring_buffer *tx_buffer, volatile uint8_t *ubrrh, volatile uint8_t *ubrrl,