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Code Issues Releases Activity

Disable the UDRE interrupt sooner in HardwareSerial

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Before, the interrupt was disabled when it was triggered and it turned
out there was no data to send. However, the interrupt can be disabled
already when the last byte is written to the UART, since write() will
always re-enable the interrupt when it adds new data to the buffer.

Closes: #1008
This commit is contained in:
Matthijs Kooijman 2013-04-18 19:06:00 +02:00 committed by Cristian Maglie
parent ccd8880a37
commit 0be4e8cd3c
1 changed files with 12 additions and 12 deletions
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12
hardware/arduino/avr/cores/arduino/HardwareSerial.cpp
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@ -223,12 +223,8 @@ void HardwareSerial::_rx_complete_irq(void)
void HardwareSerial::_tx_udr_empty_irq(void) void HardwareSerial::_tx_udr_empty_irq(void)
{ {
if (_tx_buffer_head == _tx_buffer_tail) { // If interrupts are enabled, there must be more data in the output
// Buffer empty, so disable interrupts // buffer. Send the next byte
cbi(*_ucsrb, UDRIE0);
}
else {
// There is more data in the output buffer. Send the next byte
unsigned char c = _tx_buffer[_tx_buffer_tail]; unsigned char c = _tx_buffer[_tx_buffer_tail];
_tx_buffer_tail = (_tx_buffer_tail + 1) % SERIAL_BUFFER_SIZE; _tx_buffer_tail = (_tx_buffer_tail + 1) % SERIAL_BUFFER_SIZE;
@ -238,6 +234,10 @@ void HardwareSerial::_tx_udr_empty_irq(void)
// location". This makes sure flush() won't return until the bytes // location". This makes sure flush() won't return until the bytes
// actually got written // actually got written
sbi(*_ucsra, TXC0); sbi(*_ucsra, TXC0);
if (_tx_buffer_head == _tx_buffer_tail) {
// Buffer empty, so disable interrupts
cbi(*_ucsrb, UDRIE0);
} }
} }