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Disable the UDRE interrupt sooner in HardwareSerial 

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 dbe23685c2
commit f1cd85da7a
1 changed files with 12 additions and 12 deletions
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24
cores/arduino/HardwareSerial.cpp
View File

@ -223,22 +223,22 @@ void HardwareSerial::_rx_complete_irq(void)
void HardwareSerial::_tx_udr_empty_irq(void)
{
// If interrupts are enabled, there must be more data in the output
// buffer. Send the next byte
unsigned char c = _tx_buffer[_tx_buffer_tail];
_tx_buffer_tail = (_tx_buffer_tail + 1) % SERIAL_BUFFER_SIZE;
*_udr = c;
// clear the TXC bit -- "can be cleared by writing a one to its bit
// location". This makes sure flush() won't return until the bytes
// actually got written
sbi(*_ucsra, TXC0);
if (_tx_buffer_head == _tx_buffer_tail) {
// Buffer empty, so disable interrupts
cbi(*_ucsrb, UDRIE0);
}
else {
// There is more data in the output buffer. Send the next byte
unsigned char c = _tx_buffer[_tx_buffer_tail];
_tx_buffer_tail = (_tx_buffer_tail + 1) % SERIAL_BUFFER_SIZE;
*_udr = c;
// clear the TXC bit -- "can be cleared by writing a one to its bit
// location". This makes sure flush() won't return until the bytes
// actually got written
sbi(*_ucsra, TXC0);
}
}
// Constructors ////////////////////////////////////////////////////////////////