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