diff options
Diffstat (limited to 'cores/arduino/HardwareSerial.cpp')
| -rw-r--r-- | cores/arduino/HardwareSerial.cpp | 8 |
1 files changed, 5 insertions, 3 deletions
diff --git a/cores/arduino/HardwareSerial.cpp b/cores/arduino/HardwareSerial.cpp index 560ef3a..e6ccdef 100644 --- a/cores/arduino/HardwareSerial.cpp +++ b/cores/arduino/HardwareSerial.cpp @@ -97,8 +97,10 @@ void HardwareSerial::_tx_udr_empty_irq(void) // 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); + // actually got written. Other r/w bits are preserved, and zeroes + // written to the rest. + + *_ucsra = ((*_ucsra) & ((1 << U2X0) | (1 << MPCM0))) | (1 << TXC0); if (_tx_buffer_head == _tx_buffer_tail) { // Buffer empty, so disable interrupts @@ -225,7 +227,7 @@ size_t HardwareSerial::write(uint8_t c) // 500kbit/s) bitrates, where interrupt overhead becomes a slowdown. if (_tx_buffer_head == _tx_buffer_tail && bit_is_set(*_ucsra, UDRE0)) { *_udr = c; - sbi(*_ucsra, TXC0); + *_ucsra = ((*_ucsra) & ((1 << U2X0) | (1 << MPCM0))) | (1 << TXC0); return 1; } tx_buffer_index_t i = (_tx_buffer_head + 1) % SERIAL_TX_BUFFER_SIZE; |