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Re-enable interrupts before directly enqueuing characters in the UART FIFO.

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Not sure why, but this reduces the occurrence rate of an occasional ~3.25 or
~7μs intercharacter delay, which was interfering with use of the UART to
generate precise timing pulses (such as driving WS2812 LEDs).
This commit is contained in:
Christopher Pascoe 2015-12-28 12:17:18 -05:00
parent 4b90db41fe
commit e147314f97
1 changed files with 5 additions and 1 deletions
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6
cores/esp8266/HardwareSerial.cpp
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@ -627,12 +627,13 @@ size_t HardwareSerial::write(uint8_t c) {
return 0;
_written = true;
bool tx_now = false;
while(true) {
{
InterruptLock il;
if(_tx_buffer->empty()) {
if(uart_get_tx_fifo_room(_uart) > 0) {
uart_transmit_char(_uart, c);
tx_now = true;
} else {
_tx_buffer->write(c);
uart_arm_tx_interrupt(_uart);
@ -644,6 +645,9 @@ size_t HardwareSerial::write(uint8_t c) {
}
yield();
}
if (tx_now) {
uart_transmit_char(_uart, c);
}
return 1;
}