ManuelW/grbl-LPC-CoreXY
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added asynchronous write as provided by Arthur Wolf

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This commit is contained in:
Simen Svale Skogsrud 2011-05-31 22:29:50 +02:00
parent f4c1cbac3c
commit 33a940cdf8
1 changed files with 56 additions and 6 deletions
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62
wiring_serial.c
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@ -37,10 +37,12 @@
#define RX_BUFFER_SIZE 64
#endif
#define TX_BUFFER_SIZE 16
unsigned char rx_buffer[RX_BUFFER_SIZE];
uint8_t rx_buffer_head = 0;
uint8_t rx_buffer_tail = 0;
int rx_buffer_head = 0;
int rx_buffer_tail = 0;
void beginSerial(long baud)
{
@ -60,13 +62,61 @@ void beginSerial(long baud)
// defaults to 8-bit, no parity, 1 stop bit
}
void serialWrite(unsigned char c)
{
while (!(UCSR0A & (1 << UDRE0)))
;
unsigned char tx_buffer[TX_BUFFER_SIZE];
unsigned char tx_buffer_head = 0;
volatile unsigned char tx_buffer_tail = 0;
void serialWrite(unsigned char c) {
if ((!(UCSR0A & (1 << UDRE0))) || (tx_buffer_head != tx_buffer_tail)) {
// maybe checking if buffer is empty is not necessary,
// not sure if there can be a state when the data register empty flag is set
// and read here without the interrupt being executed
// well, it shouldn't happen, right?
// data register is not empty, use the buffer
unsigned char newhead = tx_buffer_head + 1;
newhead %= TX_BUFFER_SIZE;
// wait until there's a space in the buffer
while (newhead == tx_buffer_tail) ;
tx_buffer[tx_buffer_head] = c;
tx_buffer_head = newhead;
// enable the Data Register Empty Interrupt
sei();
UCSR0B |= (1 << UDRIE0);
}
else {
UDR0 = c;
}
}
// interrupt called on Data Register Empty
SIGNAL(USART_UDRE_vect) {
// temporary tx_buffer_tail
// (to optimize for volatile, there are no interrupts inside an interrupt routine)
unsigned char tail = tx_buffer_tail;
// get a byte from the buffer
unsigned char c = tx_buffer[tail];
// send the byte
UDR0 = c;
// update tail position
tail ++;
tail %= TX_BUFFER_SIZE;
// if the buffer is empty, disable the interrupt
if (tail == tx_buffer_head) {
UCSR0B &= ~(1 << UDRIE0);
}
tx_buffer_tail = tail;
}
int serialAvailable()
{