ManuelW/grbl-LPC-CoreXY
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More '%' modulo opertor removals and some housecleaning.

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- Serial functions contained quite a few modulo operations that would
be executed with high frequency when streaming. AVR processors are very
slow when operating these. In one test on the Arduino forums, it showed
about a 15x slow down compared to a simple if-then statement. -
Clarified some variable names and types and comments.
This commit is contained in:
Sonny J
2011-09-15 20:32:15 -06:00
parent 4d03c4febc
commit 110faae986
5 changed files with 19 additions and 16 deletions
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11
serial.c
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@ -67,7 +67,8 @@ void serial_init(long baud)
void serial_write(uint8_t data) {
// Calculate next head
uint8_t next_head = (tx_buffer_head + 1) % TX_BUFFER_SIZE;
uint8_t next_head = tx_buffer_head + 1;
if (next_head == TX_BUFFER_SIZE) { next_head = 0; }
// Wait until there's a space in the buffer
while (next_head == tx_buffer_tail) { sleep_mode(); };
@ -90,7 +91,7 @@ SIGNAL(USART_UDRE_vect) {
// Update tail position
tail ++;
tail %= TX_BUFFER_SIZE;
if (tail == TX_BUFFER_SIZE) { tail = 0; }
// Turn off Data Register Empty Interrupt to stop tx-streaming if this concludes the transfer
if (tail == tx_buffer_head) { UCSR0B &= ~(1 << UDRIE0); }
@ -104,7 +105,8 @@ uint8_t serial_read()
return SERIAL_NO_DATA;
} else {
uint8_t data = rx_buffer[rx_buffer_tail];
rx_buffer_tail = (rx_buffer_tail + 1) % RX_BUFFER_SIZE;
rx_buffer_tail++;
if (rx_buffer_tail == RX_BUFFER_SIZE) { rx_buffer_tail = 0; }
return data;
}
}
@ -112,7 +114,8 @@ uint8_t serial_read()
SIGNAL(USART_RX_vect)
{
uint8_t data = UDR0;
uint8_t next_head = (rx_buffer_head + 1) % RX_BUFFER_SIZE;
uint8_t next_head = rx_buffer_head + 1;
if (next_head == RX_BUFFER_SIZE) { next_head = 0; }
// Write data to buffer unless it is full.
if (next_head != rx_buffer_tail) {