diff options
Diffstat (limited to 'arduino/ace_old/physical.c')
-rw-r--r-- | arduino/ace_old/physical.c | 61 |
1 files changed, 61 insertions, 0 deletions
diff --git a/arduino/ace_old/physical.c b/arduino/ace_old/physical.c new file mode 100644 index 0000000..17e15d7 --- /dev/null +++ b/arduino/ace_old/physical.c @@ -0,0 +1,61 @@ +#include "physical.h" +#include "link.h" + +#include <avr/interrupt.h> + +typedef struct { + uint8_t buffer[SERIAL_BUFFER_SIZE]; + volatile uint16_t head; + volatile uint16_t tail; +} ring_buffer; + +static ring_buffer tx_buffer = {{0}, 0, 0}; + + +void init_physical_layer(uint32_t baud) { + //enable double speed transmission + UCSR0A |= (1 << U2X0); + + uint16_t baud_setting = (F_CPU / 4 / baud - 1) / 2; + // assign the baud_setting, a.k.a. ubbr (USART Baud Rate Register) + UBRR0H = baud_setting >> 8; + UBRR0L = baud_setting; + + // defaults to 8-bit, no parity, 1 stop bit + UCSR0B |= (1 << RXEN0) | (1 << TXEN0) | (1 << RXCIE0); + UCSR0B &= ~(1 << UDRIE0) | (1 << TXEN0) | (1 << RXCIE0); +} + + +//receive +ISR(USART0_RX_vect) { + uint8_t c = UDR0; + from_physical_layer(c); +} + +//data register empty +ISR(USART0_UDRE_vect) { + if (tx_buffer.head == tx_buffer.tail) { + //buffer empty, disable interruot + UCSR0B &= ~(1 << UDRIE0); + } else { + uint8_t c = tx_buffer.buffer[tx_buffer.tail]; + tx_buffer.tail = (tx_buffer.tail + 1) % SERIAL_BUFFER_SIZE; + UDR0 = c; //write next byte + } +} + +void to_physical_layer(uint8_t byte) { + uint16_t i = (tx_buffer.head + 1) % SERIAL_BUFFER_SIZE; + + // If the output buffer is full, there's nothing for it other than to + // wait for the interrupt handler to empty it a bit +if (i == tx_buffer.tail) return; + //while (i == tx_buffer.tail) {}; + + tx_buffer.buffer[tx_buffer.head] = byte; + tx_buffer.head = i; + + //enable data register empty interrupt + UCSR0B |= (1 << UDRIE0); +}; |