1 files changed, 94 insertions, 0 deletions
diff --git a/kernel/serial/serial.c b/kernel/serial/serial.c
new file mode 100644
index 0000000..6e88cd6
--- /dev/null
+++ b/kernel/serial/serial.c
@@ -0,0 +1,94 @@
+#include <avr/interrupt.h>
+#include "serial/serial.h"
+#include "sched/sched.h"
+#include "bug/debug.h"
+
+static struct serial_device_t serial = SERIAL_DEVICE_INIT(serial);
+
+void serial_init(unsigned long baud) {
+  UCSR0A |= (1 << U2X0);   //enable double speed transmission
+  uint16_t baud_setting = (F_CPU / 4 / baud - 1) / 2;
+  UBRR0H = baud_setting >> 8;
+  UBRR0L = baud_setting;
+  UCSR0B |= (1 << RXEN0) | (1 << TXEN0) | (1 << RXCIE0); // 8-bit, no parity, 1 stop bit
+  UCSR0B &= ~(1 << UDRIE0);
+}
+
+static inline int rbuffer_empty_safe(struct rbuffer_t* const rb) {
+  cli();
+  int r = rbuffer_empty(rb);
+  sei();
+  return r;
+}
+
+size_t serial_read(char* const data, size_t size) {
+ while (rbuffer_empty_safe(&serial.rx_buffer)) {
+    cli();
+    sleep_on(&serial.rx_q);
+    yield();
+  }
+  cli();
+  size_t r = rbuffer_read(&serial.rx_buffer, data, size);
+  sei();
+  return r;
+}
+
+
+//called when byte is received
+ISR(USART0_RX_vect, ISR_NAKED) {
+  SAVE_CONTEXT();
+  char c = UDR0;
+  rbuffer_write_char(&serial.rx_buffer, c);
+  wake_all(&serial.rx_q);
+  RESTORE_CONTEXT();
+  asm volatile ("reti");
+}
+
+
+size_t serial_write(const char* const data, size_t size) {
+  cli();
+  size_t r = rbuffer_write(&serial.tx_buffer, data, size);
+  sei();
+  UCSR0B |= (1 << UDRIE0);
+  return r;
+}
+
+//called when data register is empty
+ISR(USART0_UDRE_vect) {
+  char c;
+  if (rbuffer_read_char(&serial.tx_buffer, &c)) {
+    UDR0 = c;
+  } else {
+    UCSR0B &= ~(1 << UDRIE0); //buffer empty, disable interruot
+  }
+}
+/*
+void serial_read() {
+  ENTER_CRITICAL();
+  list_move_tail(&current->list, &serial_rx_q);
+  EXIT_CRITICAL();
+  yield();
+}
+*/
+/*
+void serial_write_str(const char* const str) {
+  for (size_t i = 0; str[i] != '\0'; ++i) {
+    ENTER_CRITICAL();
+    rbuffer_write(&serial_dev.tx_buffer, str[i]);
+    EXIT_CRITICAL();
+    UCSR0B |= (1 << UDRIE0);
+  }
+}*/
+
+
+/*
+ISR(INT3_vect, ISR_NAKED) {
+  SAVE_CONTEXT();
+  if (!list_empty(&serial_rx_q)) {
+    list_move_tail(serial_rx_q.next, &ready);
+  }
+  schedule();
+  RESTORE_CONTEXT();
+  asm volatile ("reti");
+}
+*/