1 files changed, 103 insertions, 0 deletions
diff --git a/arduino/ace_old/link.c b/arduino/ace_old/link.c
new file mode 100644
index 0000000..408e14e
--- /dev/null
+++ b/arduino/ace_old/link.c
@@ -0,0 +1,103 @@
+#include "link.h"
+#include "physical.h"
+
+#include <stdlib.h>
+#include <stdio.h>
+#include <stdbool.h>
+
+typedef enum {
+  WAITING,
+  RECEIVING,
+  ESCAPING
+} link_state;
+
+#define FRAME_ESCAPE 0x02
+#define FRAME_START 0x03
+#define FRAME_END 0x10
+
+
+void from_physical_layer(uint8_t byte) {
+  static link_state state = WAITING;
+  static uint16_t position = 0; //read position
+  static uint8_t packet_data_buffer[MAX_PACKET_SIZE];
+  static packet received = {packet_data_buffer, 0};
+  static uint8_t checksum = 0x00;
+  
+  static bool previous_exists = false;
+  static uint8_t previous_byte;
+  
+  #define start_receiving() \
+    position = 0; \
+    previous_exists = false; \
+    checksum = 0x00
+  
+  #define accept(byte) \
+    if (position >= MAX_PACKET_SIZE) {start_receiving(); return;} \
+    if (previous_exists) { \
+      packet_data_buffer[position] = previous_byte; \
+      position = position + 1; \
+      checksum = checksum ^ previous_byte; \
+      previous_byte = byte; \
+    } else { \
+      previous_byte = byte; \
+      previous_exists = true; \
+    }
+    
+
+  switch(state) {
+    case ESCAPING:
+      accept(byte);
+      state = RECEIVING;
+      break;
+      
+    case WAITING:
+      if (byte == FRAME_START) {
+        start_receiving();
+        state = RECEIVING;
+      }
+      break;
+    case RECEIVING:
+      switch(byte) {
+        case FRAME_ESCAPE:
+          state = ESCAPING;
+          break;
+        case FRAME_START:
+          start_receiving();
+          break;
+        case FRAME_END:
+          state = WAITING;
+          uint8_t sent_checksum = previous_byte;
+          if (sent_checksum == checksum) {
+            received.length = position;
+            from_link_layer(&received);
+          }
+          
+          break;
+        default:
+          accept(byte);
+          break;
+      }
+  }
+  
+  #undef accept
+  #undef start_receiving
+}
+
+void to_link_layer(packet* s) {
+  uint8_t checksum = 0x00;
+  uint8_t byte;
+  int i;
+  
+  to_physical_layer(FRAME_START);
+  for (i = 0; i < (s->length); ++i) {
+    byte = s->data[i];
+    if (byte == FRAME_START || byte == FRAME_END || byte == FRAME_ESCAPE)
+      to_physical_layer(FRAME_ESCAPE);
+    checksum = checksum ^ byte;
+    to_physical_layer(byte);
+  }
+  if (checksum == FRAME_START || checksum == FRAME_END || checksum == FRAME_ESCAPE)
+    to_physical_layer(FRAME_ESCAPE);
+  to_physical_layer(checksum);
+  to_physical_layer(FRAME_END);
+};