Diff: xbee.cpp

Revision:

5:6532c5a5f576

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/xbee.cpp	Wed Mar 23 14:32:41 2016 +0000
@@ -0,0 +1,113 @@
+#include <string.h>
+#include "xbee.h"
+
+
+int XBee::Receive(unsigned char *inBuff, int len, unsigned char *outBuff){
+    int unescapeLen = 0;
+    unsigned char checksum = 0;
+    unsigned char LSB = 0;
+
+    if (inBuff[0] != 0x7E)
+        return 0;
+
+    if (len < 10)
+        return 0;
+
+    unescapeLen = unescape(inBuff, len, outBuff);
+
+    // Check we have at least the amount of bytes indicated by LSB
+    LSB = outBuff[2]; 
+    if (LSB > (unescapeLen - 4))
+        return 0;
+
+    // Calculate our checksum
+    // (char will overflow, no need to AND for lower bytes)
+    for (int i=3; i<LSB+4; i++){
+        checksum += outBuff[i];
+    }
+
+    if (checksum != 0xFF)
+        return 0;
+
+    return LSB+4;
+}
+
+
+int XBee::Send(unsigned char *msg, int len, unsigned char *outBuff, const uint64_t addr){
+    unsigned char buf[len + 15];
+    int escapedLen = 0;
+    unsigned char checksum = 0;
+
+    buf[0] = 0x7E;
+    buf[1] = (len + 11) >> 8;
+    buf[2] = len + 11;
+    buf[3] = 0x00;  // transmit request
+    buf[4] = 0x00;  // Frame ID
+    buf[5] = addr >> 56;
+    buf[6] = addr >> 48;
+    buf[7] = addr >> 40;
+    buf[8] = addr >> 32;
+    buf[9] = addr >> 24;
+    buf[10] = addr >> 16;
+    buf[11] = addr >> 8;
+    buf[12] = addr;
+    buf[13] = 0x01;  // Disable acknowledge
+    memcpy(&buf[14], msg, len);
+
+    for (int i=3;i<len+14;i++){
+        checksum += buf[i];
+    }
+
+    buf[len+14] = 0xFF - checksum;
+    escapedLen = escape(buf, len+15, outBuff);
+
+    return escapedLen;
+}
+
+int XBee::escape(unsigned char *input, int inLen, unsigned char *output){
+    int pos = 1;
+
+    output[0] = input[0];
+    for (int i=1; i<inLen; i++){
+        switch(input[i]){
+            case 0x7D:
+            case 0x7E:
+            case 0x11:
+            case 0x13:
+                output[pos++] = 0x7D;
+                output[pos++] = input[i] ^ 0x20;
+                break;
+            default:
+                output[pos++] = input[i];
+                break;
+      }
+   }
+
+   return pos;
+}
+
+int XBee::unescape(unsigned char *input, int inLen, unsigned char *output){
+    int pos = 1;
+    bool skip = false;
+    unsigned char curr = 0;
+
+    output[0] = input[0];
+    for (int i=1; i<inLen; i++) {
+        if (skip){
+            skip = false;
+            continue;
+        }
+
+        if (input[i] == 0x7D){
+            curr = input[i+1] ^ 0x20;
+            skip = true;
+        }else{
+            curr = input[i];
+        }
+
+        output[pos] = curr;
+        pos++;
+    }
+
+    return pos;
+}
\ No newline at end of file