fix length

readme.md

@@ -2,10 +2,12 @@
 # Simple wrapper for DataFrame
 
 Create formatted frame from basic types:
- - uint8_t, int8_t
- - uint16_t, int16_t
- - uint32_t, int32_t
- - float
+ - uint8_t, int8_t => 1Byte
+ - uint16_t, int16_t => 2Bytes
+ - uint32_t, int32_t => 4Bytes
+ - float => 4Bytes
+
+ Data are stared in Little Endian format.
 
 Structure of data frame:
   - starting byte (0xCC)
@@ -25,10 +27,13 @@ Structure of data frame:
     packet_create(data, 128);
 
     packet_add_uint8(0xAB);
-    packet_add_uint16(0xABCD);
+    packet_add_uint16(65874);
+    packet_add_int16(-45874);
     packet_add_uint32(0x12345678);
+    packet_add_int32(-0xA2345678);
     
     packet_add_float(0.265);
+    packet_add_float(-3.1415);
 
     int data_length = packet_commit();
     }

src/dataframe.c

@@ -167,8 +167,8 @@ uint8_t packet_add_float(float f)
 uint8_t packet_commit()
 {
 	// compute CRC
-	packet[length] = crc8(0, length-2, &(*(packet+2)));
-	packet[1] = length - 1;
+	packet[length--] = crc8(0, length-2, &(*(packet+2)));
+	packet[1] = length;
 	// length of payload: from byte 2 to CRC byte (the last)
 	return length;