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--- projects:crazyflie:crtp [2013-02-22 07:24]
macke
+++ projects:crazyflie:crtp [2013-04-02 15:41]
arnaud [Layers]
@@ Line 22: / Line 22: @@
 CRTP is implemented in 3 layers:
-<code>
+<ditaa>
  +-----------------------+
  |   Application/ports   |
@@ Line 30: / Line 30: @@
  |       CRTP Link       |
  +-----------------------+
-</code>
+</ditaa>
   * **CRTP Link** is responsible for transferring the packets between the Crazyflie and the host. It will typically handles packet size and error detection.
@@ Line 56: / Line 56: @@
 ===== Serial port =====
-This is mostly for legacy support but has been used during development to log data at higher speeds. The support for using the serial port might be broken currently though.
+The serial port is configured in 115200 8N1. CRTP packets are sent and received asynchronously using the following packet format:
 <code>
+   6   5   4   3   2   1   0
++---+---+---+---+---+---+---+---+
+|             0xAA              |
++---+---+---+---+---+---+---+---+
+|             0xAA              |
++---+---+---+---+---+---+---+---+
+|      Port     |  Res  | Chan. |
++---+---+---+---+---+---+---+---+
+|         Packet length         |
++---+---+---+---+---+---+---+---+
+|            DATA 0             |
++---+---+---+---+---+---+---+---+
+:   :   :   :   :   :   :   :   :
++---+---+---+---+---+---+---+---+
+|            Cksum              |
++---+---+---+---+---+---+---+---+
 +--------+--------+--------+--------+--------+--....--+--------+
-|  0xAA  |  0xAA  | Header | Length | Data0  | Packet | CRC32  |
+|  0xAA  |  0xAA  | Header | Length | Data0  | Packet | Cksum  |
 +--------+--------+--------+--------+--------+--....--+--------+
 </code>
-^ **Field** ^ **Byte** ^     **Description**     ^
+^ **Field** ^ **Byte** ^ **Bit** ^     **Description**     ^
-|   Start   |    0-1   | Start token for synchronization (0xAAAA)  |
+|   Start   |    0-1   |   0-2   | Start token for synchronization (0xAAAA)  |
-|   Header  |     2    | The destination channel  |
+|   Header  |     2    |   0-1   | The destination channel  |
-|    Size   |     3    | The size of the packet |
+|    :::    |     2    |   2-3   | Reserved for the link layer |
-|    Data   |    4-34  | The data in the packet |
+|    :::    |     2    |   4-7   | The destination port  |
-|    CRC    |   35-36  | The CRC16 of the packet |
+|    Size   |     3    |         | Number of data byte |
+|    Data   |    4-..  |         | The data in the packet |
+|   Cksum   |  4+size  |         | Checksum. Sum of all the bytes, excluding //Start//, modulo 256. |

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