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--- doc:crazyflie:crtp:param [2014-11-25 16:17]
macke created
+++ doc:crazyflie:crtp:param [2020-05-12 14:22] (current)
kimberly
@@ Line 1: / Line 1: @@
+<WRAP center round important 60%>
+This page has deprecated and moved to the new documentation framework of the main Bitcraze website. Please go to [[https://www.bitcraze.io/documentation/system/]]
+</WRAP>
+====== Parameters ======
+The parameters system makes all the gettable and settable parameters of the copter accessible. The copter holds a table of parameters which can be retrieved. In this table every parameter name is associated with an ID and a group name. Three IDs are used to acces the TOC and the parameters:
+^  Port  ^  Channel  ^ Function          ^
+|  2     |  0        | [[doc:crazyflie:crtp:param#toc_access|TOC access]]        |
+|  2     |  1        | [[doc:crazyflie:crtp:param#parameter_read|Parameter read]]    |
+|  2     |  2        | [[doc:crazyflie:crtp:param#parameter_write|Parameter write]]   |
+|  2     |  3        | [[doc:crazyflie:crtp:param#misc_command|Misc. commands]]    |
+===== TOC access =====
+These messages permit to access the parameters table of content. The first byte of the message is a message ID, three messages ID are defined:
+^  Message ID  ^  Meaning in upstream packets  ^  Meaning in downstream packets      ^
+|            0 | Reset TOC pointer             | Last TOC element                    |
+|            1 | Get next TOC element          | TOC element (ID, type, group, name) |
+|            3 | Get TOC CRC32                 | Number of parameters, TOC CRC32     |
+The upstream ID are commands and are sent alone. The downstream has the following formats:
+<code>
+Bytes     1       1          1    Null terminated strings
+        +---+------------+------+----------+--------------+
+        | 0 |            |      |          |              |
+        +---+  Param ID  | Type |  Group   |     Name     |
+        | 1 |            |      |          |              |
+        +---+------------+------+---+------+--------------+
+        | 3 | Num. Param |  CRC32   |
+        +---+------------+----------+
+Bytes     1       1           4
+</code>
+The parameters are sequentially requested by the PC until the end. When the last parameter is reached it has the ID 0 'Last TOC element'. The reset command permits to reset the TOC pointers so that the next sent TOC element will be the first one. The "Get TOC CRC" command also returns the number of parameters.
+The CRC32 is a hash of the copter TOC. This is aimed at implementing caching of the TOC in the PC Utils to avoid fetching the full TOC each time the copter is connected.
+The type is one byte describing the parameter type:
+^ Type code ^ C type ^ Python unpack |
+| 0x08      | uint8_t | '<B' |
+| 0x09      | uint16_t | '<H' |
+| 0x0A      | uint32_t | '<L' |
+| 0x0B      | uint64_t | '<Q' |
+| 0x00      | int8_t | '<b' |
+| 0x01      | int16_t | '<h' |
+| 0x02      | int32_t | '<i' |
+| 0x03      | int64_t | '<q' |
+| 0x05      | FP16 | '' |
+| 0x06      | float | '<f' |
+| 0x07      | double | '<d' |
+===== Parameter read =====
+<WRAP group>
+<WRAP half column>
+^ Byte ^ Request fields ^ Content  ^
+|  0   | ID       | ID of the parameter to read (see TOC) |
+</WRAP>
+<WRAP half column>
+^ Byte ^ Answer fields  ^ Content  ^
+|  0   | ID       | ID of the parameter |
+|  1-..  | value | Value of the parameter. Size and format is described in the TOC |
+</WRAP>
+</WRAP>
+The read request is a simple packet on channel 1. Crazyflie answers with the value.
+===== Parameter write =====
+<WRAP group>
+<WRAP half column>
+^ Byte ^ Request fields ^ Content  ^
+|  0   | ID       | ID of the parameter to write |
+|  1-...   | value | Value to write. Size and format is described in the TOC |
+</WRAP>
+<WRAP half column>
+^ Byte ^ Answer fields  ^ Content  ^
+|  0   | ID       | ID of the parameter |
+|  1-...  | value | Value of the parameter. Size and format is described in the TOC |
+</WRAP>
+</WRAP>
+The write request is a simple packet on channel 2. Crazyflie sends back the parameter value as an acknowledgement.
+===== Misc. commands =====
+The following misc commands are implemented:
+^  Code  ^ Command ^
+|  0x00  | [[doc:crazyflie:crtp:param#set_by_name|Set by name]] |
+==== Set by name ====
+<WRAP group>
+<WRAP half column>
+^ Byte ^ Request fields ^ Content  ^
+|  0   | SET_BY_NAME       | 0x00 |
+|  1-n   | group | Name of the group |
+|  n-(n+1)  | NULL | 0 |
+|  (n+1)-(n+m+1)   | name | Name of the parameter |
+|  (n+m+1)-(n+m+2)  | NULL | 0 |
+|  (n+m+2)-(n+m+3)  | TYPE | Parameter type |
+|  (n+m+3)-...      | value | Value. Size and format is described by type |
+</WRAP>
+<WRAP half column>
+^ Byte ^ Answer fields  ^ Content  ^
+|  0   | SET_BY_NAME       | 0x00 |
+|  1-n   | group | Name of the group |
+|  n-(n+1)  | NULL | 0 |
+|  (n+1)-(n+m+1)   | name | Name of the parameter |
+|  (n+m+2)  | NULL | 0 |
+|  (n+m+3)  | ERROR | 0 if the parameter has been successfully written. Other code are taken from[[http://www.virtsync.com/c-error-codes-include-errno|errno C codes]]. |
+</WRAP>
+</WRAP>
+//Group// and //name// are ascii strings of size respectively //n// and //m//. The type corresponds to the TOC type of the parameter. It is checked for consistency.
+This command is useful to set a parameter without having to fetch the full TOC. It is enough to know the group, name and type of the parameter to write it.

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