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2017-08-26T22:52:13Z

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= CANOpen =

CANopen is a communication protocol and device profile specification for embedded systems used in automation.

* https://en.wikipedia.org/wiki/CANopen
* specifications https://www.can-cia.org/
* mirror http://overpof.free.fr/schneider/CAN%20&%20CANopen/CANopen/%A9CiA%20CANCANopen%20CD%20V5.1/index.htm

== Object dictionary ==

Object dictionary encapsulates all of the CAN exposed variables and allows reading or writing to
sections specified by index and subindex. All variables have types and complex types are allowed - records and arrays.

Two major parts of the object dictionary are defined - communication profile area in range ''0x1000-0x1FFF''
and application profile area (Standardised Device Profile Area) in range ''0x6000-0x9FFF''. Communication
profile parameters are used internally by CANOpen stack (e.g. heartbeat period, pdo parameters) while application profile area defines application
parameters (e.g. target velocity, control word).

* Specification is part of CiA 301

=== Layout ===

Object dictionary sections:

<pre>
0000 not used
0001-001F Static Data Types
0020-003F Complex Data Types
0040-005F Manufacturer Specific Complex Data Types
0060-007F Device Profile Specific Static Data Types
0080-009F Device Profile Specific Complex Data Types
00A0-0FFF Reserved for further use
1000-1FFF Communication Profile Area
2000-5FFF Manufacturer Specific Profile Area
6000-9FFF Standardised Device Profile Area
A000-BFFF Standardised Interface Profile Area
C000-FFFF Reserved for further use
</pre>

== NMT service ==

Network management services allows controlling node state transitions. Also provides heartbeat functionality.
On boot, CANOpen node automatically enters pre-operational NMT state, where node configuration usually takes place.
After configuration, node can be switched to operational state where PDO services are available. NMT also defines
initialising state, stopped state and two states for resetting object dictionary values - reset application
and reset communication for resetting respective parts of object dictionary.

* Specification is part of CiA 301

== SDO service ==

Allows reading or writing to variables in object dictionary. Device can implement multiple SDO services
but generally only one service (default SDO) is provided that allows object dictionary variable access.

SDO Upload -> Read register from device:

# rs-canopen-sdo-upload vcan0 05 6000 01

vcan0 605 [8] 40 00 60 01 00 00 00 00

SDO Download -> Write register to device:

# rs-canopen-sdo-download vcan0 05 6000 01 13

vcan0 605 [8] 2F 00 60 01 13 00 00 00

* Specification is part of CiA 301.
* COB-ID for default SDO tx (transmitted from node) - '''0x580 + node ID'''
* COB-ID for default SDO rx (received by node) - '''0x600 + node ID'''

== PDO ==

PDO or Process Data Objects allow communication without protocol overhead. PDO allows mapping of single or multiple variables
into one CAN message with specific ID. This allows usage of all 8 bytes of CAN message data and allows writing or reading
multiple variables at once.

There are two kinds of PDOs: transmit and receive PDOs (TPDO and RPDO). Transmit PDOs are used to read data from node
and receive PDOs are used for writes.

For example RPDO for servo controller can contain mapping to two variables - ''control word'' and ''target velocity''. Both of these
are 32 bit values

* ''control word'' unsigned int32 at address ''0x6040''
* ''target velocity'' signed int32 at address ''0x60FF''

This fills up full 8 bytes of CAN data.

In similar manner, TPDO can be used for monitoring the drive, example mapping can look like this:

* ''status word'' unsigned int32 at address ''0x6041''
* ''velocity actual'' signed int32 at address ''0x606C''

Specification is part of CiA 301.

== SYNC ==

Node synchronization is accomplished with the help of SYNC message. This can be used to either sample
current sensor values at SYNC time or apply buffered SDO data to all variables at once.

* Specification is part of CiA 301
* COB-ID used by SYNC message is '''0x80'''

== LSS ==

Layer Setting Services and Protocol allows configuration of node ID and CAN baudrate.
This protocol runs prior other CANOpen services as they require node ID to be configured.

Typically used when adding new nodes to the system. Non-configured node boots into LSS mode indicated
by both LEDs blinking rapidly. Node ID and baudrate can be configured and configuration stored in
non-volatile memory for next boots. If node ID is valid device skips LSS mode and goes straight into
pre-operational state.

* LSS is defined in CiA 305
* COB-ID used by NMT is '''0x0'''

CANOpen - Revision history

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