OVMS3/OVMS.V3/components/canopen/docs/Howto-detect-CANopen-nodes.rst

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How to detect and identify CANopen nodes
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So you've got a CAN bus with some devices, but you don't know which of them
speaks "CANopen", if any? The OVMS v3 will help you to detect them and open
their CANs ;)
Before you begin
----------------
…you need to activate the CAN bus(es) you're going to use. As a CANopen master
needs to write to the network, you need to start the interfaces in active mode,
i.e. …::
OVMS# can can1 start active 500000
OVMS# can can2 start active 125000
… and then start the CANopen master for the bus(es), i.e.::
OVMS# copen can1 start
OVMS# copen can2 start
Detecting CANopen nodes
-----------------------
The "open" in "CANopen" means any implementation can decide how much of the
standard it implements. There are some few mandatory features though, a CANopen
slave has to implement, if it wants to comply with the standard.
The mandatory features helping to detect and identify CANopen nodes on a CAN
bus are:
- NMT (network management), especially RESET and PREOP
- NMT bootup event messages
- Standard SDO access in pre-operational mode
If you've got CANopen nodes on a bus, even silent ones, issuing ``copen … nmt reset``
will tell all of them to reboot, and as bootup messages are mandatory,
you will see them in the OVMS log output like this::
I (162904) canopen: can1 node 1 new state: Booting
The OVMS CANopen master continously monitors the network for NMT and EMCY
messages. After bootup of all nodes, you can get a list of all nodes that have
been detected by issuing ``metrics list co.``::
OVMS# metrics list co.
co.can1.nd1.emcy.code
co.can1.nd1.emcy.type
co.can1.nd1.state Operational
.. note:: if you request a reset, nodes may decide to boot into pre-operational
state. That may produce some error messages. Don't worry, you can resolve this
anytime by issuing ``copen … nmt start``.
Identifying CANopen nodes
-------------------------
In pre-operational state, a CANopen node must be accessible at the CANopen
default IDs. That means if the node supports SDO access, we can query some
standard attributes from it.
That's what ``copen … info`` and ``copen … scan`` do:
- ``copen … info`` queries the standard device attributes from a specific node,
- ``copen … scan`` queries all 127 node IDs.
.. caution:: There may be non-CANopen devices on the bus producing regular data
frames at CANopen response IDs and/or reading and possibly misinterpreting
CANopen requests sent to node IDs not planned by the manufacturer. Chances are
low this triggers problems, but you should be ready to switch off the vehicle
when doing a scan -- just in case.
A complete scan takes about 20 seconds. A typical scan could look like this::
OVMS# level debug canopen
OVMS# copen can1 scan
Scan #1-127...
Node #1:
Device type: 0x00000000
Error state: 0x00
Vendor ID: 0x0000001e
Product: 0x0712302d
Revision: 0x00010019
S/N: 0x47c5…………
Device name: Gen4 (Renault Twizy)11 November 2011 12
HW version: 0x00000003
SW version: 0712.0001
Node #23: SDO access failed
Node #25: SDO access failed
Node #27: SDO access failed
Node #30: SDO access failed
Node #87: SDO access failed
Done.
D (227994) canopen: ReadSDO #23 0x1000.00: InitUpload failed, CANopen error code 0xffffffff
D (228194) canopen: ReadSDO #25 0x1000.00: InitUpload failed, CANopen error code 0xffffffff
D (228444) canopen: ReadSDO #27 0x1000.00: InitUpload failed, CANopen error code 0xffffffff
D (228844) canopen: ReadSDO #30 0x1000.00: InitUpload failed, CANopen error code 0xffffffff
D (238384) canopen: ReadSDO #87 0x1000.00: InitUpload failed, CANopen error code 0xffffffff
This means one CANopen node was found, and some non-CANopen frames were
received on IDs 0x580 +23, +25, +27, +30 and +87.
Great! What now?
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As you now know there's a CANopen node, you can look for documentation on it.
You can also try to access more default SDOs to see if you can control and
configure the node.
* If you're lucky, the device will provide its own EDS file at SDO 1021.00. You
can check that by issuing…::
OVMS# copen <bus> readsdo <nodeid> 1021 0
* Check out the `CiA specifications <https://www.can-cia.org/standardization/specifications/>`_,
for CANopen standards, for example…
- DS301 for details on general standard SDOs
- DS401 for the generic I/O device class definition
- DS402 for motor controller SDOs
* Look up the manufacturer of your device by it's vendor ID:
https://www.can-cia.org/services/canopen-vendor-id/
* Contact the manufacturer of your device for specific documentation and EDS files.