studying Matter

[jhc]

Hi,

I am learning Matter. I have some questions:

1. Where can I get the resources, especially official resources, to study Matter?
2. What is the use of the Service discovery in Matter? Is there any service implemented in Matter itself?
3. What is the relationship and difference between the Access Control cluster and the Binding cluster in Endpoint 0?
4. Is the Subscription function implemented by Binding through the Binging cluster?
5. Does the Binding process have to be carried out by the Admin node?
6. Does the Admin of the network have a default permission to access the ACL of other Matter devices?

Thanks in advance for any help.

[Jørgen Holmefjord]

Hi,

Where can I get the resources, especially official resources, to study Matter?

To get access to the Matter specification, you should become a member of the Connectivity Standard Alliance (CSA). You can find the available documentation from Nordic in the nRF Connect SDK documentation:

• Matter
• Matter Documentation

What is the use of the Service discovery in Matter? Is there any service implemented in Matter itself?

The Matter specification defines supported clusters, which representation of a single functionality within a Matter device, such as turning a device on and off. Each cluster contains attributes, commands, and events, which can be mandatory or optional.

• What is the relationship and difference between the Access Control cluster and the Binding cluster in Endpoint 0?
• Is the Subscription function implemented by Binding through the Binging cluster?
• Does the Binding process have to be carried out by the Admin node?
• Does the Admin of the network have a default permission to access the ACL of other Matter devices?

I will have to check with our Matter team regarding these questions.

Best regards,
Jørgen

[Jørgen Holmefjord]

Hi,

Here are the answers to the rest of your questions from our Matter team:

3. They are completely unrelated clusters. Access Control cluster is used to grant privileges for accessing or configuring a given aspect of a node while Binding cluster is used to bind a client cluster on a node with a specific server cluster on another node (or group of nodes). A typical use case for the latter is binding a light switch to act upon a specific lighting device.

4.No, subscription is a general mechanism of the Matter's Interaction Model. Many attributes and events from different clusters can be subscribed to and Binding cluster is not involved in that process.

5. Description of each cluster in the specification includes the "Access" column that states what privilege level is needed to read or write a given attribute or run a given command. From that you can conclude that to read bindings you need to have a View privilege, and to modify it - Manage privilege.

6. The commissioner has by default Administer privilege level on all nodes it has commissioned.

Best regards,
Jørgen

[jhc]

Hi, 

Thanks for your reply!

for 3. As known, the Attribute of Binding Cluster is a list of binding targets, like below, SWITCH binds with BULB, so a binding target would be added to the binding list of the SWITCH:

Should an ACL item be added to the list of Access Control Cluster of the BULB to grant the SWITCH the corresponding permission (maybe Operate Privilege) ?

logo

[Jørgen Holmefjord]

Yes, in such a setup (each) light bulb device needs to be provided with proper ACL which defines that this particular light switch (in given fabric, with given node ID) is allowed to control defined clusters. In general this is done with Matter controller, like chip-tool, which by default has admin privilege. This is described in light_switch docs:

https://developer.nordicsemi.com/nRF_Connect_SDK/doc/2.0.0/nrf/samples/matter/light_switch/README.html

i.e.:

chip-tool accesscontrol write acl '[{"fabricIndex": 1, "privilege": 5, "authMode": 2, "subjects": [112233], "targets": null}, {"fabricIndex": 1, "privilege": 3, "authMode": 2, "subjects": [<light_switch_node_ID>], "targets": [{"cluster": 6, "endpoint": 1, "deviceType": null}, {"cluster": 8, "endpoint": 1, "deviceType": null}]}]' <light_bulb_node_ID> 0

will allow the light switch to manipulate clusters 6 and 8 (on/off and brightness) on the light bulb with provided node ID.