[Zigbee] ZCL: Discover Attributes Extended Command

[Pawel(embeddedsolutions.pl)]

Setup: 

nrf52840dk

NCS v2.4.1

Hi,

ZCL Discover Attributes Extended Command allows to get the attribute access type. Based on the Zigbee Cluster Library spec 2.5.23.1.5 section the second bit of Attribute access control field should indicate if the discovered attribute is reportable or not. 

In zcl_general_commands.c: zb_zcl_disc_attr_handler() following line of code is used for putting the attribute access type to the ZCL Discover Attributes Extended Response.

ZB_ZCL_PACKET_PUT_DATA8(resp_data, ZB_ZCL_CONVERT_ATTR_ACCESS_BITMASK(attr_desc->access));
 
/*! Convert internal attribute access bitmask into ZCL/HA1.2 bitmask
* value (actually, support 0 and 1 bits) */
#define ZB_ZCL_CONVERT_ATTR_ACCESS_BITMASK(_access) ((_access) & 0x3U)

It seems that only bit 0 and bit 1 of access field are being put into the packet.

zb_zcl_common.h introduces the bits for setting attribute access as follows: 

/**
* @name ZCL attribute access values
* @anchor zcl_attr_access
*/
/** @{ */
#define ZB_ZCL_ATTR_ACCESS_READ_ONLY 0x01U
#define ZB_ZCL_ATTR_ACCESS_WRITE_ONLY 0x02U /*!< Attribute is write only */
/** Attribute is read/write */
#define ZB_ZCL_ATTR_ACCESS_READ_WRITE (ZB_ZCL_ATTR_ACCESS_READ_ONLY | ZB_ZCL_ATTR_ACCESS_WRITE_ONLY)
#define ZB_ZCL_ATTR_ACCESS_REPORTING 0x04U /*!< Attribute is allowed for reporting */

ZB_ZCL_ATTR_ACCESS_REPORTING is the bit 2 in the attribute descriptor access, so it seems that it is not possible to determine if discovered attribute is reportable or not. 

Could you elaborate on that topic ? 

Please, correct me if I am wrong and point me to the right direction.

My goal is to be able to determine if discovered attribute is reportable or not.

[Marte Myrvold]

Hi,

I am currently investigating this.

In the meantime, have you tested sending a Discover Attributes Extended command to see if it the correct access is sent in the response?

Best regards,
Marte

[Pawel(embeddedsolutions.pl)]

Hi Marte,

Yes I have tested that and I receive access values in range <0x1, 0x3> so only 2 bits are taken into account.

Received access correctly reflects what I have defined at my ZED.

[Marte Myrvold]

Hi,

Thank you for verifying. I was also able to reproduce this in NCS v2.5.0 with the Light Bulb sample. I have reported it to the developers.

Best regards,
Marte

[Marte Myrvold]

Hi,

You can fix this by changing 0x3U to 0x7U in ZB_ZCL_CONVERT_ATTR_ACCESS_BITMASK:

#define ZB_ZCL_CONVERT_ATTR_ACCESS_BITMASK(_access) ((_access) & 0x7U)

I have tested that this works, but please verify it on your side as well.

Best regards,
Marte

[Pawel(embeddedsolutions.pl)]

Hi, thank you for fast response.

Will it be then compatible with the Zigbee spec ? 

Best regards,

Pawel

[Marte Myrvold]

Hi Pawel,

Yes, it should be compatible with the Zigbee spec.

Best regards,
Marte

[Pawel(embeddedsolutions.pl)]

Hi Marte,

Is it possible to make that small change without needing to do the fork ? 
Like undef the previous macro and set new corrected one ? 

Best regards,

Pawel

[Marte Myrvold]

Hi Pawel,

You need to define it in such a way that the discover attributes handler, zb_zcl_disc_attr_handler(), in zcl_general_commands.c gets the correct value. So you can either change it directly in zb_zcl_commands.h or redefine it in zcl_general_commands.c.

Best regards,
Marte

[Pawel(embeddedsolutions.pl)]

Hi Marte,

Are you going to fix that in the near future ? 

Best regards,

Pawel