I have a question about configuration of charateristic value R/W permission.

RE: I have a question about configuration of charateristic value R/W permission.

JoonDong — Sun, 19 Mar 2017 02:22:06 GMT

Thank you always.

RE: I have a question about configuration of charateristic value R/W permission.

FormerMember — Fri, 17 Mar 2017 09:31:13 GMT

I have updated my answer.

RE: I have a question about configuration of charateristic value R/W permission.

JoonDong — Thu, 16 Mar 2017 14:10:23 GMT

Sorry.. I can't understand.. because I couldn't find out intersection about configuration between char_md and attr_md.

there are contents about R/W availability, descriptors and so on in char_md. And in attr_md, there are contents about R/W permission, authoration and so on in attr_md.

Could you explain in detail??

RE: I have a question about configuration of charateristic value R/W permission.

FormerMember — Tue, 14 Mar 2017 10:22:17 GMT

Yes, part of the security for a device can be to limit the read/write properties.

attr_md sets the actual properties for a characteristic (the actual accessibility). char_md sets the properties that will be found during service discovery. For the properties to be in conformance with the Bluetooth Spec, the attr_md properties and the char_md properties should be the same.

Update March 17th 2017:

When adding a characteristic, both characteristic metadata and attribute metatdata should be set. As stated in the documentation for the characteristic metatdata --> characteristic properties (ble_gatts_char_md_t --> ble_gatt_char_props_t), it is only the properties of the characteristic.

The attribute metadata (ble_gatts_attr_md_t) contains the actual permissions.

RE: I have a question about configuration of charateristic value R/W permission.

JoonDong — Sat, 11 Mar 2017 09:05:47 GMT

But should cccd be set to Write and Notify?

RE: I have a question about configuration of charateristic value R/W permission.

JoonDong — Sat, 11 Mar 2017 09:03:04 GMT

And I can't find out the setting about R/W availability of Characteristic's components(characteristic value attribute, cccd and so on.. )

does Characteristic's R/W availability automatically apply to Characteristic's components?

RE: I have a question about configuration of charateristic value R/W permission.

JoonDong — Sat, 11 Mar 2017 01:36:36 GMT

Finally, does it mean that R/W availability and R/W permission should be separated?

RE: I have a question about configuration of charateristic value R/W permission.

AmiguelS — Fri, 10 Mar 2017 17:42:25 GMT

You may find this tutorial useful, more specifically Step 2.F. The following code configures a characteristic to allow Read and Notify but reject Write.

void ble_add_char(){
    ...

    //Add Characteristics to stack
    ble_gatts_char_md_t char_md;

    memset(&char_md, 0, sizeof(char_md));
    char_md.char_props.write_wo_resp  = 0;
    char_md.char_props.write  = 0;
    char_md.char_props.read   = 1;
    char_md.char_props.notify = 1;

    ...

    //Add Characteristic to stack
    sd_ble_gatts_characteristic_add(service, &char_md, &attr_char_value, handle);
}