How long do pointers to characteristic data need to be valid?

RE: How long do pointers to characteristic data need to be valid?

Tim — Wed, 14 Oct 2015 12:58:50 GMT

Ah frames. I'd forgotten those existed!

RE: How long do pointers to characteristic data need to be valid?

Wojtek — Wed, 14 Oct 2015 12:56:23 GMT

To properly copy links from infocenter, right-click on the desired chapter in the content list on the left side and copy from there - link that you provided point to main page.

RE: How long do pointers to characteristic data need to be valid?

Tim — Wed, 14 Oct 2015 12:52:39 GMT

Ah found it here: infocenter.nordicsemi.com/.../structble__gatts__attr__t.html By the way the formatting seems a bit wrong on that page. I think it would be nice if the function documentation mention this, rather than just the documentation for the parameter structure.

RE: How long do pointers to characteristic data need to be valid?

Tim — Wed, 14 Oct 2015 12:50:12 GMT

I can't actually find that documentation snippet. It isn't here: infocenter.nordicsemi.com/.../group___b_l_e___g_a_t_t_s___f_u_n_c_t_i_o_n_s.html or here: infocenter.nordicsemi.com/.../structble__gatts__value__t.html

RE: How long do pointers to characteristic data need to be valid?

Ulrich Myhre — Wed, 14 Oct 2015 12:45:07 GMT

This is actually documented together with the API calls themselves.

For p_value of ble_gatts_attr_t (used in sd_ble_gatts_characteristic_add, your example) this is stated:

Pointer to the attribute data. Please note that if the @ref BLE_GATTS_VLOC_USER value location is selected in the attribute metadata, this will have to point to a buffer that remains valid through the lifetime of the attribute. This excludes usage of automatic variables that may go out of scope or any other temporary location. The stack may access that memory directly without the application's knowledge. For writable characteristics, this value must not be a location in flash memory.

Which means that the lifetime is defined based on ble_gatts_attr_md_t.vloc.

If there are any other places where our documentation is lacking this, then please give us a hint.

RE: How long do pointers to characteristic data need to be valid?

Wojtek — Wed, 14 Oct 2015 12:37:45 GMT

I think that depends of vloc parameter in ble_gatts_attr_md_t... some description may be found here