Posted on October 09, 2015 at 12:31Hello,
we have to transfer long attributes (images) on BlueTooth.
We read in BLE Specifications 4.0 that this can be accomplished
using the
“Write Long Characteristic Values�? procedure described in 4.9.4 of part F:
a sequence of Attribute Protocol
Prepare Write Request – Prepare Write Response
terminated by:
Execute Write Request - Execute Write Response
However, looking at the code, it seems that only BlueNRG MS (and not BlueNRG)
provides the offset:
#define EVT_BLUE_GATT_ATTRIBUTE_MODIFIED (0x0C01)
typedef __packed struct _evt_gatt_attr_modified{
uint16_t conn_handle; /**< The connection handle which modified the attribute. */
uint16_t attr_handle; /**< Handle of the attribute that was modified. */
uint8_t data_length; /**< The length of the data */
#if BLUENRG_MS
///@cond BLUENRG_MS
uint16_t offset; /**< Offset from which the write has been performed by the peer device */
///@endcond
#endif
uint8_t att_data[VARIABLE_SIZE]; /**< The new value (length is data_length) */
} PACKED evt_gatt_attr_modified;
What happens when a prepare write is received by the BlueNRG?
Is EVT_BLUE_GATT_ATTRIBUTE_MODIFIED event generated or is command rejected?
Does evt_gatt_attr_modified contain at least length and data?
I also wonder why an uint8_t (max value = 255) is used for data_length,
as in“
BlueTooth_Core_v4.0 “ Volume 3 of Part F – Attribute Protocol (ATT)
section 3.2.9 ''Long Attribute Values'' I read:
“
The maximum length of an attribute value shall be 512 octets.�?
Thanks
