Differentiate between different writes

[danbujak]

I have a few characteristics under a service, and I'm trying to store the value if any of these characteristics is written to. However I run into an issue where if I enable services on the Master Control Panel, my code thinks that the value of the characteristic is being written.

How do I differentiate between a write to the actual data value of my characteristic and whatever the master control panel is doing when I enable services?

static void ble_evt_dispatch(ble_evt_t * p_ble_evt)
{
    dm_ble_evt_handler(p_ble_evt);
    on_ble_evt(p_ble_evt);
    check_status(p_ble_evt);
}

static void check_status(ble_evt_t * p_ble_evt){	
    
    ble_gatts_evt_write_t *p_evt_write = &p_ble_evt -> evt.gatts_evt.params.write;
    
    switch (p_ble_evt -> header.evt_id)
        {
        case BLE_GATTS_EVT_WRITE:
            if (p_evt_write -> context.srvc_uuid.uuid == DEVICE_STATUS_SERVICE_UUID){
                /* If mode characteristic was written to update the status value */
                if (p_evt_write -> context.char_uuid.uuid == DEVICE_STATUS_MODE_UUID){
                    m_status.mode = p_evt_write -> data[0];
                }
                /* If datarate characteristic was written to update the status value */
                else if (p_evt_write -> context.char_uuid.uuid == DEVICE_STATUS_DATARATE_UUID){
                    m_status.datarate = p_evt_write -> data[0];
                }
                advertising_init();     /* Update advertising data with new mode and datarate */
            }
        break;
    }
}

Once I enable services, both m_status.mode and m_status.datarate are set to 0x03. If I write to both of these characteristics after enabling services the correct values are written to them. But for example if I only modify one, the other one will have 0x03 stored in it still (even though the attribute is storing 0x0).

[Petter Myhre]

You should be able use the GATT Server Attribute Types:

/** @defgroup BLE_GATTS_ATTR_TYPES GATT Server Attribute Types
 * @{ */
#define BLE_GATTS_ATTR_TYPE_INVALID         0x00  /**< Invalid Attribute Type. */
#define BLE_GATTS_ATTR_TYPE_PRIM_SRVC_DECL  0x01  /**< Primary Service Declaration. */
#define BLE_GATTS_ATTR_TYPE_SEC_SRVC_DECL   0x02  /**< Secondary Service Declaration. */
#define BLE_GATTS_ATTR_TYPE_INC_DECL        0x03  /**< Include Declaration. */
#define BLE_GATTS_ATTR_TYPE_CHAR_DECL       0x04  /**< Characteristic Declaration. */
#define BLE_GATTS_ATTR_TYPE_CHAR_VAL        0x05  /**< Characteristic Value. */
#define BLE_GATTS_ATTR_TYPE_DESC            0x06  /**< Descriptor. */
#define BLE_GATTS_ATTR_TYPE_OTHER           0x07  /**< Other, non-GATT specific type. */
/** @} */

When you get a write event check that the write is to the characteristic value, not the descriptor.

if(p_ble_evt->evt.gatts_evt.params.write.context.type == BLE_GATTS_ATTR_TYPE_CHAR_VAL)
{
      //Your code
}

[Tony Garland]

I'm working with s13x_nrf5x_2.0.0 and the migration document indicates that write.context has been replaced by write.uuid. The write.uuid has a type field, but that appears to be the type of UUID, not the GATT server attribute type. So, when working with the s132, how can one check that the write is to a characteristic value?