Add data_length_update to BLE DFU (#293)

* Add data length update for ble dfu

Data length update needs to be called explicitly in SD v5, it's not automatically adjusted with ATT MTU exchange as in SD v3

* Update required version for pc_ble_driver_py

Need pc_ble_driver_py 0.14.1 to get data_length_update feature

Author: bihanssen

nordicsemi/dfu/dfu_transport_ble.py

@@ -47,7 +47,7 @@
 from pc_ble_driver_py.exceptions    import NordicSemiException, IllegalStateException
 from pc_ble_driver_py.ble_driver    import BLEDriver, BLEDriverObserver, BLEEnableParams, BLEUUIDBase, BLEGapSecKDist, BLEGapSecParams, \
     BLEGapIOCaps, BLEUUID, BLEAdvData, BLEGapConnParams, NordicSemiErrorCheck, BLEGapSecStatus, driver
-from pc_ble_driver_py.ble_driver    import ATT_MTU_DEFAULT, BLEConfig, BLEConfigConnGatt
+from pc_ble_driver_py.ble_driver    import ATT_MTU_DEFAULT, BLEConfig, BLEConfigConnGatt, BLEConfigConnGap
 from pc_ble_driver_py.ble_adapter   import BLEAdapter, BLEAdapterObserver, EvtSync
 
 logger  = logging.getLogger(__name__)
@@ -120,6 +120,9 @@ def open(self):
                 BLEConfig.conn_gatt,
                 BLEConfigConnGatt(att_mtu=DFUAdapter.LOCAL_ATT_MTU),
             )
+            self.adapter.driver.ble_cfg_set(
+                BLEConfig.conn_gap,
+                BLEConfigConnGap(event_length=5))  # Event length 5 is required for max data length
             self.adapter.driver.ble_enable()
 
         self.adapter.driver.ble_vs_uuid_add(DFUAdapter.BASE_UUID)
@@ -168,6 +171,13 @@ def connect(self, target_device_name, target_device_addr):
             if DFUAdapter.LOCAL_ATT_MTU > ATT_MTU_DEFAULT:
                 logger.info('BLE: Enabling longer ATT MTUs')
                 self.att_mtu = self.adapter.att_mtu_exchange(self.conn_handle, DFUAdapter.LOCAL_ATT_MTU)
+
+                logger.info('BLE: Enabling longer Data Length')
+                max_data_length = 251  # Max data length for SD v5
+                data_length = self.att_mtu + 4  # ATT PDU overhead is 4
+                if data_length > max_data_length:
+                    data_length = max_data_length
+                self.adapter.data_length_update(self.conn_handle, data_length)
             else:
                 logger.info('BLE: Using default ATT MTU')
 

requirements-frozen.txt

@@ -5,7 +5,7 @@ ecdsa==0.13.3
 intelhex==2.2.1
 ipaddress==1.0.22
 libusb1==1.7.1
-pc-ble-driver-py==0.14.0
+pc-ble-driver-py==0.14.1
 piccata==2.0.1
 protobuf==3.10.0
 pyserial==3.4

requirements.txt

@@ -4,7 +4,7 @@ crcmod
 ecdsa
 intelhex
 libusb1
-pc_ble_driver_py >= 0.14.0
+pc_ble_driver_py >= 0.14.1
 piccata
 protobuf
 pyserial