MTU exchange

Author: rdnt

adapter_nrf528xx-full.go

@@ -17,6 +17,12 @@ import (
 	"unsafe"
 )
 
+// TODO: @rdnt cleanup
+//var (
+//	dataLenParams     = &C.ble_gap_data_length_params_t{}
+//	dataLenLimitation = &C.ble_gap_data_length_limitation_t{}
+//)
+
 func handleEvent() {
 	id := eventBuf.header.evt_id
 	switch {
@@ -63,7 +69,7 @@ func handleEvent() {
 				// because it would need to be reconfigured as a non-connectable
 				// advertisement. That's left as a future addition, if
 				// necessary.
-				C.sd_ble_gap_adv_start(defaultAdvertisement.handle, C.BLE_CONN_CFG_TAG_DEFAULT)
+				C.sd_ble_gap_adv_start(defaultAdvertisement.handle, connCfgTag)
 			}
 			device := Device{
 				connectionHandle: gapEvent.conn_handle,
@@ -159,7 +165,16 @@ func handleEvent() {
 		case C.BLE_GATTS_EVT_EXCHANGE_MTU_REQUEST:
 			// This event is generated by some devices. While we could support
 			// larger MTUs, this default MTU is supported everywhere.
-			C.sd_ble_gatts_exchange_mtu_reply(gattsEvent.conn_handle, C.BLE_GATT_ATT_MTU_DEFAULT)
+			rsp := gattsEvent.params.unionfield_exchange_mtu_request()
+			effectiveMtu := min(DefaultAdapter.cfg.Gatt.AttMtu, uint16(rsp.client_rx_mtu))
+			if debug {
+				println("mtu exchange requested. self:", DefaultAdapter.cfg.Gatt.AttMtu, ", peer:", rsp.client_rx_mtu, ", effective:", effectiveMtu)
+			}
+
+			var errCode = C.sd_ble_gatts_exchange_mtu_reply(gattsEvent.conn_handle, C.uint16_t(effectiveMtu))
+			if debug {
+				println("mtu exchange replied, err:", Error(errCode).Error())
+			}
 		case C.BLE_GATTS_EVT_HVN_TX_COMPLETE:
 			// ignore confirmation of a notification successfully sent
 		default:
@@ -255,6 +270,12 @@ func handleEvent() {
 					}
 				}
 			}
+
+		case C.BLE_GATTC_EVT_EXCHANGE_MTU_RSP:
+			if debug {
+				rsp := gattcEvent.params.unionfield_exchange_mtu_rsp()
+				println("mtu exchanged, effective mtu:", rsp.server_rx_mtu)
+			}
 		default:
 			if debug {
 				println("unknown GATTC event:", id, id-C.BLE_GATTC_EVT_BASE)
@@ -266,3 +287,10 @@ func handleEvent() {
 		}
 	}
 }
+
+func min(a, b uint16) uint16 {
+	if a < b {
+		return a
+	}
+	return b
+}

adapter_nrf528xx-peripheral.go

@@ -47,7 +47,7 @@ func handleEvent() {
 				// because it would need to be reconfigured as a non-connectable
 				// advertisement. That's left as a future addition, if
 				// necessary.
-				C.sd_ble_gap_adv_start(defaultAdvertisement.handle, C.BLE_CONN_CFG_TAG_DEFAULT)
+				C.sd_ble_gap_adv_start(defaultAdvertisement.handle, connCfgTag)
 			}
 			device := Device{
 				connectionHandle: gapEvent.conn_handle,

adapter_nrf528xx.go

@@ -31,6 +31,8 @@ var clockConfigXtal C.nrf_clock_lf_cfg_t = C.nrf_clock_lf_cfg_t{
 	accuracy:     C.NRF_CLOCK_LF_ACCURACY_250_PPM,
 }
 
+const connCfgTag uint8 = 1
+
 //go:extern __app_ram_base
 var appRAMBase [0]uint32
 
@@ -47,6 +49,41 @@ func (a *Adapter) enable() error {
 
 	// Enable the BLE stack.
 	appRAMBase := C.uint32_t(uintptr(unsafe.Pointer(&appRAMBase)))
+
+	bleCfg := C.ble_cfg_t{}
+
+	connCfg := bleCfg.unionfield_conn_cfg()
+	connCfg.conn_cfg_tag = connCfgTag
+
+	gattCfg := connCfg.params.unionfield_gatt_conn_cfg()
+	gattCfg.att_mtu = a.cfg.Gatt.AttMtu
+
+	errCode = C.sd_ble_cfg_set(C.uint32_t(C.BLE_CONN_CFG_GATT), &bleCfg, appRAMBase)
+	if debug {
+		println("gatt config updated, err:", Error(errCode).Error())
+	}
+
+	l2capCfg := connCfg.params.unionfield_l2cap_conn_cfg()
+	l2capCfg.rx_mps = a.cfg.L2cap.RxMps
+	l2capCfg.tx_mps = a.cfg.L2cap.TxMps
+	l2capCfg.rx_queue_size = a.cfg.L2cap.RxQueueSize
+	l2capCfg.tx_queue_size = a.cfg.L2cap.TxQueueSize
+	l2capCfg.ch_count = a.cfg.L2cap.ChCount // TODO: @rdnt max 18? 20 crashes
+
+	errCode = C.sd_ble_cfg_set(C.uint32_t(C.BLE_CONN_CFG_L2CAP), &bleCfg, appRAMBase)
+	if debug {
+		println("l2cap config updated, err:", Error(errCode).Error())
+	}
+
+	gapCfg := connCfg.params.unionfield_gap_conn_cfg()
+	gapCfg.conn_count = a.cfg.Gapp.ConnCount
+	gapCfg.event_length = a.cfg.Gapp.EventLength
+
+	errCode = C.sd_ble_cfg_set(C.uint32_t(C.BLE_CONN_CFG_GAP), &bleCfg, appRAMBase)
+	if debug {
+		println("gap config updated, err:", Error(errCode).Error())
+	}
+
 	errCode = C.sd_ble_enable(&appRAMBase)
 	return makeError(errCode)
 }

adapter_sd.go

@@ -33,7 +33,7 @@ var currentConnection = volatileHandle{handle: volatile.Register16{C.BLE_CONN_HA
 // Globally allocated buffer for incoming SoftDevice events.
 var eventBuf struct {
 	C.ble_evt_t
-	buf [23]byte
+	buf [247]byte
 }
 
 func init() {
@@ -49,6 +49,8 @@ type Adapter struct {
 	charWriteHandlers []charWriteHandler
 
 	connectHandler func(device Device, connected bool)
+
+	cfg Config
 }
 
 // DefaultAdapter is the default adapter on the current system. On Nordic chips,
@@ -62,6 +64,39 @@ var DefaultAdapter = &Adapter{isDefault: true,
 
 var eventBufLen C.uint16_t
 
+type Config struct {
+	Gapp  GapConfig
+	Gatt  GattConfig
+	L2cap L2capConfig
+}
+
+type GapConfig struct {
+	ConnCount   uint8
+	EventLength uint16
+}
+
+type GattConfig struct {
+	AttMtu uint16
+}
+
+type L2capConfig struct {
+	RxMps       uint16
+	TxMps       uint16
+	RxQueueSize uint8
+	TxQueueSize uint8
+	ChCount     uint8
+}
+
+func (a *Adapter) Configure(cfg Config) error {
+	if cfg.Gatt.AttMtu < 23 || cfg.Gatt.AttMtu > 247 {
+		cfg.Gatt.AttMtu = 23
+	}
+
+	a.cfg = cfg
+
+	return nil
+}
+
 // Enable configures the BLE stack. It must be called before any
 // Bluetooth-related calls (unless otherwise indicated).
 func (a *Adapter) Enable() error {
@@ -75,6 +110,10 @@ func (a *Adapter) Enable() error {
 			eventBufLen = C.uint16_t(unsafe.Sizeof(eventBuf))
 			errCode := C.sd_ble_evt_get((*C.uint8_t)(unsafe.Pointer(&eventBuf)), &eventBufLen)
 			if errCode != 0 {
+				// TODO: @rdnt remove
+				//if debug {
+				//	println("sd_ble_evt_get failed, err:", Error(errCode).Error())
+				//}
 				// Possible error conditions:
 				//  * NRF_ERROR_NOT_FOUND: no events left, break
 				//  * NRF_ERROR_DATA_SIZE: retry with a bigger data buffer

gap_nrf528xx-advertisement.go

@@ -74,7 +74,7 @@ func (a *Advertisement) Configure(options AdvertisementOptions) error {
 // Start advertisement. May only be called after it has been configured.
 func (a *Advertisement) Start() error {
 	a.isAdvertising.Set(1)
-	errCode := C.sd_ble_gap_adv_start(a.handle, C.BLE_CONN_CFG_TAG_DEFAULT)
+	errCode := C.sd_ble_gap_adv_start(a.handle, connCfgTag)
 	return makeError(errCode)
 }
 

gap_nrf528xx-central.go

@@ -12,6 +12,7 @@ import (
 
 /*
 #include "ble_gap.h"
+#include "ble_gattc.h"
 */
 import "C"
 
@@ -162,7 +163,7 @@ func (a *Adapter) Connect(address Address, params ConnectionParams) (Device, err
 	connectionAttempt.state.Set(1)
 
 	// Start the connection attempt. We'll get a signal in the event handler.
-	errCode := C.sd_ble_gap_connect(&addr, &scanParams, &connectionParams, C.BLE_CONN_CFG_TAG_DEFAULT)
+	errCode := C.sd_ble_gap_connect(&addr, &scanParams, &connectionParams, connCfgTag)
 	if errCode != 0 {
 		connectionAttempt.state.Set(0)
 		return Device{}, Error(errCode)
@@ -175,6 +176,12 @@ func (a *Adapter) Connect(address Address, params ConnectionParams) (Device, err
 			// Successfully connected.
 			connectionAttempt.state.Set(0)
 			connectionHandle := connectionAttempt.connectionHandle
+
+			errCode = C.sd_ble_gattc_exchange_mtu_request(connectionHandle, C.uint16_t(a.cfg.Gatt.AttMtu))
+			if debug {
+				println("mtu requested, self:", a.cfg.Gatt.AttMtu, " err:", Error(errCode).Error())
+			}
+
 			return Device{
 				connectionHandle: connectionHandle,
 			}, nil

gatts_sd.go

@@ -63,7 +63,7 @@ func (a *Adapter) AddService(service *Service) error {
 			},
 			init_len:  C.uint16_t(len(char.Value)),
 			init_offs: 0,
-			max_len:   20, // This is a conservative maximum length.
+			max_len:   C.BLE_GATTS_FIX_ATTR_LEN_MAX,
 		}
 		if len(char.Value) != 0 {
 			value.p_value = (*C.uint8_t)(unsafe.Pointer(&char.Value[0]))