lorawan: store current datarate for ADR

Keep track of the current network datarate when ADR is enabled.

The datarate can change in two circumstances. Firstly, the datarate may
change as a result of a command from the LoRaWAN server as the link
budget varies. Secondly, the datarate may be changed due to not
receiving an expected ADRACKReq response. This necessitates querying the
datarate on both packet reception and transmission to provide timely
notifications to the application.

Due to querying the default region datarate at startup and validating
manual datarate parameters, when ADR is not enabled the datarate will
never be different from the value provided to `lorawan_set_datarate`.

Signed-off-by: Jordan Yates <[email protected]>

Author: Jordan Yates

subsys/lorawan/lorawan.c

@@ -53,7 +53,12 @@ K_SEM_DEFINE(mcps_confirm_sem, 0, 1);
 K_MUTEX_DEFINE(lorawan_join_mutex);
 K_MUTEX_DEFINE(lorawan_send_mutex);
 
-static enum lorawan_datarate lorawan_datarate;
+/* We store both the default datarate requested through lorawan_set_datarate
+ * and the current datarate so that we can use the default datarate for all
+ * join requests, even as the current datarate changes due to ADR.
+ */
+static enum lorawan_datarate default_datarate;
+static enum lorawan_datarate current_datarate;
 static uint8_t lorawan_conf_msg_tries = 1;
 static bool lorawan_adr_enable;
 
@@ -83,6 +88,20 @@ static void OnMacProcessNotify(void)
 	LoRaMacProcess();
 }
 
+static void datarate_observe(bool force_notification)
+{
+	MibRequestConfirm_t mibGet;
+
+	mibGet.Type = MIB_CHANNELS_DATARATE;
+	LoRaMacMibGetRequestConfirm(&mibGet);
+
+	if ((mibGet.Param.ChannelsDatarate != current_datarate) ||
+	    (force_notification)) {
+		current_datarate = mibGet.Param.ChannelsDatarate;
+		LOG_INF("Datarate changed: DR_%d", current_datarate);
+	}
+}
+
 static void McpsConfirm(McpsConfirm_t *mcpsConfirm)
 {
 	LOG_DBG("Received McpsConfirm (for McpsRequest %d)",
@@ -95,6 +114,11 @@ static void McpsConfirm(McpsConfirm_t *mcpsConfirm)
 		LOG_DBG("McpsRequest success!");
 	}
 
+	/* Datarate may have changed due to a missed ADRACK */
+	if (lorawan_adr_enable) {
+		datarate_observe(false);
+	}
+
 	last_mcps_confirm_status = mcpsConfirm->Status;
 	/* mcps_confirm_sem is only blocked on in the MCPS_CONFIRMED case */
 	if (mcpsConfirm->McpsRequest == MCPS_CONFIRMED) {
@@ -112,6 +136,11 @@ static void McpsIndication(McpsIndication_t *mcpsIndication)
 		return;
 	}
 
+	/* Datarate can change as result of ADR command from server */
+	if (lorawan_adr_enable) {
+		datarate_observe(false);
+	}
+
 	/* TODO: Check MCPS Indication type */
 	if (mcpsIndication->RxData == true) {
 		if (mcpsIndication->BufferSize != 0) {
@@ -170,7 +199,7 @@ static LoRaMacStatus_t lorawan_join_otaa(
 	MibRequestConfirm_t mib_req;
 
 	mlme_req.Type = MLME_JOIN;
-	mlme_req.Req.Join.Datarate = lorawan_datarate;
+	mlme_req.Req.Join.Datarate = default_datarate;
 
 	mib_req.Type = MIB_DEV_EUI;
 	mib_req.Param.DevEui = join_cfg->dev_eui;
@@ -290,7 +319,7 @@ int lorawan_join(const struct lorawan_join_config *join_cfg)
 		MibRequestConfirm_t mib_req;
 
 		mib_req.Type = MIB_CHANNELS_DATARATE;
-		mib_req.Param.ChannelsDatarate = lorawan_datarate;
+		mib_req.Param.ChannelsDatarate = default_datarate;
 		LoRaMacMibSetRequestConfirm(&mib_req);
 	}
 
@@ -344,7 +373,8 @@ int lorawan_set_datarate(enum lorawan_datarate dr)
 		return -EINVAL;
 	}
 
-	lorawan_datarate = dr;
+	default_datarate = dr;
+	current_datarate = dr;
 
 	return 0;
 }
@@ -429,14 +459,14 @@ int lorawan_send(uint8_t port, uint8_t *data, uint8_t len, uint8_t flags)
 			mcpsReq.Req.Confirmed.fBuffer = data;
 			mcpsReq.Req.Confirmed.fBufferSize = len;
 			mcpsReq.Req.Confirmed.NbTrials = lorawan_conf_msg_tries;
-			mcpsReq.Req.Confirmed.Datarate = lorawan_datarate;
+			mcpsReq.Req.Confirmed.Datarate = current_datarate;
 		} else {
 			/* default message type */
 			mcpsReq.Type = MCPS_UNCONFIRMED;
 			mcpsReq.Req.Unconfirmed.fPort = port;
 			mcpsReq.Req.Unconfirmed.fBuffer = data;
 			mcpsReq.Req.Unconfirmed.fBufferSize = len;
-			mcpsReq.Req.Unconfirmed.Datarate = lorawan_datarate;
+			mcpsReq.Req.Unconfirmed.Datarate = current_datarate;
 		}
 	}
 
@@ -503,7 +533,8 @@ int lorawan_start(void)
 	/* Retrieve the default TX datarate for selected region */
 	phy_params.Attribute = PHY_DEF_TX_DR;
 	phy_param = RegionGetPhyParam(LORAWAN_REGION, &phy_params);
-	lorawan_datarate = phy_param.Value;
+	default_datarate = phy_param.Value;
+	current_datarate = default_datarate;
 
 	/* TODO: Move these to a proper location */
 	mib_req.Type = MIB_SYSTEM_MAX_RX_ERROR;