Bug fix in setting data rate

Setting up user defined data rate was found broken maybe because of
some rebase issue. Code has been setting always the default data rate
and ignoring used defined values.

Author: Hasnain Virk

features/lorawan/LoRaWANStack.cpp

@@ -332,7 +332,7 @@ lora_mac_status_t LoRaWANStack::send_frame_to_mac()
 {
     lora_mac_mcps_req_t mcps_req;
     lora_mac_status_t status;
-   // LoRaMacTxInfo_t txInfo;
+    lora_mac_mib_request_confirm_t mib_get_params;
 
     GetPhyParams_t phy_params;
     PhyParam_t default_datarate;
@@ -353,7 +353,14 @@ lora_mac_status_t LoRaWANStack::send_frame_to_mac()
         mcps_req.f_buffer = _tx_msg.f_buffer;
         mcps_req.f_buffer_size = _tx_msg.f_buffer_size;
         mcps_req.req.confirmed.nb_trials = _tx_msg.message_u.confirmed.nb_trials;
-        mcps_req.req.confirmed.datarate = default_datarate.Value;
+
+        mib_get_params.type = LORA_MIB_CHANNELS_DATARATE;
+           if(mib_get_request(&mib_get_params) != LORA_MAC_STATUS_OK) {
+               tr_debug("Couldn't get MIB parameters: Using default data rate");
+               mcps_req.req.confirmed.datarate = default_datarate.Value;
+           } else {
+               mcps_req.req.confirmed.datarate = mib_get_params.param.channels_datarate;
+           }
 
     } else if (LORA_MCPS_PROPRIETARY == mcps_req.type) {
         mcps_req.f_buffer = _tx_msg.f_buffer;