diff --git a/port/arduino/BTstack.h b/port/arduino/BTstack.h
index 75012f6aa..ccdac7ff6 100644
--- a/port/arduino/BTstack.h
+++ b/port/arduino/BTstack.h
@@ -1,7 +1,12 @@
 /**
  * Arduino Wrapper for BTstack
  */
-#pragma once
+#ifndef __ARDUINO_BTSTACK_H
+#define __ARDUINO_BTSTACK_H
+
+#if defined __cplusplus
+extern "C" {
+#endif
 
 #include "ble/att.h"
 #include "btstack_util.h" 
@@ -187,4 +192,10 @@ public:
  	uint16_t addGATTCharacteristicDynamic(UUID * uuid, uint16_t flags, uint16_t characteristic_id);
 };
 
- extern BTstackManager BTstack;
\ No newline at end of file
+extern BTstackManager BTstack;
+
+#if defined __cplusplus
+}
+#endif
+
+#endif // __ARDUINO_BTSTACK_H
\ No newline at end of file
diff --git a/port/libusb/main.c b/port/libusb/main.c
index a623813c3..d37051677 100644
--- a/port/libusb/main.c
+++ b/port/libusb/main.c
@@ -91,7 +91,7 @@ int main(int argc, const char * argv[]){
     hci_dump_open("/tmp/hci_dump.pklg", HCI_DUMP_PACKETLOGGER);
 
     // init HCI
-	cosnt hci_transport_t * transport = hci_transport_usb_instance();
+	const hci_transport_t * transport = hci_transport_usb_instance();
     remote_device_db_t * remote_db = (remote_device_db_t *) &remote_device_db_fs;
 	hci_init(transport, NULL, remote_db);
     
diff --git a/src/classic/rfcomm.c b/src/classic/rfcomm.c
index 2cd89b7ce..b504b8b3c 100644
--- a/src/classic/rfcomm.c
+++ b/src/classic/rfcomm.c
@@ -1924,6 +1924,10 @@ int rfcomm_send_prepared(uint16_t rfcomm_cid, uint16_t len){
 
     int err = rfcomm_assert_send_valid(channel, len);
     if (err) return err;
+    if (l2cap_can_send_prepared_packet_now(channel->multiplexer->l2cap_cid)){
+        log_error("rfcomm_send_prepared: l2cap cannot send now");
+        return BTSTACK_ACL_BUFFERS_FULL;
+    }
 
     // send might cause l2cap to emit new credits, update counters first
     channel->credits_outgoing--;
@@ -1932,10 +1936,10 @@ int rfcomm_send_prepared(uint16_t rfcomm_cid, uint16_t len){
     
     if (result != 0) {
         channel->credits_outgoing++;
-        log_info("rfcomm_send: error %d", result);
+        log_error("rfcomm_send_prepared: error %d", result);
         return result;
     }
-        
+    
     return result;
 }
 
@@ -1948,11 +1952,19 @@ int rfcomm_send(uint16_t rfcomm_cid, uint8_t *data, uint16_t len){
 
     int err = rfcomm_assert_send_valid(channel, len);
     if (err) return err;
+    if (l2cap_can_send_packet_now(channel->multiplexer->l2cap_cid)){
+        log_error("rfcomm_send_internal: l2cap cannot send now");
+        return BTSTACK_ACL_BUFFERS_FULL;
+    }
 
     rfcomm_reserve_packet_buffer();
     uint8_t * rfcomm_payload = rfcomm_get_outgoing_buffer();
     memcpy(rfcomm_payload, data, len);
-    return rfcomm_send_prepared(rfcomm_cid, len);    
+    err = rfcomm_send_prepared(rfcomm_cid, len);    
+    if (err){
+        rfcomm_release_packet_buffer();
+    }
+    return err;
 }
 
 // Sends Local Lnie Status, see LINE_STATUS_..
diff --git a/src/l2cap.c b/src/l2cap.c
index 8fb7b93f0..2c81b81ef 100644
--- a/src/l2cap.c
+++ b/src/l2cap.c
@@ -205,6 +205,12 @@ int  l2cap_can_send_packet_now(uint16_t local_cid){
     return hci_can_send_acl_packet_now(channel->handle);
 }
 
+int  l2cap_can_send_prepared_packet_now(uint16_t local_cid){
+    l2cap_channel_t *channel = l2cap_get_channel_for_local_cid(local_cid);
+    if (!channel) return 0;
+    return hci_can_send_prepared_acl_packet_now(channel->handle);
+}
+
 int  l2cap_can_send_fixed_channel_packet_now(uint16_t handle){
     return hci_can_send_acl_packet_now(handle);
 }
diff --git a/src/l2cap.h b/src/l2cap.h
index db064539f..d99307790 100644
--- a/src/l2cap.h
+++ b/src/l2cap.h
@@ -162,7 +162,7 @@ typedef struct l2cap_signaling_response {
 } l2cap_signaling_response_t;
     
 
-// internal use 
+
 int  l2cap_can_send_fixed_channel_packet_now(uint16_t handle);
 void l2cap_register_fixed_channel(btstack_packet_handler_t packet_handler, uint16_t channel_id);
 int  l2cap_send_connectionless(uint16_t handle, uint16_t cid, uint8_t *data, uint16_t len);
@@ -244,6 +244,7 @@ void l2cap_decline_connection(uint16_t local_cid, uint8_t reason);
  * @brief Check if outgoing buffer is available and that there's space on the Bluetooth module
  */
 int  l2cap_can_send_packet_now(uint16_t local_cid);    
+int  l2cap_can_send_prepared_packet_now(uint16_t local_cid);
 
 /** 
  * @brief Reserve outgoing buffer