Cellular: Fix Non-IP of Quectel/BG96 modem driver

Add missing license headers.
Remove semaphores to allow async operation.
Change hex format to allow binary payload.
Limit payload size to 100 bytes.
Fix missing plus char at +QCFGEXT.

features/cellular/framework/AT/ATHandler.cpp

@@ -1637,7 +1637,7 @@ void ATHandler::set_send_delay(uint16_t send_delay)
     _at_send_delay = send_delay;
 }
 
-void ATHandler::write_hex_string(char *str, size_t size)
+void ATHandler::write_hex_string(const char *str, size_t size)
 {
     // do common checks before sending subparameter
     if (check_cmd_send() == false) {

features/cellular/framework/AT/ATHandler.h

@@ -433,7 +433,7 @@ public:
      *  @param str input buffer to be converted to hex ascii
      *  @param size of the input param str
      */
-    void write_hex_string(char *str, size_t size);
+    void write_hex_string(const char *str, size_t size);
 
     /** Reads as string and converts result to integer. Supports only non-negative integers.
      *

features/cellular/framework/targets/QUECTEL/BG96/QUECTEL_BG96_CellularContext.cpp

@@ -84,9 +84,13 @@ nsapi_error_t QUECTEL_BG96_CellularContext::activate_non_ip_context()
 
     // Open the NIDD connection
     nsapi_size_or_error_t ret = _at.at_cmd_discard("+QCFGEXT", "=\"nipd\",1");
-
     if (ret == NSAPI_ERROR_OK) {
-        _semaphore.try_acquire_for(NIDD_OPEN_URC_TIMEOUT);
+        _at.lock();
+        _at.set_at_timeout(NIDD_OPEN_URC_TIMEOUT);
+        _at.resp_start("+QIND:");
+        urc_nidd();
+        _at.restore_at_timeout();
+        _at.unlock();
         if (_cid == -1) {
             return NSAPI_ERROR_NO_CONNECTION;
         }
@@ -142,7 +146,6 @@ void QUECTEL_BG96_CellularContext::urc_nidd_open()
     } else {
         tr_error("NIDD connection open failed with error: %d", err);
     }
-    _semaphore.release();
 }
 
 void QUECTEL_BG96_CellularContext::urc_nidd_close()

features/cellular/framework/targets/QUECTEL/BG96/QUECTEL_BG96_CellularContext.h

@@ -37,7 +37,6 @@ protected:
     virtual void deactivate_non_ip_context();
     virtual void deactivate_context();
     virtual void activate_context();
-    rtos::Semaphore _semaphore;
 
 private:
     void urc_nidd();

features/cellular/framework/targets/QUECTEL/BG96/QUECTEL_BG96_ControlPlane_netif.cpp

@@ -1,4 +1,25 @@
+/*
+ * Copyright (c) 2018, Arm Limited and affiliates.
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "CellularUtil.h"
 #include "QUECTEL_BG96_ControlPlane_netif.h"
+#include "CellularLog.h"
+
+using namespace mbed_cellular_util;
 
 namespace mbed {
 
@@ -7,21 +28,26 @@ QUECTEL_BG96_ControlPlane_netif::QUECTEL_BG96_ControlPlane_netif(ATHandler &at,
 
 nsapi_size_or_error_t QUECTEL_BG96_ControlPlane_netif::send(const void *data, nsapi_size_t size)
 {
-    nsapi_size_or_error_t err = _at.at_cmd_discard("+QCFGEXT", "=\"nipds\",0,", "%s%d", data, size);
-
-    if (err == NSAPI_ERROR_OK) {
-        return size;
+    if (size > 100) { // from BG96_NIDD_AT_Commands_Manual_V1.0
+        return NSAPI_ERROR_PARAMETER;
     }
 
-    return err;
+    _at.lock();
+    _at.cmd_start("AT+QCFGEXT=\"nipds\",1,");
+    _at.write_hex_string((const char *)data, size);
+    _at.write_int(2 * size);
+    _at.cmd_stop_read_resp();
+    nsapi_error_t err = _at.unlock_return_error();
+
+    return (err == NSAPI_ERROR_OK) ? size : err;
 }
 
 nsapi_size_or_error_t QUECTEL_BG96_ControlPlane_netif::recv(void *buffer, nsapi_size_t size)
 {
     _at.lock();
 
-    _at.cmd_start_stop("QCFGEXT", "=", "%s%d", "nipdr", 0);
-    _at.resp_start("+QCFGEXT: ");
+    _at.cmd_start_stop("+QCFGEXT", "=", "%s%d", "nipdr", 0);
+    _at.resp_start("+QCFGEXT:");
     // skip 3 params: "nipdr",<total_receive_length>,<have_read_length>
     _at.skip_param(3);
     // get to <unread_length>
@@ -32,20 +58,22 @@ nsapi_size_or_error_t QUECTEL_BG96_ControlPlane_netif::recv(void *buffer, nsapi_
         _at.unlock();
         return NSAPI_ERROR_WOULD_BLOCK;
     }
+    if ((nsapi_size_t)unread_length > size) {
+        tr_warn("recv %d/%d", size, unread_length);
+        unread_length = size;
+    }
 
-    _at.cmd_start_stop("QCFGEXT", "=", "%s%d", "nipdr", unread_length);
-
+    _at.cmd_start_stop("+QCFGEXT", "=", "%s%d%d", "nipdr", unread_length, 1);
     _at.resp_start("+QCFGEXT:");
-    // skip "nipdr"
-    _at.skip_param();
-    int read_length = _at.read_int();
-    _at.read_string((char *)buffer, read_length);
+    _at.skip_param(); // skip "nipdr"
+    nsapi_size_t read_length = _at.read_int();
+    ssize_t read_len = _at.read_hex_string((char *)buffer, read_length);
     _at.resp_stop();
-    nsapi_error_t err = _at.get_last_error();
-    _at.unlock();
 
-    if (err == NSAPI_ERROR_OK && read_length) {
-        return read_length;
+    nsapi_error_t err = _at.unlock_return_error();
+
+    if (err == NSAPI_ERROR_OK && read_len) {
+        return read_len;
     }
 
     return NSAPI_ERROR_WOULD_BLOCK;