Cellular: Added write_hex_string to AT handler

Author: Mirela Chirica

features/cellular/framework/AT/ATHandler.cpp

@@ -1597,3 +1597,18 @@ void ATHandler::set_send_delay(uint16_t send_delay)
 {
     _at_send_delay = send_delay;
 }
+
+void ATHandler::write_hex_string(char *str, size_t size)
+{
+    // do common checks before sending subparameter
+    if (check_cmd_send() == false) {
+        return;
+    }
+
+    char hexbuf[2];
+    for (int i = 0; i < size; i++) {
+        hexbuf[0] = hex_values[((str[i]) >> 4) & 0x0F];
+        hexbuf[1] = hex_values[(str[i]) & 0x0F];
+        write(hexbuf, 2);
+    }
+}

features/cellular/framework/AT/ATHandler.h

@@ -419,6 +419,14 @@ class ATHandler {
      */
     ssize_t read_hex_string(char *str, size_t size);
 
+    /** Converts contained chars to their hex ascii value and writes the resulting string to the file handle
+     *  For example: "AV" to "4156".
+     *
+     *  @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);
+
     /** Reads as string and converts result to integer. Supports only non-negative integers.
      *
      *  @return the non-negative integer or -1 in case of error.

features/cellular/framework/targets/QUECTEL/BC95/QUECTEL_BC95_CellularStack.cpp

@@ -185,11 +185,6 @@ nsapi_size_or_error_t QUECTEL_BC95_CellularStack::socket_sendto_impl(CellularSoc
         return NSAPI_ERROR_PARAMETER;
     }
 
-    char *hexstr = new char[size * 2 + 1];
-    int hexlen = char_str_to_hex_str((const char *)data, size, hexstr);
-    // NULL terminated for write_string
-    hexstr[hexlen] = 0;
-
     if (socket->proto == NSAPI_UDP) {
         _at.cmd_start("AT+NSOST=");
         _at.write_int(socket->id);
@@ -201,20 +196,17 @@ nsapi_size_or_error_t QUECTEL_BC95_CellularStack::socket_sendto_impl(CellularSoc
         _at.write_int(socket->id);
         _at.write_int(size);
     } else {
-        delete [] hexstr;
         return NSAPI_ERROR_PARAMETER;
     }
 
-    _at.write_string(hexstr, false);
+    _at.write_hex_string((char *)data, size);
     _at.cmd_stop();
     _at.resp_start();
     // skip socket id
     _at.skip_param();
     sent_len = _at.read_int();
     _at.resp_stop();
 
-    delete [] hexstr;
-
     if (_at.get_last_error() == NSAPI_ERROR_OK) {
         return sent_len;
     }