ESP8266: Add configuration for reset assert time

Author: ccli8

components/wifi/esp8266-driver/ESP8266Interface.cpp

@@ -461,7 +461,7 @@ nsapi_error_t ESP8266Interface::_reset()
         _rst_pin.rst_assert();
         // If you happen to use Pin7 CH_EN as reset pin, not needed otherwise
         // https://www.espressif.com/sites/default/files/documentation/esp8266_hardware_design_guidelines_en.pdf
-        ThisThread::sleep_for(2); // Documentation says 200 us; need 2 ticks to get minimum 1 ms.
+        ThisThread::sleep_for(MBED_CONF_ESP8266_RST_ASSERT_TIME_US / 1000); // Documentation says 200 us; need 2 ticks to get minimum 1 ms.
         _esp.flush();
         _rst_pin.rst_deassert();
     } else {

components/wifi/esp8266-driver/mbed_lib.json

@@ -26,6 +26,10 @@
             "options": [0, 1],
             "value": 0
         },
+        "rst-assert-time-us": {
+            "help": "Assert time of reset for the modem in us.",
+            "value": 2000
+        },
         "debug": {
             "help": "Enable debug logs. [true/false]",
             "value": false