[ESP8266] Adds support for controlling HW reset of the modem from the driver

While connecting will run HW reset for the modem if reset wire is attached to a know pin.

Author: Veijo Pesonen

components/wifi/esp8266-driver/ESP8266/ESP8266.cpp

@@ -91,9 +91,18 @@ ESP8266::ESP8266(PinName tx, PinName rx, bool debug, PinName rts, PinName cts)
 
 bool ESP8266::at_available()
 {
+    bool ready = false;
+
     _smutex.lock();
-    bool ready = _parser.send("AT")
-                 && _parser.recv("OK\n");
+    // Might take a while to respond after HW reset
+    for(int i = 0; i < 5; i++) {
+        ready = _parser.send("AT")
+                && _parser.recv("OK\n");
+        if (ready) {
+            break;
+        }
+        tr_debug("waiting AT response");
+    }
     _smutex.unlock();
 
     return ready;

components/wifi/esp8266-driver/ESP8266Interface.cpp

@@ -27,6 +27,7 @@
 #include "mbed_trace.h"
 #include "platform/Callback.h"
 #include "platform/mbed_debug.h"
+#include "platform/mbed_wait_api.h"
 
 #ifndef MBED_CONF_ESP8266_DEBUG
 #define MBED_CONF_ESP8266_DEBUG false
@@ -40,13 +41,18 @@
 #define MBED_CONF_ESP8266_CTS NC
 #endif
 
+#ifndef MBED_CONF_ESP8266_RST
+#define MBED_CONF_ESP8266_RST NC
+#endif
+
 #define TRACE_GROUP  "ESPI" // ESP8266 Interface
 
 using namespace mbed;
 
 #if defined MBED_CONF_ESP8266_TX && defined MBED_CONF_ESP8266_RX
 ESP8266Interface::ESP8266Interface()
     : _esp(MBED_CONF_ESP8266_TX, MBED_CONF_ESP8266_RX, MBED_CONF_ESP8266_DEBUG, MBED_CONF_ESP8266_RTS, MBED_CONF_ESP8266_CTS),
+      _rst_pin(MBED_CONF_ESP8266_RST), // Notice that Pin7 CH_EN cannot be left floating if used as reset
       _ap_sec(NSAPI_SECURITY_UNKNOWN),
       _initialized(false),
       _started(false),
@@ -71,8 +77,9 @@ ESP8266Interface::ESP8266Interface()
 #endif
 
 // ESP8266Interface implementation
-ESP8266Interface::ESP8266Interface(PinName tx, PinName rx, bool debug, PinName rts, PinName cts)
+ESP8266Interface::ESP8266Interface(PinName tx, PinName rx, bool debug, PinName rts, PinName cts, PinName rst)
     : _esp(tx, rx, debug, rts, cts),
+      _rst_pin(rst),
       _ap_sec(NSAPI_SECURITY_UNKNOWN),
       _initialized(false),
       _started(false),
@@ -102,6 +109,35 @@ ESP8266Interface::~ESP8266Interface()
     }
 }
 
+ESP8266Interface::ResetPin::ResetPin(PinName rst_pin) : _rst_pin(mbed::DigitalOut(rst_pin, 1))
+{
+}
+
+void ESP8266Interface::ResetPin::assert()
+{
+    if (_rst_pin.is_connected()) {
+        _rst_pin = 0;
+        // 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
+        wait_us(200);
+        tr_debug("HW reset asserted");
+    }
+}
+
+void ESP8266Interface::ResetPin::deassert()
+{
+    if (_rst_pin.is_connected()) {
+        // Notice that Pin7 CH_EN cannot be left floating if used as reset
+        _rst_pin = 1;
+        tr_debug("HW reset deasserted");
+    }
+}
+
+bool ESP8266Interface::ResetPin::is_connected()
+{
+    return _rst_pin.is_connected();
+}
+
 int ESP8266Interface::connect(const char *ssid, const char *pass, nsapi_security_t security,
                               uint8_t channel)
 {
@@ -224,6 +260,8 @@ int ESP8266Interface::set_channel(uint8_t channel)
 
 int ESP8266Interface::disconnect()
 {
+    _initialized = false;
+
     if (_conn_stat == NSAPI_STATUS_DISCONNECTED)
     {
         return NSAPI_ERROR_NO_CONNECTION;
@@ -313,6 +351,8 @@ bool ESP8266Interface::_get_firmware_ok()
 nsapi_error_t ESP8266Interface::_init(void)
 {
     if (!_initialized) {
+        _hw_reset();
+
         if (!_esp.at_available()) {
             return NSAPI_ERROR_DEVICE_ERROR;
         }
@@ -343,6 +383,12 @@ nsapi_error_t ESP8266Interface::_init(void)
     return NSAPI_ERROR_OK;
 }
 
+void ESP8266Interface::_hw_reset()
+{
+    _rst_pin.assert();
+    _rst_pin.deassert();
+}
+
 nsapi_error_t ESP8266Interface::_startup(const int8_t wifi_mode)
 {
     if (!_started) {

components/wifi/esp8266-driver/ESP8266Interface.h

@@ -18,6 +18,7 @@
 #define ESP8266_INTERFACE_H
 
 #if DEVICE_SERIAL && defined(MBED_CONF_EVENTS_PRESENT) && defined(MBED_CONF_NSAPI_PRESENT) && defined(MBED_CONF_RTOS_PRESENT)
+#include "drivers/DigitalOut.h"
 #include "ESP8266/ESP8266.h"
 #include "events/EventQueue.h"
 #include "events/mbed_shared_queues.h"
@@ -59,7 +60,7 @@ class ESP8266Interface : public NetworkStack, public WiFiInterface {
      * @param rx        RX pin
      * @param debug     Enable debugging
      */
-    ESP8266Interface(PinName tx, PinName rx, bool debug = false, PinName rts = NC, PinName cts = NC);
+    ESP8266Interface(PinName tx, PinName rx, bool debug = false, PinName rts = NC, PinName cts = NC, PinName rst = NC);
 
     /**
      * @brief ESP8266Interface default destructor
@@ -320,6 +321,18 @@ class ESP8266Interface : public NetworkStack, public WiFiInterface {
     ESP8266 _esp;
     void update_conn_state_cb();
 
+    // HW reset pin
+    class ResetPin {
+    public:
+        ResetPin(PinName rst_pin);
+        void assert();
+        void deassert();
+        bool is_connected();
+    private:
+        mbed::DigitalOut  _rst_pin;
+    } _rst_pin;
+
+
     // Credentials
     static const int ESP8266_SSID_MAX_LENGTH = 32; /* 32 is what 802.11 defines as longest possible name */
     char ap_ssid[ESP8266_SSID_MAX_LENGTH + 1]; /* The longest possible name; +1 for the \0 */
@@ -339,6 +352,7 @@ class ESP8266Interface : public NetworkStack, public WiFiInterface {
     int _initialized;
     bool _get_firmware_ok();
     nsapi_error_t _init(void);
+    void _hw_reset();
     int _started;
     nsapi_error_t _startup(const int8_t wifi_mode);
 

components/wifi/esp8266-driver/mbed_lib.json

@@ -17,6 +17,10 @@
             "help": "CTS pin for serial connection, defaults to Not Connected",
             "value": null
         },
+        "rst": {
+            "help": "RESET pin for the modem, defaults to Not Connected",
+            "value": null
+        },
         "debug": {
             "help": "Enable debug logs. [true/false]",
             "value": false