Add get_time function to Wifi interface and ESP8266

get_time function allows access to SNTP functionalities of WiFi modules.
ESP8266 is the first module to offer this function in mbed-os.

Author: michalpasztamobica

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

@@ -1084,6 +1084,65 @@ void ESP8266::attach(Callback<void()> status_cb)
     _conn_stat_cb = status_cb;
 }
 
+bool ESP8266::set_sntp_config(bool enable, int timezone, const char *server0,
+                              const char *server1, const char *server2)
+{
+    bool done = false;
+    _smutex.lock();
+    if ((server0 == nullptr || server0[0] == '\0')) {
+        done = _parser.send("AT+CIPSNTPCFG=%d,%d",
+                            enable ? 1 : 0, timezone);
+    } else if ((server0 != nullptr || server0[0] != '\0')
+               && (server1 == nullptr && server1[0] == '\0')) {
+        done = _parser.send("AT+CIPSNTPCFG=%d,%d,%s",
+                            enable ? 1 : 0, timezone, server0);
+    } else if ((server0 != nullptr || server0[0] != '\0')
+               && (server1 != nullptr && server1[0] != '\0')
+               && (server2 == nullptr && server2[0] == '\0')) {
+        done = _parser.send("AT+CIPSNTPCFG=%d,%d,%s,%s",
+                            enable ? 1 : 0, timezone, server0, server1);
+    } else {
+        done = _parser.send("AT+CIPSNTPCFG=%d,%d,%s,%s,%s",
+                            enable ? 1 : 0, timezone, server0, server1, server2);
+    }
+    done &= _parser.recv("OK\n");
+    _smutex.unlock();
+    return done;
+}
+
+bool ESP8266::get_sntp_config(bool *enable, int *timezone, char *server0,
+                              char *server1, char *server2)
+{
+    _smutex.lock();
+    unsigned int tmp;
+    bool done = _parser.send("AT+CIPSNTPCFG?")
+                && _parser.scanf("+CIPSNTPCFG:%d,%d,\"%32[^\"]\",\"%32[^\"]\",\"%32[^\"]\"",
+                                 &tmp, timezone, server0, server1, server2)
+                && _parser.recv("OK\n");
+    _smutex.unlock();
+    *enable = tmp ? true : false;
+    return done;
+}
+
+bool ESP8266::get_sntp_time(std::tm *t)
+{
+    _smutex.lock();
+    char buf[25]; // Thu Aug 04 14:48:05 2016 (always 24 chars + \0)
+    memset(buf, 0, 25);
+    bool done = _parser.send("AT+CIPSNTPTIME?")
+                && _parser.scanf("+CIPSNTPTIME:%24c", &buf)
+                && _parser.recv("OK\n");
+    _smutex.unlock();
+
+    std::istringstream ss(buf);
+    ss >> std::get_time(t, "%a %b %d %H:%M:%S %Y");
+    if (ss.fail()) {
+        return false;
+    } else {
+        return true;
+    }
+}
+
 bool ESP8266::_recv_ap(nsapi_wifi_ap_t *ap)
 {
     int sec = NSAPI_SECURITY_UNKNOWN;

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

@@ -19,6 +19,8 @@
 
 #if DEVICE_SERIAL && DEVICE_INTERRUPTIN && defined(MBED_CONF_EVENTS_PRESENT) && defined(MBED_CONF_NSAPI_PRESENT) && defined(MBED_CONF_RTOS_API_PRESENT)
 #include <stdint.h>
+#include <sstream>
+#include <iomanip>
 
 #include "drivers/BufferedSerial.h"
 #include "features/netsocket/nsapi_types.h"
@@ -334,6 +336,47 @@ class ESP8266 {
     */
     void attach(mbed::Callback<void()> status_cb);
 
+    /**
+     * Configure SNTP (Simple Network Time Protocol)
+     *
+     * @param enable   true to enable SNTP or false to disable it
+     * @param timezone timezone offset [-11,13] (0 by default)
+     * @param server0  optional parameter indicating the first SNTP server ("cn.ntp.org.cn" by default)
+     * @param server1  optional parameter indicating the second SNTP server ("ntp.sjtu.edu.cn" by default)
+     * @param server2  optional parameter indicating the third SNTP server ("us.pool.ntp.org" by default)
+     *
+     * @retval true if successful, false otherwise
+     */
+    bool set_sntp_config(bool enable, int timezone = 0, const char *server0 = nullptr,
+                         const char *server1 = nullptr, const char *server2 = nullptr);
+
+    /**
+     * Read out the configuration of SNTP (Simple Network Time Protocol)
+     *
+     * @param enable   true if SNTP is enabled
+     * @param timezone timezone offset [-11,13]
+     * @param server0  name of the first SNTP server
+     * @param server1  name of the second SNTP server (optional, nullptr if not set)
+     * @param server2  name of the third SNTP server (optional, nullptr if not set)
+     *
+     * @retval true if successful, false otherwise
+     */
+    bool get_sntp_config(bool *enable, int *timezone, char *server0,
+                         char *server1, char *server2);
+
+    /**
+     * Read out SNTP time from ESP8266.
+     *
+     * @param t std::tm structure to be filled in
+     * @retval true on success, false otherwise
+     *
+     * @note ESP8266 must be connected and needs a couple of seconds
+     * before returning correct time. It may return 1 Jan 1970 if it is not ready.
+     *
+     * @note esp8266.sntp-enable must be set to true in mbed_app.json file.
+     */
+    bool get_sntp_time(std::tm *t);
+
     template <typename T, typename M>
     void attach(T *obj, M method)
     {

components/wifi/esp8266-driver/ESP8266Interface.cpp

@@ -596,6 +596,12 @@ const char *ESP8266Interface::get_netmask()
     return _conn_stat != NSAPI_STATUS_DISCONNECTED ? _esp.netmask() : NULL;
 }
 
+nsapi_error_t ESP8266Interface::get_time(std::tm *t)
+{
+    _init();
+    return _esp.get_sntp_time(t) ? NSAPI_ERROR_OK : NSAPI_ERROR_TIMEOUT;
+}
+
 char *ESP8266Interface::get_interface_name(char *interface_name)
 {
     memcpy(interface_name, ESP8266_WIFI_IF_NAME, sizeof(ESP8266_WIFI_IF_NAME));
@@ -722,7 +728,13 @@ nsapi_error_t ESP8266Interface::_init(void)
         if (!_esp.startup(ESP8266::WIFIMODE_STATION)) {
             return NSAPI_ERROR_DEVICE_ERROR;
         }
-
+        if (!_esp.set_sntp_config(MBED_CONF_ESP8266_SNTP_ENABLE,
+                                  MBED_CONF_ESP8266_SNTP_TIMEZONE,
+                                  MBED_CONF_ESP8266_SNTP_SERVER0,
+                                  MBED_CONF_ESP8266_SNTP_SERVER1,
+                                  MBED_CONF_ESP8266_SNTP_SERVER2)) {
+            return NSAPI_ERROR_DEVICE_ERROR;
+        }
         _initialized = true;
     }
     return NSAPI_ERROR_OK;

components/wifi/esp8266-driver/ESP8266Interface.h

@@ -169,6 +169,12 @@ class ESP8266Interface : public NetworkStack, public WiFiInterface {
     MBED_DEPRECATED_SINCE("mbed-os-5.15", "String-based APIs are deprecated")
     virtual const char *get_netmask();
 
+    /** @copydoc WiFiInterface::get_time
+     *
+     *  @note esp8266.sntp-enable must be set to true in mbed_app.json.
+     */
+    virtual nsapi_error_t get_time(std::tm *t);
+
     /** Get the network interface name
      *
      *  @return         Null-terminated representation of the network interface name

components/wifi/esp8266-driver/mbed_lib.json

@@ -59,16 +59,36 @@
             "value": null
         },
         "channel-start": {
-            "help": "the channel number to start at, 1 by default",
+            "help": "The channel number to start at, 1 by default",
             "value": null
         },
         "channels": {
-            "help": "channel count, 13 by default",
+            "help": "Channel count, 13 by default",
             "value": null
         },
         "built-in-dns": {
             "help": "use built-in CIPDOMAIN AT command to resolve address to IP",
             "value": false
+        },
+        "sntp-enable": {
+            "help": "Enable SNTP. This allows application to use get_sntp_time()",
+            "value": false
+        },
+        "sntp-timezone": {
+            "help": "SNTP timezone",
+            "value": 0
+        },
+        "sntp-server0": {
+            "help": "First SNTP server. Empty string will let ESP8266 use its default.",
+            "value": "\"\""
+        },
+        "sntp-server1": {
+            "help": "Second SNTP server. Empty string will let ESP8266 use its default.",
+            "value": "\"\""
+        },
+        "sntp-server2": {
+            "help": "Third SNTP server. Empty string will let ESP8266 use its default.",
+            "value": "\"\""
         }
     },
     "target_overrides": {

features/netsocket/WiFiInterface.h

@@ -23,6 +23,7 @@
 #define WIFI_INTERFACE_H
 
 #include <string.h>
+#include <ctime>
 #include "netsocket/NetworkInterface.h"
 #include "netsocket/WiFiAccessPoint.h"
 
@@ -65,6 +66,16 @@ class WiFiInterface: public virtual NetworkInterface {
      */
     virtual int8_t get_rssi() = 0;
 
+    /** Get the current time.
+     *
+     * @retval          NSAPI_ERROR_UNSUPPORTED if the function is not supported
+     * @retval          NSAPI_ERROR_OK on success
+     */
+    virtual nsapi_error_t get_time(std::tm *t)
+    {
+        return NSAPI_ERROR_UNSUPPORTED;
+    }
+
     /** Attempt to connect to a Wi-Fi network.
      *
      *  @param ssid      Name of the network to connect to.