weak hook preinit() #2111 #2133 #2136

cores/esp8266/Arduino.h

@@ -219,6 +219,7 @@ uint8_t shiftIn(uint8_t dataPin, uint8_t clockPin, uint8_t bitOrder);
 void attachInterrupt(uint8_t pin, void (*)(void), int mode);
 void detachInterrupt(uint8_t pin);
 
+void preinit(void);
 void setup(void);
 void loop(void);
 

cores/esp8266/core_esp8266_main.cpp

@@ -63,7 +63,7 @@ static uint32_t s_micros_at_task_start;
 
 extern "C" {
 extern const uint32_t __attribute__((section(".ver_number"))) core_version = ARDUINO_ESP8266_GIT_VER;
-const char* core_release = 
+const char* core_release =
 #ifdef ARDUINO_ESP8266_RELEASE
     ARDUINO_ESP8266_RELEASE;
 #else
@@ -243,18 +243,26 @@ extern "C" void ICACHE_RAM_ATTR app_entry (void)
     return app_entry_custom();
 }
 
+extern "C" void preinit (void) __attribute__((weak));
+extern "C" void preinit (void)
+{
+    /* do nothing by default */
+}
+
 extern "C" void user_init(void) {
     struct rst_info *rtc_info_ptr = system_get_rst_info();
     memcpy((void *) &resetInfo, (void *) rtc_info_ptr, sizeof(resetInfo));
 
     uart_div_modify(0, UART_CLK_FREQ / (115200));
 
-    init();
+    init(); // in core_esp8266_wiring.c, inits hw regs and sdk timer
 
     initVariant();
 
     cont_init(g_pcont);
 
+    preinit(); // Prior to C++ Dynamic Init (not related to above init() ). Meant to be user redefinable.
+
     ets_task(loop_task,
         LOOP_TASK_PRIORITY, s_loop_queue,
         LOOP_QUEUE_SIZE);

libraries/ESP8266WiFi/examples/EarlyDisableWiFi/EarlyDisableWiFi.ino

@@ -0,0 +1,58 @@
+
+#include <ESP8266WiFi.h>
+
+#ifndef STASSID
+#define STASSID "your-ssid"
+#define STAPSK  "your-password"
+#endif
+
+// preinit() is called before system startup
+// from nonos-sdk's user entry point user_init()
+
+void preinit() {
+  // Global WiFi constructors are not called yet
+  // (global class instances like WiFi, Serial... are not yet initialized)..
+  // No global object methods or C++ exceptions can be called in here!
+  //The below is a static class method, which is similar to a function, so it's ok.
+  ESP8266WiFiClass::preinitWiFiOff();
+}
+
+void setup() {
+  Serial.begin(115200);
+  Serial.setDebugOutput(true);
+  Serial.println("sleeping 5s");
+
+  // during this period, a simple amp meter shows
+  // an average of 20mA with a Wemos D1 mini
+  // a DSO is needed to check #2111
+  delay(5000);
+
+  Serial.println("waking WiFi up, sleeping 5s");
+  WiFi.forceSleepWake();
+
+  // amp meter raises to 75mA
+  delay(5000);
+
+  Serial.println("connecting to AP " STASSID);
+  WiFi.mode(WIFI_STA);
+  WiFi.begin(STASSID, STAPSK);
+
+  for (bool configured = false; !configured;) {
+    for (auto addr : addrList)
+      if ((configured = !addr.isLocal() && addr.ifnumber() == STATION_IF)) {
+        Serial.printf("STA: IF='%s' hostname='%s' addr= %s\n",
+                      addr.ifname().c_str(),
+                      addr.ifhostname(),
+                      addr.toString().c_str());
+        break;
+      }
+    Serial.print('.');
+    delay(500);
+  }
+
+  // amp meter cycles within 75-80 mA
+
+}
+
+void loop() {
+}

libraries/ESP8266WiFi/src/ESP8266WiFiGeneric.cpp

@@ -579,4 +579,25 @@ void wifi_dns_found_callback(const char *name, CONST ip_addr_t *ipaddr, void *ca
     esp_schedule(); // resume the hostByName function
 }
 
-
+//meant to be called from user-defined preinit()
+void ESP8266WiFiGenericClass::preinitWiFiOff () {
+  // https://github.com/esp8266/Arduino/issues/2111#issuecomment-224251391
+  // WiFi.persistent(false);
+  // WiFi.mode(WIFI_OFF);
+  // WiFi.forceSleepBegin();
+
+  //WiFi.mode(WIFI_OFF) equivalent:
+  // datasheet:
+  // Set Wi-Fi working mode to Station mode, SoftAP
+  // or Station + SoftAP, and do not update flash
+  // (not persistent)
+  wifi_set_opmode_current(WIFI_OFF);
+
+  //WiFi.forceSleepBegin(/*default*/0) equivalent:
+  // sleep forever until wifi_fpm_do_wakeup() is called
+  wifi_fpm_set_sleep_type(MODEM_SLEEP_T);
+  wifi_fpm_open();
+  wifi_fpm_do_sleep(0xFFFFFFF);
+
+  // use WiFi.forceSleepWake() to wake WiFi up
+}

libraries/ESP8266WiFi/src/ESP8266WiFiGeneric.h

@@ -88,6 +88,8 @@ class ESP8266WiFiGenericClass {
         bool forceSleepBegin(uint32 sleepUs = 0);
         bool forceSleepWake();
 
+        static void preinitWiFiOff (); //meant to be called in user-defined preinit()
+
     protected:
         static bool _persistent;
         static WiFiMode_t _forceSleepLastMode;