Initial support for CPU frequency selection

Author: igrr

hardware/esp8266com/esp8266/boards.txt

@@ -1,5 +1,5 @@
 menu.UploadSpeed=Upload Speed
-
+menu.CpuFrequency=CPU Frequency
 ##############################################################
 esp01.name=Generic ESP8266 board
 
@@ -17,6 +17,12 @@ esp01.build.board=ESP8266_ESP01
 esp01.build.core=esp8266
 esp01.build.variant=esp01
 
+esp01.menu.CpuFrequency.80=80MHz
+esp01.menu.CpuFrequency.80.build.f_cpu=80000000L
+
+esp01.menu.CpuFrequency.160=160MHz
+esp01.menu.CpuFrequency.160.build.f_cpu=160000000L
+
 esp01.upload.tool=esptool
 esp01.menu.UploadSpeed.115200=115200
 esp01.menu.UploadSpeed.115200.upload.speed=115200

hardware/esp8266com/esp8266/cores/esp8266/core_esp8266_main.cpp

@@ -37,12 +37,24 @@ extern "C" {
 
 int atexit(void (*func)()) { return 0; }
 
+extern "C" void ets_update_cpu_frequency(int freqmhz); 
 void initVariant() __attribute__((weak));
 void initVariant() { }
 
 extern void loop();
 extern void setup();
 
+void preloop_update_frequency() __attribute__((weak));
+void preloop_update_frequency()
+{
+#if defined(F_CPU) && (F_CPU == 16000000L)
+    REG_SET_BIT(0x3ff00014, BIT(0));
+    ets_update_cpu_frequency(160);
+#endif
+}
+
+
+
 extern void (*__init_array_start)(void);
 extern void (*__init_array_end)(void);
 
@@ -87,6 +99,7 @@ static void loop_wrapper()
         setup();
         setup_done = true;
     }
+    preloop_update_frequency();
     loop();
     esp_schedule();
 }