Add single-led support for SenseCAP Watcher (#373)

* add single-led support for SenseCAP Watcher

* Rename blaklight.cc to backlight.cc

main/boards/sensecap-watcher/config.h

@@ -28,7 +28,7 @@
 
 
 
-#define BUILTIN_LED_GPIO        GPIO_NUM_NC
+#define BUILTIN_LED_GPIO        GPIO_NUM_40
 #define BOOT_BUTTON_GPIO        GPIO_NUM_0
 #define VOLUME_UP_BUTTON_GPIO   GPIO_NUM_NC
 #define VOLUME_DOWN_BUTTON_GPIO GPIO_NUM_NC

main/boards/sensecap-watcher/sensecap_watcher.cc

@@ -7,6 +7,7 @@
 #include "application.h"
 #include "button.h"
 #include "config.h"
+#include "led/single_led.h"
 #include "iot/thing_manager.h"
 #include "power_save_timer.h"
 
@@ -280,6 +281,14 @@ public:
         return &backlight;
     }
 
+    // 根据 https://github.com/Seeed-Studio/OSHW-SenseCAP-Watcher/blob/main/Hardware/SenseCAP_Watcher_v1.0_SCH.pdf
+    // RGB LED型号为 ws2813 mini, 连接在GPIO 40，供电电压 3.3v, 没有连接 BIN 双信号线
+    // 可以直接兼容SingleLED采用的ws2812
+    virtual Led* GetLed() override {
+        static SingleLed led(BUILTIN_LED_GPIO);
+        return &led;
+    }
+
     virtual void SetPowerSaveMode(bool enabled) override {
         if (!enabled) {
             power_save_timer_->WakeUp();