add ledc and sigma-delta api

cores/esp32/esp32-hal-ledc.h

@@ -0,0 +1,36 @@
+// Copyright 2015-2016 Espressif Systems (Shanghai) PTE LTD
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef _ESP32_HAL_LEDC_H_
+#define _ESP32_HAL_LEDC_H_
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#include <stdint.h>
+#include <stdbool.h>
+
+//channel 0-15 resolution 1-16bits freq limits depend on resolution
+uint32_t    ledcSetup(uint8_t channel, uint32_t freq, uint8_t resolution_bits);
+void        ledcWrite(uint8_t channel, uint32_t duty);
+uint32_t    ledcRead(uint8_t channel);
+void        ledcAttachPin(uint8_t pin, uint8_t channel);
+void        ledcDetachPin(uint8_t pin);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* _ESP32_HAL_LEDC_H_ */