[FL-2797] Signal Generator app (#1793)

* Signal Generator app
* MCO pin initialization in app
* furi_hal_pwm documentation

Co-authored-by: あく <alleteam@gmail.com>

firmware/targets/f7/furi_hal/furi_hal_pwm.h

@@ -0,0 +1,42 @@
+/**
+ * @file furi_hal_pwm.h
+ * PWM contol HAL
+ */
+#pragma once
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#include <stdint.h>
+
+typedef enum {
+    FuriHalPwmOutputIdTim1PA7,
+    FuriHalPwmOutputIdLptim2PA4,
+} FuriHalPwmOutputId;
+
+/** Enable PWM channel and set parameters
+ * 
+ * @param[in]  channel  PWM channel (FuriHalPwmOutputId)
+ * @param[in]  freq  Frequency in Hz
+ * @param[in]  duty  Duty cycle value in %
+*/
+void furi_hal_pwm_start(FuriHalPwmOutputId channel, uint32_t freq, uint8_t duty);
+
+/** Disable PWM channel
+ * 
+ * @param[in]  channel  PWM channel (FuriHalPwmOutputId)
+*/
+void furi_hal_pwm_stop(FuriHalPwmOutputId channel);
+
+/** Set PWM channel parameters
+ * 
+ * @param[in]  channel  PWM channel (FuriHalPwmOutputId)
+ * @param[in]  freq  Frequency in Hz
+ * @param[in]  duty  Duty cycle value in %
+*/
+void furi_hal_pwm_set_params(FuriHalPwmOutputId channel, uint32_t freq, uint8_t duty);
+
+#ifdef __cplusplus
+}
+#endif