Initial HW PWM (Delta-Sigma)

extras/hw_pwm/component.mk

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+# Component makefile for private/hw_pwm
+
+INC_DIRS += $(ROOT)private/hw_pwm
+
+# args for passing into compile rule generation
+private/hw_pwm_INC_DIR =  $(ROOT)private/hw_pwm
+private/hw_pwm_SRC_DIR =  $(ROOT)private/hw_pwm
+
+$(eval $(call component_compile_rules,private/hw_pwm))

extras/hw_pwm/pwm.c

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+/* Implementation of HW PWM support.
+ *
+ * Part of esp-open-rtos
+ * Copyright (C) 2018 ourairquality (https://github.com/ourairquality)
+ * Copyright (C) 2018 Zaltora (https://github.com/Zaltora)
+ * BSD Licensed as described in the file LICENSE
+ */
+#include "pwm.h"
+
+#include <espressif/esp_common.h>
+#include <esp8266.h>
+
+
+#ifdef PWM_DEBUG
+#define debug(fmt, ...) printf("%s: " fmt "\n", "HW_PWM", ## __VA_ARGS__)
+#else
+#define debug(fmt, ...)
+#endif
+
+typedef struct pwmInfoDefinition
+{
+    uint8_t running;
+    uint8_t preScale;
+    uint8_t dutyCycle;
+    bool output;
+
+    /* private */
+    uint8_t usedPins;
+    uint8_t pins[8];
+} PWMInfo;
+
+static PWMInfo pwmInfo;
+
+void hw_pwm_init(uint8_t npins, const uint8_t* pins)
+{
+    /* Assert number of pins is correct */
+    if (npins > MAX_PWM_PINS)
+    {
+        debug("Incorrect number of PWM pins (%d)\n", npins);
+        return;
+    }
+
+    /* Save pins information */
+    pwmInfo.usedPins = npins;
+
+    for (uint8_t i = 0 ; i < npins; ++i)
+    {
+        pwmInfo.pins[i] = pins[i];
+        /* configure GPIOs */
+        gpio_enable(pins[i], GPIO_OUTPUT);
+    }
+
+    /* Set output to LOW */
+    hw_pwm_stop();
+
+    /* Flag not running */
+    pwmInfo.running = 0;
+}
+
+//FIXME: Need Confirmation
+// Freq = (80,000,000/prescale) * (target / 256) HZ           (0   < target < 128)
+// Freq = (80,000,000/prescale) * ((256 - target) / 256)  HZ  (128 < target < 256)
+void hw_pwm_set_prescale(uint8_t prescale)
+{
+    //TODO: Add a freq/prescale converter
+    pwmInfo.preScale = prescale;
+    debug("Set Prescale: %u",pwmInfo.preScale);
+}
+
+void hw_pwm_set_duty(uint8_t duty)
+{
+    pwmInfo.dutyCycle = duty;
+    if (duty == 0 || duty == UINT8_MAX)
+    {
+      pwmInfo.output = (duty == UINT8_MAX);
+    }
+    debug("Duty set at %u",pwmInfo.dutyCycle);
+    hw_pwm_restart();
+}
+
+void hw_pwm_restart()
+{
+    if (pwmInfo.running)
+    {
+        hw_pwm_stop();
+        hw_pwm_start();
+    }
+}
+
+void hw_pwm_start()
+{
+    if (pwmInfo.dutyCycle > 0 && pwmInfo.dutyCycle < UINT8_MAX)
+    {
+        for (uint8_t i = 0; i < pwmInfo.usedPins; ++i)
+        {
+            SET_MASK_BITS(GPIO.CONF[pwmInfo.pins[i]], GPIO_CONF_SOURCE_PWM);
+        }
+        GPIO.PWM = GPIO_PWM_ENABLE | (pwmInfo.preScale << 8) | pwmInfo.dutyCycle;
+    }
+    else
+    {
+      for (uint8_t i = 0; i < pwmInfo.usedPins; ++i)
+      {
+        gpio_write(pwmInfo.pins[i], pwmInfo.output );
+      }       
+    }
+    debug("start");
+    pwmInfo.running = 1;
+}
+
+void hw_pwm_stop()
+{
+    for (uint8_t i = 0; i < pwmInfo.usedPins; ++i)
+    {
+      CLEAR_MASK_BITS(GPIO.CONF[pwmInfo.pins[i]], GPIO_CONF_SOURCE_PWM);
+      gpio_write(pwmInfo.pins[i], false);
+    }       
+    debug("stop");
+    pwmInfo.running = 0;
+}

extras/hw_pwm/pwm.h

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+/* Implementation of HW PWM support.
+ *
+ * Part of esp-open-rtos
+ * Copyright (C) 2018 ourairquality (https://github.com/ourairquality)
+ * Copyright (C) 2018 Zaltora (https://github.com/Zaltora)
+ * BSD Licensed as described in the file LICENSE
+ */
+#ifndef EXTRAS_HW_PWM_H_
+#define EXTRAS_HW_PWM_H_
+
+#include <stdint.h>
+
+#define MAX_PWM_PINS    8
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+void hw_pwm_init(uint8_t npins, const uint8_t* pins);
+void hw_pwm_set_prescale(uint8_t prescale);
+void hw_pwm_set_duty(uint8_t duty);
+
+void hw_pwm_restart();
+void hw_pwm_start();
+void hw_pwm_stop();
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* EXTRAS_HW_PWM_H_ */