esp32: Add PWM support via machine.PWM class.

This patch adds the machine.PWM class.

Code lineage:

I started by copying the esp8266 machine_pwm.c. I used information from the
ESP32 Technical Reference Manual, the esp-idf documentation, and the SDK's
sample ledc example code (but I did not copy that code, just studied it to
understand the SDK's API for PWM). So aside from the code copied from the
esp8266 PWM support, everything else you see is just new code I wrote.

I wasn't an employee of anybody when I wrote it, and I wrote it with the
understanding and intention that it's simply a derivative work of the
existing micropython code. I freely and willingly contribute it to the
project and intend that it not change the legal status of the micropython
code base in any way, even if it is included in that base in whole or part.

Author: Andy Valencia

esp32/Makefile

@@ -123,6 +123,7 @@ SRC_C = \
 	machine_touchpad.c \
 	machine_adc.c \
 	machine_dac.c \
+	machine_pwm.c \
 	modmachine.c \
 	modnetwork.c \
 	modsocket.c \

esp32/machine_pwm.c

@@ -0,0 +1,277 @@
+/*
+ * This file is part of the Micro Python project, http://micropython.org/
+ *
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2016 Damien P. George
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+#include <stdio.h>
+#include "driver/ledc.h"
+#include "esp_err.h"
+
+#include "py/nlr.h"
+#include "py/runtime.h"
+#include "modmachine.h"
+#include "mphalport.h"
+
+// Forward dec'l
+extern const mp_obj_type_t machine_pwm_type;
+
+typedef struct _esp32_pwm_obj_t {
+    mp_obj_base_t base;
+    gpio_num_t pin;
+    uint8_t active;
+    uint8_t channel;
+} esp32_pwm_obj_t;
+
+// Which channel has which GPIO pin assigned?
+// (-1 if not assigned)
+STATIC int chan_gpio[LEDC_CHANNEL_MAX];
+
+// Params for PW operation
+// 5khz
+#define PWFREQ (5000)
+// High speed mode
+#define PWMODE (LEDC_HIGH_SPEED_MODE)
+// 10-bit resolution (compatible with esp8266 PWM)
+#define PWRES (LEDC_TIMER_10_BIT)
+// Timer 1
+#define PWTIMER (LEDC_TIMER_1)
+
+// Config of timer upon which we run all PWM'ed GPIO pins
+STATIC bool pwm_inited = false;
+STATIC ledc_timer_config_t timer_cfg = {
+    .bit_num = PWRES,
+    .freq_hz = PWFREQ,
+    .speed_mode = PWMODE,
+    .timer_num = PWTIMER
+};
+
+STATIC void pwm_init(void) {
+
+    // Initial condition: no channels assigned
+    for (int x = 0; x < LEDC_CHANNEL_MAX; ++x) {
+        chan_gpio[x] = -1;
+    }
+
+    // Init with default timer params
+    ledc_timer_config(&timer_cfg);
+}
+
+STATIC int set_freq(int newval) {
+    int oval = timer_cfg.freq_hz;
+
+    timer_cfg.freq_hz = newval;
+    if (ledc_timer_config(&timer_cfg) != ESP_OK) {
+        timer_cfg.freq_hz = oval;
+        return 0;
+    }
+    return 1;
+}
+
+/******************************************************************************/
+
+// MicroPython bindings for PWM
+
+STATIC void esp32_pwm_print(const mp_print_t *print, mp_obj_t self_in, mp_print_kind_t kind) {
+    esp32_pwm_obj_t *self = MP_OBJ_TO_PTR(self_in);
+    mp_printf(print, "PWM(%u", self->pin);
+    if (self->active) {
+        mp_printf(print, ", freq=%u, duty=%u", timer_cfg.freq_hz,
+            ledc_get_duty(PWMODE, self->channel));
+    }
+    mp_printf(print, ")");
+}
+
+STATIC void esp32_pwm_init_helper(esp32_pwm_obj_t *self,
+        size_t n_args, const mp_obj_t *pos_args, mp_map_t *kw_args) {
+    enum { ARG_freq, ARG_duty };
+    static const mp_arg_t allowed_args[] = {
+        { MP_QSTR_freq, MP_ARG_INT, {.u_int = -1} },
+        { MP_QSTR_duty, MP_ARG_INT, {.u_int = -1} },
+    };
+    mp_arg_val_t args[MP_ARRAY_SIZE(allowed_args)];
+    mp_arg_parse_all(n_args, pos_args, kw_args,
+        MP_ARRAY_SIZE(allowed_args), allowed_args, args);
+
+    int channel;
+    int avail = -1;
+
+    // Find a free PWM channel, also spot if our pin is
+    //  already mentioned.
+    for (channel = 0; channel < LEDC_CHANNEL_MAX; ++channel) {
+        if (chan_gpio[channel] == self->pin) {
+            break;
+        }
+        if ((avail == -1) && (chan_gpio[channel] == -1)) {
+            avail = channel;
+        }
+    }
+    if (channel >= LEDC_CHANNEL_MAX) {
+        if (avail == -1) {
+            mp_raise_ValueError("out of PWM channels");
+        }
+        channel = avail;
+    }
+
+    // New PWM assignment
+    self->active = 1;
+    if (chan_gpio[channel] == -1) {
+        ledc_channel_config_t cfg = {
+            .channel = channel,
+            .duty = (1 << PWRES) / 2,
+            .gpio_num = self->pin,
+            .intr_type = LEDC_INTR_DISABLE,
+            .speed_mode = PWMODE,
+            .timer_sel = PWTIMER,
+        };
+        if (ledc_channel_config(&cfg) != ESP_OK) {
+            nlr_raise(mp_obj_new_exception_msg_varg(&mp_type_ValueError,
+                "PWM not supported on pin %d", self->pin));
+        }
+        chan_gpio[channel] = self->pin;
+        self->channel = channel;
+    }
+
+    // Maybe change PWM timer
+    int tval = args[ARG_freq].u_int;
+    if (tval != -1) {
+        if (tval != timer_cfg.freq_hz) {
+            if (!set_freq(tval)) {
+                nlr_raise(mp_obj_new_exception_msg_varg(&mp_type_ValueError,
+                    "Bad frequency %d", tval));
+            }
+        }
+    }
+
+    // Set duty cycle?
+    int dval = args[ARG_duty].u_int;
+    if (dval != -1) {
+        dval &= ((1 << PWRES)-1);
+        ledc_set_duty(PWMODE, channel, dval);
+        ledc_update_duty(PWMODE, channel);
+    }
+}
+
+STATIC mp_obj_t esp32_pwm_make_new(const mp_obj_type_t *type,
+        size_t n_args, size_t n_kw, const mp_obj_t *args) {
+    mp_arg_check_num(n_args, n_kw, 1, MP_OBJ_FUN_ARGS_MAX, true);
+    gpio_num_t pin_id = machine_pin_get_id(args[0]);
+
+    // create PWM object from the given pin
+    esp32_pwm_obj_t *self = m_new_obj(esp32_pwm_obj_t);
+    self->base.type = &machine_pwm_type;
+    self->pin = pin_id;
+    self->active = 0;
+    self->channel = -1;
+
+    // start the PWM subsystem if it's not already running
+    if (!pwm_inited) {
+        pwm_init();
+        pwm_inited = true;
+    }
+
+    // start the PWM running for this channel
+    mp_map_t kw_args;
+    mp_map_init_fixed_table(&kw_args, n_kw, args + n_args);
+    esp32_pwm_init_helper(self, n_args - 1, args + 1, &kw_args);
+
+    return MP_OBJ_FROM_PTR(self);
+}
+
+STATIC mp_obj_t esp32_pwm_init(size_t n_args,
+        const mp_obj_t *args, mp_map_t *kw_args) {
+    esp32_pwm_init_helper(args[0], n_args - 1, args + 1, kw_args);
+    return mp_const_none;
+}
+MP_DEFINE_CONST_FUN_OBJ_KW(esp32_pwm_init_obj, 1, esp32_pwm_init);
+
+STATIC mp_obj_t esp32_pwm_deinit(mp_obj_t self_in) {
+    esp32_pwm_obj_t *self = MP_OBJ_TO_PTR(self_in);
+    int chan = self->channel;
+
+    // Valid channel?
+    if ((chan >= 0) && (chan < LEDC_CHANNEL_MAX)) {
+        // Mark it unused, and tell the hardware to stop routing
+        chan_gpio[chan] = -1;
+        ledc_stop(PWMODE, chan, 0);
+        self->active = 0;
+        self->channel = -1;
+    }
+    return mp_const_none;
+}
+STATIC MP_DEFINE_CONST_FUN_OBJ_1(esp32_pwm_deinit_obj, esp32_pwm_deinit);
+
+STATIC mp_obj_t esp32_pwm_freq(size_t n_args, const mp_obj_t *args) {
+    if (n_args == 1) {
+        // get
+        return MP_OBJ_NEW_SMALL_INT(timer_cfg.freq_hz);
+    }
+
+    // set
+    int tval = mp_obj_get_int(args[1]);
+    if (!set_freq(tval)) {
+        nlr_raise(mp_obj_new_exception_msg_varg(&mp_type_ValueError,
+            "Bad frequency %d", tval));
+    }
+    return mp_const_none;
+}
+
+STATIC MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(esp32_pwm_freq_obj, 1, 2, esp32_pwm_freq);
+
+STATIC mp_obj_t esp32_pwm_duty(size_t n_args, const mp_obj_t *args) {
+    esp32_pwm_obj_t *self = MP_OBJ_TO_PTR(args[0]);
+    int duty;
+
+    if (n_args == 1) {
+        // get
+        duty = ledc_get_duty(PWMODE, self->channel);
+        return MP_OBJ_NEW_SMALL_INT(duty);
+    }
+
+    // set
+    duty = mp_obj_get_int(args[1]);
+    duty &= ((1 << PWRES)-1);
+    ledc_set_duty(PWMODE, self->channel, duty);
+    ledc_update_duty(PWMODE, self->channel);
+
+    return mp_const_none;
+}
+STATIC MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(esp32_pwm_duty_obj,
+    1, 2, esp32_pwm_duty);
+
+STATIC const mp_rom_map_elem_t esp32_pwm_locals_dict_table[] = {
+    { MP_ROM_QSTR(MP_QSTR_init), MP_ROM_PTR(&esp32_pwm_init_obj) },
+    { MP_ROM_QSTR(MP_QSTR_deinit), MP_ROM_PTR(&esp32_pwm_deinit_obj) },
+    { MP_ROM_QSTR(MP_QSTR_freq), MP_ROM_PTR(&esp32_pwm_freq_obj) },
+    { MP_ROM_QSTR(MP_QSTR_duty), MP_ROM_PTR(&esp32_pwm_duty_obj) },
+};
+
+STATIC MP_DEFINE_CONST_DICT(esp32_pwm_locals_dict,
+    esp32_pwm_locals_dict_table);
+
+const mp_obj_type_t machine_pwm_type = {
+    { &mp_type_type },
+    .name = MP_QSTR_PWM,
+    .print = esp32_pwm_print,
+    .make_new = esp32_pwm_make_new,
+    .locals_dict = (mp_obj_dict_t*)&esp32_pwm_locals_dict,
+};

esp32/modmachine.c

@@ -118,6 +118,7 @@ STATIC const mp_rom_map_elem_t machine_module_globals_table[] = {
     { MP_ROM_QSTR(MP_QSTR_ADC), MP_ROM_PTR(&machine_adc_type) },
     { MP_ROM_QSTR(MP_QSTR_DAC), MP_ROM_PTR(&machine_dac_type) },
     { MP_ROM_QSTR(MP_QSTR_I2C), MP_ROM_PTR(&machine_i2c_type) },
+    { MP_ROM_QSTR(MP_QSTR_PWM), MP_ROM_PTR(&machine_pwm_type) },
     { MP_ROM_QSTR(MP_QSTR_SPI), MP_ROM_PTR(&mp_machine_soft_spi_type) },
 };
 

esp32/modmachine.h

@@ -7,6 +7,7 @@ extern const mp_obj_type_t machine_pin_type;
 extern const mp_obj_type_t machine_touchpad_type;
 extern const mp_obj_type_t machine_adc_type;
 extern const mp_obj_type_t machine_dac_type;
+extern const mp_obj_type_t machine_pwm_type;
 extern const mp_obj_type_t machine_hw_spi_type;
 
 void machine_pins_init(void);