nrf/modules/machine/soft_pwm: Add PWM for nrf51x boards using soft PWM.

Using extmod/machine_pwm.c for the Python bindings and the existing
softpwm.c driver, by just adding the interface.

Properties:
- Frequency range 1-3906 Hz.
- All PWM outputs run at the same frequency but can have different duty
  cycles.
- Limited to the P0.x pins.

Since it uses the existing softpwm.c mechanism, it will be affected by
playing music with the music class.

ports/nrf/boards/microbit/mpconfigboard.h

@@ -30,6 +30,7 @@
 
 #define MICROPY_PY_MACHINE_UART     (1)
 #define MICROPY_PY_MUSIC            (1)
+#define MICROPY_PY_MACHINE_PWM      (1)
 #define MICROPY_PY_MACHINE_SOFT_PWM (1)
 #define MICROPY_PY_MACHINE_HW_SPI   (1)
 #define MICROPY_PY_MACHINE_RTCOUNTER (1)

ports/nrf/boards/pca10000/mpconfigboard.h

@@ -35,6 +35,9 @@
 #define MICROPY_PY_MACHINE_ADC      (0)
 #define MICROPY_PY_MACHINE_TEMP     (1)
 
+#define MICROPY_PY_MACHINE_PWM      (1)
+#define MICROPY_PY_MACHINE_SOFT_PWM (1)
+
 #define MICROPY_HW_ENABLE_RNG       (1)
 
 #define MICROPY_HW_HAS_LED          (1)

ports/nrf/boards/pca10001/mpconfigboard.h

@@ -35,6 +35,9 @@
 #define MICROPY_PY_MACHINE_ADC      (1)
 #define MICROPY_PY_MACHINE_TEMP     (1)
 
+#define MICROPY_PY_MACHINE_PWM      (1)
+#define MICROPY_PY_MACHINE_SOFT_PWM (1)
+
 #define MICROPY_HW_ENABLE_RNG       (1)
 
 #define MICROPY_HW_HAS_LED          (1)

ports/nrf/boards/pca10028/mpconfigboard.h

@@ -35,6 +35,9 @@
 #define MICROPY_PY_MACHINE_ADC      (1)
 #define MICROPY_PY_MACHINE_TEMP     (1)
 
+#define MICROPY_PY_MACHINE_PWM      (1)
+#define MICROPY_PY_MACHINE_SOFT_PWM (1)
+
 #define MICROPY_HW_ENABLE_RNG       (1)
 
 #define MICROPY_HW_HAS_LED          (1)

ports/nrf/boards/pca10031/mpconfigboard.h

@@ -35,6 +35,9 @@
 #define MICROPY_PY_MACHINE_ADC      (1)
 #define MICROPY_PY_MACHINE_TEMP     (1)
 
+#define MICROPY_PY_MACHINE_PWM      (1)
+#define MICROPY_PY_MACHINE_SOFT_PWM (1)
+
 #define MICROPY_HW_ENABLE_RNG       (1)
 
 #define MICROPY_HW_HAS_LED          (1)

ports/nrf/modules/machine/modmachine.c

@@ -42,7 +42,7 @@
 #include "spi.h"
 #include "i2c.h"
 #include "timer.h"
-#if MICROPY_PY_MACHINE_HW_PWM
+#if MICROPY_PY_MACHINE_HW_PWM || MICROPY_PY_MACHINE_SOFT_PWM
 #include "pwm.h"
 #endif
 #if MICROPY_PY_MACHINE_ADC
@@ -235,7 +235,7 @@ STATIC const mp_rom_map_elem_t machine_module_globals_table[] = {
 #if MICROPY_PY_MACHINE_TIMER_NRF
     { MP_ROM_QSTR(MP_QSTR_Timer),              MP_ROM_PTR(&machine_timer_type) },
 #endif
-#if MICROPY_PY_MACHINE_HW_PWM
+#if MICROPY_PY_MACHINE_HW_PWM || MICROPY_PY_MACHINE_SOFT_PWM
     { MP_ROM_QSTR(MP_QSTR_PWM),                MP_ROM_PTR(&machine_pwm_type) },
 #endif
 #if MICROPY_PY_MACHINE_TEMP

ports/nrf/modules/machine/soft_pwm.c

@@ -0,0 +1,214 @@
+/*
+ * This file is part of the MicroPython project, http://micropython.org/
+ *
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2023 Robert Hammelrath
+ *
+ * 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 "py/runtime.h"
+#include "py/mphal.h"
+
+#if MICROPY_PY_MACHINE_SOFT_PWM
+
+#include "softpwm.h"
+
+typedef enum {
+    DUTY_NOT_SET = 0,
+    DUTY,
+    DUTY_U16,
+    DUTY_NS
+} pwm_duty_t;
+
+typedef struct _machine_pwm_obj_t {
+    mp_obj_base_t base;
+    uint8_t pwm_pin;
+    bool defer_start;
+    uint8_t duty_mode;
+    uint32_t duty;
+    uint32_t freq;
+} machine_pwm_obj_t;
+
+#define SOFT_PWM_BASE_FREQ      (1000000)
+#define DUTY_FULL_SCALE         (1024)
+
+STATIC void mp_machine_pwm_print(const mp_print_t *print, mp_obj_t self_in, mp_print_kind_t kind) {
+    machine_pwm_obj_t *self = self_in;
+    static char *duty_suffix[] = { "", "", "_u16", "_ns" };
+    mp_printf(print, "<PWM: Pin=%u freq=%dHz duty%s=%d>",
+        self->pwm_pin, self->freq,
+        duty_suffix[self->duty_mode], self->duty);
+}
+
+// MicroPython bindings for machine API
+
+STATIC void machine_soft_pwm_start(machine_pwm_obj_t *self);
+STATIC void mp_machine_pwm_deinit(machine_pwm_obj_t *self);
+STATIC void mp_machine_pwm_freq_set(machine_pwm_obj_t *self, mp_int_t freq);
+STATIC void mp_machine_pwm_duty_set(machine_pwm_obj_t *self, mp_int_t duty);
+STATIC void mp_machine_pwm_duty_set_u16(machine_pwm_obj_t *self, mp_int_t duty_u16);
+STATIC void mp_machine_pwm_duty_set_ns(machine_pwm_obj_t *self, mp_int_t duty_ns);
+
+STATIC void mp_machine_pwm_init_helper(machine_pwm_obj_t *self, size_t n_args, const mp_obj_t *pos_args, mp_map_t *kw_args) {
+    enum { ARG_freq, ARG_duty, ARG_duty_u16, ARG_duty_ns };
+    static const mp_arg_t allowed_args[] = {
+        { MP_QSTR_freq,     MP_ARG_KW_ONLY | MP_ARG_INT, {.u_int = -1} },
+        { MP_QSTR_duty,     MP_ARG_KW_ONLY | MP_ARG_INT, {.u_int = -1} },
+        { MP_QSTR_duty_u16, MP_ARG_KW_ONLY | MP_ARG_INT, {.u_int = -1} },
+        { MP_QSTR_duty_ns,  MP_ARG_KW_ONLY | 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);
+
+    self->defer_start = true;
+    if (args[ARG_freq].u_int != -1) {
+        mp_machine_pwm_freq_set(self, args[ARG_freq].u_int);
+    }
+    if (args[ARG_duty].u_int != -1) {
+        mp_machine_pwm_duty_set(self, args[ARG_duty].u_int);
+    }
+    if (args[ARG_duty_u16].u_int != -1) {
+        mp_machine_pwm_duty_set_u16(self, args[ARG_duty_u16].u_int);
+    }
+    if (args[ARG_duty_ns].u_int != -1) {
+        mp_machine_pwm_duty_set_ns(self, args[ARG_duty_ns].u_int);
+    }
+    self->defer_start = false;
+    // (Re-)start the PWM.
+    machine_soft_pwm_start(self);
+}
+
+STATIC mp_obj_t mp_machine_pwm_make_new(const mp_obj_type_t *type, size_t n_args, size_t n_kw, const mp_obj_t *args) {
+    enum { ARG_pin, ARG_freq, ARG_duty, ARG_duty_u16, ARG_duty_ns, ARG_id };
+
+    mp_arg_check_num(n_args, n_kw, 1, MP_OBJ_FUN_ARGS_MAX, true);
+
+    // check if the PWM pin is valid.
+    int pwm_pin = mp_hal_get_pin_obj(args[0])->pin;
+    if (pwm_pin > 31) {
+        mp_raise_ValueError(MP_ERROR_TEXT("Pin number >31"));
+    }
+
+    machine_pwm_obj_t *self = mp_obj_malloc(machine_pwm_obj_t, &machine_pwm_type);;
+    self->defer_start = false;
+    self->pwm_pin = pwm_pin;
+    self->duty_mode = DUTY_NOT_SET;
+    self->duty = 0;
+    self->freq = 0;
+
+    // parse the remaining arguments and start the PWM
+    mp_map_t kw_args;
+    mp_map_init_fixed_table(&kw_args, n_kw, args + n_args);
+    mp_machine_pwm_init_helper(self, n_args - 1, args + 1, &kw_args);
+
+    return MP_OBJ_FROM_PTR(self);
+}
+
+STATIC void mp_machine_pwm_deinit(machine_pwm_obj_t *self) {
+    pwm_release(self->pwm_pin);
+}
+
+STATIC mp_obj_t mp_machine_pwm_freq_get(machine_pwm_obj_t *self) {
+    return MP_OBJ_NEW_SMALL_INT(self->freq);
+}
+
+STATIC void mp_machine_pwm_freq_set(machine_pwm_obj_t *self, mp_int_t freq) {
+
+    if (freq > (SOFT_PWM_BASE_FREQ / 256)) {
+        mp_raise_ValueError(MP_ERROR_TEXT("frequency out of range"));
+    }
+    self->freq = freq;
+    machine_soft_pwm_start(self);
+}
+
+STATIC mp_obj_t mp_machine_pwm_duty_get(machine_pwm_obj_t *self) {
+    if (self->duty_mode) {
+        return MP_OBJ_NEW_SMALL_INT(self->duty);
+    } else if (self->duty_mode == DUTY_U16) {
+        return MP_OBJ_NEW_SMALL_INT(self->duty * 100 / 65536);
+    } else {
+        return MP_OBJ_NEW_SMALL_INT(-1);
+    }
+}
+
+STATIC void mp_machine_pwm_duty_set(machine_pwm_obj_t *self, mp_int_t duty) {
+    self->duty = duty;
+    self->duty_mode = DUTY;
+    machine_soft_pwm_start(self);
+}
+
+STATIC mp_obj_t mp_machine_pwm_duty_get_u16(machine_pwm_obj_t *self) {
+    if (self->duty_mode == DUTY_U16) {
+        return MP_OBJ_NEW_SMALL_INT(self->duty);
+    } else if (self->duty_mode == DUTY) {
+        return MP_OBJ_NEW_SMALL_INT(self->duty * 65536 / 100);
+    } else {
+        return MP_OBJ_NEW_SMALL_INT(-1);
+    }
+}
+
+STATIC void mp_machine_pwm_duty_set_u16(machine_pwm_obj_t *self, mp_int_t duty) {
+    self->duty = duty;
+    self->duty_mode = DUTY_U16;
+    machine_soft_pwm_start(self);
+}
+
+STATIC mp_obj_t mp_machine_pwm_duty_get_ns(machine_pwm_obj_t *self) {
+    if (self->duty_mode == DUTY_NS) {
+        return MP_OBJ_NEW_SMALL_INT(self->duty);
+    } else {
+        return MP_OBJ_NEW_SMALL_INT(-1);
+    }
+}
+
+STATIC void mp_machine_pwm_duty_set_ns(machine_pwm_obj_t *self, mp_int_t duty) {
+    self->duty = duty;
+    self->duty_mode = DUTY_NS;
+    machine_soft_pwm_start(self);
+}
+
+/* Interface for the implementation */
+
+STATIC void machine_soft_pwm_start(machine_pwm_obj_t *self) {
+
+    // check if ready to go
+    if (self->defer_start == true || self->freq == 0 || self->duty_mode == DUTY_NOT_SET) {
+        return; // Not ready yet.
+    }
+
+    int ret = pwm_set_period_us(SOFT_PWM_BASE_FREQ / self->freq);
+
+    if (ret >= 0) {
+        int duty_width;
+        if (self->duty_mode == DUTY) {
+            duty_width = self->duty * DUTY_FULL_SCALE / 100;
+        } else if (self->duty_mode == DUTY_U16) {
+            duty_width = self->duty * DUTY_FULL_SCALE / 65536;
+        }if (self->duty_mode == DUTY_NS) {
+            duty_width = (uint64_t)self->duty * self->freq * DUTY_FULL_SCALE / 1000000000ULL;
+        }
+        pwm_set_duty_cycle(self->pwm_pin, duty_width);
+    }
+}
+
+#endif // MICROPY_PY_MACHINE_HW_PWM

ports/nrf/mpconfigport.h

@@ -202,6 +202,8 @@
 
 #if MICROPY_PY_MACHINE_HW_PWM
 #define MICROPY_PY_MACHINE_PWM_INCLUDEFILE "ports/nrf/modules/machine/pwm.c"
+#elif MICROPY_PY_MACHINE_SOFT_PWM
+#define MICROPY_PY_MACHINE_PWM_INCLUDEFILE "ports/nrf/modules/machine/soft_pwm.c"
 #endif
 
 #ifndef MICROPY_PY_MACHINE_TIMER_NRF