stmhal/servo.c - lite/micropython - Linaro Git Browser

 /*
  * This file is part of the Micro Python project, http://micropython.org/
  *
  * The MIT License (MIT)
  *
  * Copyright (c) 2013, 2014 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 "stm32f4xx_hal.h"

 #include "mpconfig.h"
 #include "nlr.h"
 #include "misc.h"
 #include "qstr.h"
 #include "obj.h"
 #include "runtime.h"
 #include "timer.h"
 #include "servo.h"

 /// \moduleref pyb
 /// \class Servo - 3-wire hobby servo driver
 ///
 /// Servo controls standard hobby servos with 3-wires (ground, power, signal).

 // this servo driver uses hardware PWM to drive servos on PA0, PA1, PA2, PA3 = X1, X2, X3, X4
 // TIM2 and TIM5 have CH1, CH2, CH3, CH4 on PA0-PA3 respectively
 // they are both 32-bit counters with 16-bit prescaler
 // we use TIM5

 #define PYB_SERVO_NUM (4)

 typedef struct _pyb_servo_obj_t {
     mp_obj_base_t base;
     uint8_t servo_id;
     uint8_t pulse_min;          // units of 10us
     uint8_t pulse_max;          // units of 10us
     uint8_t pulse_centre;       // units of 10us
     uint8_t pulse_angle_90;     // units of 10us; pulse at 90 degrees, minus pulse_centre
     uint8_t pulse_speed_100;    // units of 10us; pulse at 100% forward speed, minus pulse_centre
     uint16_t pulse_cur;         // units of 10us
     uint16_t pulse_dest;        // units of 10us
     int16_t pulse_accum;
     uint16_t time_left;
 } pyb_servo_obj_t;

 STATIC pyb_servo_obj_t pyb_servo_obj[PYB_SERVO_NUM];

 void servo_init(void) {
     timer_tim5_init();

     // reset servo objects
     for (int i = 0; i < PYB_SERVO_NUM; i++) {
         pyb_servo_obj[i].base.type = &pyb_servo_type;
         pyb_servo_obj[i].servo_id = i + 1;
         pyb_servo_obj[i].pulse_min = 64;
         pyb_servo_obj[i].pulse_max = 242;
         pyb_servo_obj[i].pulse_centre = 150;
         pyb_servo_obj[i].pulse_angle_90 = 97;
         pyb_servo_obj[i].pulse_speed_100 = 70;
         pyb_servo_obj[i].pulse_cur = 150;
         pyb_servo_obj[i].pulse_dest = 0;
         pyb_servo_obj[i].time_left = 0;
     }
 }

 void servo_timer_irq_callback(void) {
     bool need_it = false;
     for (int i = 0; i < PYB_SERVO_NUM; i++) {
         pyb_servo_obj_t *s = &pyb_servo_obj[i];
         if (s->pulse_cur != s->pulse_dest) {
             // clamp pulse to within min/max
             if (s->pulse_dest < s->pulse_min) {
                 s->pulse_dest = s->pulse_min;
             } else if (s->pulse_dest > s->pulse_max) {
                 s->pulse_dest = s->pulse_max;
             }
             // adjust cur to get closer to dest
             if (s->time_left <= 1) {
                 s->pulse_cur = s->pulse_dest;
                 s->time_left = 0;
             } else {
                 s->pulse_accum += s->pulse_dest - s->pulse_cur;
                 s->pulse_cur += s->pulse_accum / s->time_left;
                 s->pulse_accum %= s->time_left;
                 s->time_left--;
                 need_it = true;
             }
             // set the pulse width
             switch (s->servo_id) {
                 case 1: TIM5->CCR1 = s->pulse_cur; break;
                 case 2: TIM5->CCR2 = s->pulse_cur; break;
                 case 3: TIM5->CCR3 = s->pulse_cur; break;
                 case 4: TIM5->CCR4 = s->pulse_cur; break;
             }
         }
     }
     if (need_it) {
         __HAL_TIM_ENABLE_IT(&TIM5_Handle, TIM_IT_UPDATE);
     } else {
         __HAL_TIM_DISABLE_IT(&TIM5_Handle, TIM_IT_UPDATE);
     }
 }

 STATIC void servo_init_channel(pyb_servo_obj_t *s) {
     uint32_t pin;
     uint32_t channel;
     switch (s->servo_id) {
         case 1: pin = GPIO_PIN_0; channel = TIM_CHANNEL_1; break;
         case 2: pin = GPIO_PIN_1; channel = TIM_CHANNEL_2; break;
         case 3: pin = GPIO_PIN_2; channel = TIM_CHANNEL_3; break;
         case 4: pin = GPIO_PIN_3; channel = TIM_CHANNEL_4; break;
         default: return;
     }

     // GPIO configuration
     GPIO_InitTypeDef GPIO_InitStructure;
     GPIO_InitStructure.Pin = pin;
     GPIO_InitStructure.Mode = GPIO_MODE_AF_PP;
     GPIO_InitStructure.Speed = GPIO_SPEED_FAST;
     GPIO_InitStructure.Pull = GPIO_NOPULL;
     GPIO_InitStructure.Alternate = GPIO_AF2_TIM5;
     HAL_GPIO_Init(GPIOA, &GPIO_InitStructure);

     // PWM mode configuration
     TIM_OC_InitTypeDef oc_init;
     oc_init.OCMode = TIM_OCMODE_PWM1;
     oc_init.Pulse = s->pulse_cur; // units of 10us
     oc_init.OCPolarity = TIM_OCPOLARITY_HIGH;
     oc_init.OCFastMode = TIM_OCFAST_DISABLE;
     HAL_TIM_PWM_ConfigChannel(&TIM5_Handle, &oc_init, channel);

     // start PWM
     HAL_TIM_PWM_Start(&TIM5_Handle, channel);
 }

 /******************************************************************************/
 // Micro Python bindings

 STATIC mp_obj_t pyb_servo_set(mp_obj_t port, mp_obj_t value) {
     int p = mp_obj_get_int(port);
     int v = mp_obj_get_int(value);
     if (v < 50) { v = 50; }
     if (v > 250) { v = 250; }
     switch (p) {
         case 1: TIM5->CCR1 = v; break;
         case 2: TIM5->CCR2 = v; break;
         case 3: TIM5->CCR3 = v; break;
         case 4: TIM5->CCR4 = v; break;
     }
     return mp_const_none;
 }

 MP_DEFINE_CONST_FUN_OBJ_2(pyb_servo_set_obj, pyb_servo_set);

 STATIC mp_obj_t pyb_pwm_set(mp_obj_t period, mp_obj_t pulse) {
     int pe = mp_obj_get_int(period);
     int pu = mp_obj_get_int(pulse);
     TIM5->ARR = pe;
     TIM5->CCR3 = pu;
     return mp_const_none;
 }

 MP_DEFINE_CONST_FUN_OBJ_2(pyb_pwm_set_obj, pyb_pwm_set);

 STATIC void pyb_servo_print(void (*print)(void *env, const char *fmt, ...), void *env, mp_obj_t self_in, mp_print_kind_t kind) {
     pyb_servo_obj_t *self = self_in;
     print(env, "<Servo %lu at %luus>", self->servo_id, 10 * self->pulse_cur);
 }

 /// \classmethod \constructor(id)
 /// Create a servo object.  `id` is 1-4.
 STATIC mp_obj_t pyb_servo_make_new(mp_obj_t type_in, uint n_args, uint n_kw, const mp_obj_t *args) {
     // check arguments
     mp_arg_check_num(n_args, n_kw, 1, 1, false);

     // get servo number
     mp_int_t servo_id = mp_obj_get_int(args[0]) - 1;

     // check servo number
     if (!(0 <= servo_id && servo_id < PYB_SERVO_NUM)) {
         nlr_raise(mp_obj_new_exception_msg_varg(&mp_type_ValueError, "Servo %d does not exist", servo_id + 1));
     }

     // get and init servo object
     pyb_servo_obj_t *s = &pyb_servo_obj[servo_id];
     s->pulse_dest = s->pulse_cur;
     s->time_left = 0;
     servo_init_channel(s);

     return s;
 }

 /// \method pulse_width([value])
 /// Get or set the pulse width in milliseconds.
 STATIC mp_obj_t pyb_servo_pulse_width(uint n_args, const mp_obj_t *args) {
     pyb_servo_obj_t *self = args[0];
     if (n_args == 1) {
         // get pulse width, in us
         return mp_obj_new_int(10 * self->pulse_cur);
     } else {
         // set pulse width, in us
         self->pulse_dest = mp_obj_get_int(args[1]) / 10;
         self->time_left = 0;
         servo_timer_irq_callback();
         return mp_const_none;
     }
 }
 STATIC MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(pyb_servo_pulse_width_obj, 1, 2, pyb_servo_pulse_width);

 /// \method calibration([pulse_min, pulse_max, pulse_centre, [pulse_angle_90, pulse_speed_100]])
 /// Get or set the calibration of the servo timing.
 // TODO should accept 1 arg, a 5-tuple of values to set
 STATIC mp_obj_t pyb_servo_calibration(uint n_args, const mp_obj_t *args) {
     pyb_servo_obj_t *self = args[0];
     if (n_args == 1) {
         // get calibration values
         mp_obj_t tuple[5];
         tuple[0] = mp_obj_new_int(10 * self->pulse_min);
         tuple[1] = mp_obj_new_int(10 * self->pulse_max);
         tuple[2] = mp_obj_new_int(10 * self->pulse_centre);
         tuple[3] = mp_obj_new_int(10 * (self->pulse_angle_90 + self->pulse_centre));
         tuple[4] = mp_obj_new_int(10 * (self->pulse_speed_100 + self->pulse_centre));
         return mp_obj_new_tuple(5, tuple);
     } else if (n_args >= 4) {
         // set min, max, centre
         self->pulse_min = mp_obj_get_int(args[1]) / 10;
         self->pulse_max = mp_obj_get_int(args[2]) / 10;
         self->pulse_centre = mp_obj_get_int(args[3]) / 10;
         if (n_args == 4) {
             return mp_const_none;
         } else if (n_args == 6) {
             self->pulse_angle_90 = mp_obj_get_int(args[4]) / 10 - self->pulse_centre;
             self->pulse_speed_100 = mp_obj_get_int(args[5]) / 10 - self->pulse_centre;
             return mp_const_none;
         }
     }

     // bad number of arguments
     nlr_raise(mp_obj_new_exception_msg_varg(&mp_type_TypeError, "calibration expecting 1, 4 or 6 arguments, got %d", n_args));
 }
 STATIC MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(pyb_servo_calibration_obj, 1, 6, pyb_servo_calibration);

 /// \method angle([angle, time=0])
 /// Get or set the angle of the servo.
 ///
 ///   - `angle` is the angle to move to in degrees.
 ///   - `time` is the number of milliseconds to take to get to the specified angle.
 STATIC mp_obj_t pyb_servo_angle(uint n_args, const mp_obj_t *args) {
     pyb_servo_obj_t *self = args[0];
     if (n_args == 1) {
         // get angle
         return mp_obj_new_int((self->pulse_cur - self->pulse_centre) * 90 / self->pulse_angle_90);
     } else {
 #if MICROPY_PY_BUILTINS_FLOAT
         self->pulse_dest = self->pulse_centre + self->pulse_angle_90 * mp_obj_get_float(args[1]) / 90.0;
 #else
         self->pulse_dest = self->pulse_centre + self->pulse_angle_90 * mp_obj_get_int(args[1]) / 90;
 #endif
         if (n_args == 2) {
             // set angle immediately
             self->time_left = 0;
         } else {
             // set angle over a given time (given in milli seconds)
             self->time_left = mp_obj_get_int(args[2]) / 20;
             self->pulse_accum = 0;
         }
         servo_timer_irq_callback();
         return mp_const_none;
     }
 }
 STATIC MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(pyb_servo_angle_obj, 1, 3, pyb_servo_angle);

 /// \method speed([speed, time=0])
 /// Get or set the speed of a continuous rotation servo.
 ///
 ///   - `speed` is the speed to move to change to, between -100 and 100.
 ///   - `time` is the number of milliseconds to take to get to the specified speed.
 STATIC mp_obj_t pyb_servo_speed(uint n_args, const mp_obj_t *args) {
     pyb_servo_obj_t *self = args[0];
     if (n_args == 1) {
         // get speed
         return mp_obj_new_int((self->pulse_cur - self->pulse_centre) * 100 / self->pulse_speed_100);
     } else {
 #if MICROPY_PY_BUILTINS_FLOAT
         self->pulse_dest = self->pulse_centre + self->pulse_speed_100 * mp_obj_get_float(args[1]) / 100.0;
 #else
         self->pulse_dest = self->pulse_centre + self->pulse_speed_100 * mp_obj_get_int(args[1]) / 100;
 #endif
         if (n_args == 2) {
             // set speed immediately
             self->time_left = 0;
         } else {
             // set speed over a given time (given in milli seconds)
             self->time_left = mp_obj_get_int(args[2]) / 20;
             self->pulse_accum = 0;
         }
         servo_timer_irq_callback();
         return mp_const_none;
     }
 }

 STATIC MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(pyb_servo_speed_obj, 1, 3, pyb_servo_speed);

 STATIC const mp_map_elem_t pyb_servo_locals_dict_table[] = {
     { MP_OBJ_NEW_QSTR(MP_QSTR_pulse_width), (mp_obj_t)&pyb_servo_pulse_width_obj },
     { MP_OBJ_NEW_QSTR(MP_QSTR_calibration), (mp_obj_t)&pyb_servo_calibration_obj },
     { MP_OBJ_NEW_QSTR(MP_QSTR_angle), (mp_obj_t)&pyb_servo_angle_obj },
     { MP_OBJ_NEW_QSTR(MP_QSTR_speed), (mp_obj_t)&pyb_servo_speed_obj },
 };

 STATIC MP_DEFINE_CONST_DICT(pyb_servo_locals_dict, pyb_servo_locals_dict_table);

 const mp_obj_type_t pyb_servo_type = {
     { &mp_type_type },
     .name = MP_QSTR_Servo,
     .print = pyb_servo_print,
     .make_new = pyb_servo_make_new,
     .locals_dict = (mp_obj_t)&pyb_servo_locals_dict,
 };
	/*
	* This file is part of the Micro Python project, http://micropython.org/
	*
	* The MIT License (MIT)
	*
	* Copyright (c) 2013, 2014 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 "stm32f4xx_hal.h"

	#include "mpconfig.h"
	#include "nlr.h"
	#include "misc.h"
	#include "qstr.h"
	#include "obj.h"
	#include "runtime.h"
	#include "timer.h"
	#include "servo.h"

	/// \moduleref pyb
	/// \class Servo - 3-wire hobby servo driver
	///
	/// Servo controls standard hobby servos with 3-wires (ground, power, signal).

	// this servo driver uses hardware PWM to drive servos on PA0, PA1, PA2, PA3 = X1, X2, X3, X4
	// TIM2 and TIM5 have CH1, CH2, CH3, CH4 on PA0-PA3 respectively
	// they are both 32-bit counters with 16-bit prescaler
	// we use TIM5

	#define PYB_SERVO_NUM (4)

	typedef struct _pyb_servo_obj_t {
	mp_obj_base_t base;
	uint8_t servo_id;
	uint8_t pulse_min; // units of 10us
	uint8_t pulse_max; // units of 10us
	uint8_t pulse_centre; // units of 10us
	uint8_t pulse_angle_90; // units of 10us; pulse at 90 degrees, minus pulse_centre
	uint8_t pulse_speed_100; // units of 10us; pulse at 100% forward speed, minus pulse_centre
	uint16_t pulse_cur; // units of 10us
	uint16_t pulse_dest; // units of 10us
	int16_t pulse_accum;
	uint16_t time_left;
	} pyb_servo_obj_t;

	STATIC pyb_servo_obj_t pyb_servo_obj[PYB_SERVO_NUM];

	void servo_init(void) {
	timer_tim5_init();

	// reset servo objects
	for (int i = 0; i < PYB_SERVO_NUM; i++) {
	pyb_servo_obj[i].base.type = &pyb_servo_type;
	pyb_servo_obj[i].servo_id = i + 1;
	pyb_servo_obj[i].pulse_min = 64;
	pyb_servo_obj[i].pulse_max = 242;
	pyb_servo_obj[i].pulse_centre = 150;
	pyb_servo_obj[i].pulse_angle_90 = 97;
	pyb_servo_obj[i].pulse_speed_100 = 70;
	pyb_servo_obj[i].pulse_cur = 150;
	pyb_servo_obj[i].pulse_dest = 0;
	pyb_servo_obj[i].time_left = 0;
	}
	}

	void servo_timer_irq_callback(void) {
	bool need_it = false;
	for (int i = 0; i < PYB_SERVO_NUM; i++) {
	pyb_servo_obj_t *s = &pyb_servo_obj[i];
	if (s->pulse_cur != s->pulse_dest) {
	// clamp pulse to within min/max
	if (s->pulse_dest < s->pulse_min) {
	s->pulse_dest = s->pulse_min;
	} else if (s->pulse_dest > s->pulse_max) {
	s->pulse_dest = s->pulse_max;
	}
	// adjust cur to get closer to dest
	if (s->time_left <= 1) {
	s->pulse_cur = s->pulse_dest;
	s->time_left = 0;
	} else {
	s->pulse_accum += s->pulse_dest - s->pulse_cur;
	s->pulse_cur += s->pulse_accum / s->time_left;
	s->pulse_accum %= s->time_left;
	s->time_left--;
	need_it = true;
	}
	// set the pulse width
	switch (s->servo_id) {
	case 1: TIM5->CCR1 = s->pulse_cur; break;
	case 2: TIM5->CCR2 = s->pulse_cur; break;
	case 3: TIM5->CCR3 = s->pulse_cur; break;
	case 4: TIM5->CCR4 = s->pulse_cur; break;
	}
	}
	}
	if (need_it) {
	__HAL_TIM_ENABLE_IT(&TIM5_Handle, TIM_IT_UPDATE);
	} else {
	__HAL_TIM_DISABLE_IT(&TIM5_Handle, TIM_IT_UPDATE);
	}
	}

	STATIC void servo_init_channel(pyb_servo_obj_t *s) {
	uint32_t pin;
	uint32_t channel;
	switch (s->servo_id) {
	case 1: pin = GPIO_PIN_0; channel = TIM_CHANNEL_1; break;
	case 2: pin = GPIO_PIN_1; channel = TIM_CHANNEL_2; break;
	case 3: pin = GPIO_PIN_2; channel = TIM_CHANNEL_3; break;
	case 4: pin = GPIO_PIN_3; channel = TIM_CHANNEL_4; break;
	default: return;
	}

	// GPIO configuration
	GPIO_InitTypeDef GPIO_InitStructure;
	GPIO_InitStructure.Pin = pin;
	GPIO_InitStructure.Mode = GPIO_MODE_AF_PP;
	GPIO_InitStructure.Speed = GPIO_SPEED_FAST;
	GPIO_InitStructure.Pull = GPIO_NOPULL;
	GPIO_InitStructure.Alternate = GPIO_AF2_TIM5;
	HAL_GPIO_Init(GPIOA, &GPIO_InitStructure);

	// PWM mode configuration
	TIM_OC_InitTypeDef oc_init;
	oc_init.OCMode = TIM_OCMODE_PWM1;
	oc_init.Pulse = s->pulse_cur; // units of 10us
	oc_init.OCPolarity = TIM_OCPOLARITY_HIGH;
	oc_init.OCFastMode = TIM_OCFAST_DISABLE;
	HAL_TIM_PWM_ConfigChannel(&TIM5_Handle, &oc_init, channel);

	// start PWM
	HAL_TIM_PWM_Start(&TIM5_Handle, channel);
	}

	/******************************************************************************/
	// Micro Python bindings

	STATIC mp_obj_t pyb_servo_set(mp_obj_t port, mp_obj_t value) {
	int p = mp_obj_get_int(port);
	int v = mp_obj_get_int(value);
	if (v < 50) { v = 50; }
	if (v > 250) { v = 250; }
	switch (p) {
	case 1: TIM5->CCR1 = v; break;
	case 2: TIM5->CCR2 = v; break;
	case 3: TIM5->CCR3 = v; break;
	case 4: TIM5->CCR4 = v; break;
	}
	return mp_const_none;
	}

	MP_DEFINE_CONST_FUN_OBJ_2(pyb_servo_set_obj, pyb_servo_set);

	STATIC mp_obj_t pyb_pwm_set(mp_obj_t period, mp_obj_t pulse) {
	int pe = mp_obj_get_int(period);
	int pu = mp_obj_get_int(pulse);
	TIM5->ARR = pe;
	TIM5->CCR3 = pu;
	return mp_const_none;
	}

	MP_DEFINE_CONST_FUN_OBJ_2(pyb_pwm_set_obj, pyb_pwm_set);

	STATIC void pyb_servo_print(void (print)(void env, const char fmt, ...), void env, mp_obj_t self_in, mp_print_kind_t kind) {
	pyb_servo_obj_t *self = self_in;
	print(env, "<Servo %lu at %luus>", self->servo_id, 10 * self->pulse_cur);
	}

	/// \classmethod \constructor(id)
	/// Create a servo object. `id` is 1-4.
	STATIC mp_obj_t pyb_servo_make_new(mp_obj_t type_in, uint n_args, uint n_kw, const mp_obj_t *args) {
	// check arguments
	mp_arg_check_num(n_args, n_kw, 1, 1, false);

	// get servo number
	mp_int_t servo_id = mp_obj_get_int(args[0]) - 1;

	// check servo number
	if (!(0 <= servo_id && servo_id < PYB_SERVO_NUM)) {
	nlr_raise(mp_obj_new_exception_msg_varg(&mp_type_ValueError, "Servo %d does not exist", servo_id + 1));
	}

	// get and init servo object
	pyb_servo_obj_t *s = &pyb_servo_obj[servo_id];
	s->pulse_dest = s->pulse_cur;
	s->time_left = 0;
	servo_init_channel(s);

	return s;
	}

	/// \method pulse_width([value])
	/// Get or set the pulse width in milliseconds.
	STATIC mp_obj_t pyb_servo_pulse_width(uint n_args, const mp_obj_t *args) {
	pyb_servo_obj_t *self = args[0];
	if (n_args == 1) {
	// get pulse width, in us
	return mp_obj_new_int(10 * self->pulse_cur);
	} else {
	// set pulse width, in us
	self->pulse_dest = mp_obj_get_int(args[1]) / 10;
	self->time_left = 0;
	servo_timer_irq_callback();
	return mp_const_none;
	}
	}
	STATIC MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(pyb_servo_pulse_width_obj, 1, 2, pyb_servo_pulse_width);

	/// \method calibration([pulse_min, pulse_max, pulse_centre, [pulse_angle_90, pulse_speed_100]])
	/// Get or set the calibration of the servo timing.
	// TODO should accept 1 arg, a 5-tuple of values to set
	STATIC mp_obj_t pyb_servo_calibration(uint n_args, const mp_obj_t *args) {
	pyb_servo_obj_t *self = args[0];
	if (n_args == 1) {
	// get calibration values
	mp_obj_t tuple[5];
	tuple[0] = mp_obj_new_int(10 * self->pulse_min);
	tuple[1] = mp_obj_new_int(10 * self->pulse_max);
	tuple[2] = mp_obj_new_int(10 * self->pulse_centre);
	tuple[3] = mp_obj_new_int(10 * (self->pulse_angle_90 + self->pulse_centre));
	tuple[4] = mp_obj_new_int(10 * (self->pulse_speed_100 + self->pulse_centre));
	return mp_obj_new_tuple(5, tuple);
	} else if (n_args >= 4) {
	// set min, max, centre
	self->pulse_min = mp_obj_get_int(args[1]) / 10;
	self->pulse_max = mp_obj_get_int(args[2]) / 10;
	self->pulse_centre = mp_obj_get_int(args[3]) / 10;
	if (n_args == 4) {
	return mp_const_none;
	} else if (n_args == 6) {
	self->pulse_angle_90 = mp_obj_get_int(args[4]) / 10 - self->pulse_centre;
	self->pulse_speed_100 = mp_obj_get_int(args[5]) / 10 - self->pulse_centre;
	return mp_const_none;
	}
	}

	// bad number of arguments
	nlr_raise(mp_obj_new_exception_msg_varg(&mp_type_TypeError, "calibration expecting 1, 4 or 6 arguments, got %d", n_args));
	}
	STATIC MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(pyb_servo_calibration_obj, 1, 6, pyb_servo_calibration);

	/// \method angle([angle, time=0])
	/// Get or set the angle of the servo.
	///
	/// - `angle` is the angle to move to in degrees.
	/// - `time` is the number of milliseconds to take to get to the specified angle.
	STATIC mp_obj_t pyb_servo_angle(uint n_args, const mp_obj_t *args) {
	pyb_servo_obj_t *self = args[0];
	if (n_args == 1) {
	// get angle
	return mp_obj_new_int((self->pulse_cur - self->pulse_centre) * 90 / self->pulse_angle_90);
	} else {
	#if MICROPY_PY_BUILTINS_FLOAT
	self->pulse_dest = self->pulse_centre + self->pulse_angle_90 * mp_obj_get_float(args[1]) / 90.0;
	#else
	self->pulse_dest = self->pulse_centre + self->pulse_angle_90 * mp_obj_get_int(args[1]) / 90;
	#endif
	if (n_args == 2) {
	// set angle immediately
	self->time_left = 0;
	} else {
	// set angle over a given time (given in milli seconds)
	self->time_left = mp_obj_get_int(args[2]) / 20;
	self->pulse_accum = 0;
	}
	servo_timer_irq_callback();
	return mp_const_none;
	}
	}
	STATIC MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(pyb_servo_angle_obj, 1, 3, pyb_servo_angle);

	/// \method speed([speed, time=0])
	/// Get or set the speed of a continuous rotation servo.
	///
	/// - `speed` is the speed to move to change to, between -100 and 100.
	/// - `time` is the number of milliseconds to take to get to the specified speed.
	STATIC mp_obj_t pyb_servo_speed(uint n_args, const mp_obj_t *args) {
	pyb_servo_obj_t *self = args[0];
	if (n_args == 1) {
	// get speed
	return mp_obj_new_int((self->pulse_cur - self->pulse_centre) * 100 / self->pulse_speed_100);
	} else {
	#if MICROPY_PY_BUILTINS_FLOAT
	self->pulse_dest = self->pulse_centre + self->pulse_speed_100 * mp_obj_get_float(args[1]) / 100.0;
	#else
	self->pulse_dest = self->pulse_centre + self->pulse_speed_100 * mp_obj_get_int(args[1]) / 100;
	#endif
	if (n_args == 2) {
	// set speed immediately
	self->time_left = 0;
	} else {
	// set speed over a given time (given in milli seconds)
	self->time_left = mp_obj_get_int(args[2]) / 20;
	self->pulse_accum = 0;
	}
	servo_timer_irq_callback();
	return mp_const_none;
	}
	}

	STATIC MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(pyb_servo_speed_obj, 1, 3, pyb_servo_speed);

	STATIC const mp_map_elem_t pyb_servo_locals_dict_table[] = {
	{ MP_OBJ_NEW_QSTR(MP_QSTR_pulse_width), (mp_obj_t)&pyb_servo_pulse_width_obj },
	{ MP_OBJ_NEW_QSTR(MP_QSTR_calibration), (mp_obj_t)&pyb_servo_calibration_obj },
	{ MP_OBJ_NEW_QSTR(MP_QSTR_angle), (mp_obj_t)&pyb_servo_angle_obj },
	{ MP_OBJ_NEW_QSTR(MP_QSTR_speed), (mp_obj_t)&pyb_servo_speed_obj },
	};

	STATIC MP_DEFINE_CONST_DICT(pyb_servo_locals_dict, pyb_servo_locals_dict_table);

	const mp_obj_type_t pyb_servo_type = {
	{ &mp_type_type },
	.name = MP_QSTR_Servo,
	.print = pyb_servo_print,
	.make_new = pyb_servo_make_new,
	.locals_dict = (mp_obj_t)&pyb_servo_locals_dict,
	};