• Three Phase Centre Aligned MC PWM

    Paul Gould02/13/2020 at 15:25 0 comments

    Starting point for Brushless motor control is the get the required features up and running. The ESP-32 has a MCPWM (Motor Control)  hardware block. The hardest part was getting the "centre aligned" working with the many different types of sync function. The one I needed was missing from the header file.

    mcpwm.h for the ESP32 is missing some enums

    /**
     * @brief MCPWM select sync signal input
     */
    typedef enum {
        MCPWM_SELECT_SYNC_OFF          /*!< SYNC is off*/
        MCPWM_SELECT_SYNC_INT0,        /*!<Select SYNC0 as internal*/
        MCPWM_SELECT_SYNC_INT1,        /*!<Select SYNC1 as internal*/
        MCPWM_SELECT_SYNC_INT2,        /*!<Select SYNC2 as internal*/
        MCPWM_SELECT_SYNC0,            /*!<Select SYNC0 as input*/
        MCPWM_SELECT_SYNC1,            /*!<Select SYNC1 as input*/
        MCPWM_SELECT_SYNC2,            /*!<Select SYNC2 as input*/
    } mcpwm_sync_signal_t;

     The online file is located at

    https://github.com/espressif/arduino-esp32/blob/04963009eedfbc1e0ea2e1378ae69e7cebda6fd6/tools/sdk/include/driver/driver/mcpwm.h

    I have issued a bug fix request.

    Arduino ino file

    #include "driver/mcpwm.h"
    #include "soc/mcpwm_reg.h"
    #include "soc/mcpwm_struct.h"
    
    // MCPWM Pins
    #define GPIO_PWM0A_OUT 15   //Set GPIO 15 as PWM0A
    #define GPIO_PWM0B_OUT 02   //Set GPIO 02 as PWM0B
    #define GPIO_PWM1A_OUT 00   //Set GPIO 00 as PWM1A
    #define GPIO_PWM1B_OUT 04   //Set GPIO 04 as PWM1B
    #define GPIO_PWM2A_OUT 16   //Set GPIO 16 as PWM2A
    #define GPIO_PWM2B_OUT 17   //Set GPIO 17 as PWM2B
    
    static void setup_mcpwm_pins()
    {
        Serial.println("initializing mcpwm control gpio...n");
        mcpwm_gpio_init(MCPWM_UNIT_0, MCPWM0A, GPIO_PWM0A_OUT);
        mcpwm_gpio_init(MCPWM_UNIT_0, MCPWM0B, GPIO_PWM0B_OUT);
        mcpwm_gpio_init(MCPWM_UNIT_0, MCPWM1A, GPIO_PWM1A_OUT);
        mcpwm_gpio_init(MCPWM_UNIT_0, MCPWM1B, GPIO_PWM1B_OUT);
        mcpwm_gpio_init(MCPWM_UNIT_0, MCPWM2A, GPIO_PWM2A_OUT);
        mcpwm_gpio_init(MCPWM_UNIT_0, MCPWM2B, GPIO_PWM2B_OUT);  
    } // setup_pins()
    
    static void setup_mcpwm()
    {
       setup_mcpwm_pins();
    
       mcpwm_config_t pwm_config;
       pwm_config.frequency = 40000;  //frequency = 20000Hz
       pwm_config.cmpr_a = 50.0;      //duty cycle of PWMxA = 50.0%
       pwm_config.cmpr_b = 50.0;      //duty cycle of PWMxB = 50.0%
       pwm_config.counter_mode = MCPWM_UP_DOWN_COUNTER; // Up-down counter (triangle wave)
       pwm_config.duty_mode = MCPWM_DUTY_MODE_0; // Active HIGH
       mcpwm_init(MCPWM_UNIT_0, MCPWM_TIMER_0, &pwm_config);    //Configure PWM0A & PWM0B with above settings
       mcpwm_init(MCPWM_UNIT_0, MCPWM_TIMER_1, &pwm_config);    //Configure PWM0A & PWM0B with above settings
       mcpwm_init(MCPWM_UNIT_0, MCPWM_TIMER_2, &pwm_config);    //Configure PWM0A & PWM0B with above settings
    
       mcpwm_sync_enable(MCPWM_UNIT_0, MCPWM_TIMER_0, MCPWM_SELECT_SYNC_OUT0, 0);
       mcpwm_sync_enable(MCPWM_UNIT_0, MCPWM_TIMER_1, MCPWM_SELECT_SYNC_OUT0, 0);
       mcpwm_sync_enable(MCPWM_UNIT_0, MCPWM_TIMER_2, MCPWM_SELECT_SYNC_OUT0, 0);
      
       MCPWM0.timer[0].sync.out_sel = 1;
       delayMicroseconds(100);
       MCPWM0.timer[0].sync.out_sel = 0;
    
       mcpwm_set_duty(MCPWM_UNIT_0, MCPWM_TIMER_0, MCPWM_OPR_A, 70);
       mcpwm_set_duty(MCPWM_UNIT_0, MCPWM_TIMER_0, MCPWM_OPR_B, 60);
       mcpwm_set_duty(MCPWM_UNIT_0, MCPWM_TIMER_1, MCPWM_OPR_A, 50);
       mcpwm_set_duty(MCPWM_UNIT_0, MCPWM_TIMER_1, MCPWM_OPR_B, 40);
       mcpwm_set_duty(MCPWM_UNIT_0, MCPWM_TIMER_2, MCPWM_OPR_A, 30);
       mcpwm_set_duty(MCPWM_UNIT_0, MCPWM_TIMER_2, MCPWM_OPR_B, 20);
    } // setup_mcpwm
    
    void setup()
    {
       Serial.begin(115200);
       Serial.println( "Start ");
       setup_mcpwm();
    } // setup()
    
    void loop()
    {
       Serial.println("D");
       delay(500);
    } // loop()

    I will have to look at dead-time next, so I only have to set three PWM values instead of six.

    I could also save some pins and use the DRV8305 internal dead time feature. 

  • Project Notes

    Paul Gould02/11/2020 at 17:11 0 comments