Can a generator in the ESP32 MCPWM be triggered by different comparators?

Question

I want to control stepper motors with an ESP32 directly via a L298 power driver. That works with fullstep mode, but I cannot generate the signals for halfstep mode (Enable, In1, In2 In3, In4). Here is the constructor of the control class:

    McpwmStepperControl::McpwmStepperControl(gpio_num_t In1, gpio_num_t In2,
        gpio_num_t EnA, gpio_num_t In3, gpio_num_t In4, gpio_num_t EnB, gpio_num_t CapPin, gpio_num_t RefPin, int GroupID)
            : _reverse(false), _In1(In1), _In2(In2), _EnA(EnA), _In3(In3), _In4(In4), _EnB(EnB), _CapPin(CapPin), _RefPin(RefPin),
             _GroupID(GroupID), _direction(false), _error_relay(0), _debounce(0),
             Timer(GroupID),
             Operator{McpwmOperator(GroupID), McpwmOperator(GroupID), McpwmOperator(GroupID)},
             Comparator{McpwmComparator(Operator[0]), McpwmComparator(Operator[1]), McpwmComparator(Operator[2])},
             Generator{McpwmGenerator(Operator[0], In1, 0), McpwmGenerator(Operator[0], In2, 1),
                 McpwmGenerator(Operator[1], In3, 0), McpwmGenerator(Operator[1], In4, 1),
                 McpwmGenerator(Operator[2], EnA, 0), McpwmGenerator(Operator[2], EnB, 0) } 
{
    setSpeeds(10, 150); // set default values
    _dp = GPIO_NUM_NC;
    Operator[0].connectTimer(Timer);
    Operator[1].connectTimer(Timer);
    Operator[2].connectTimer(Timer);
    Timer.setComparators(&Comparator);
}

Here is how I try to initialize one of the generators:

    ESP_ERROR_CHECK(mcpwm_generator_set_actions_on_timer_event(Generator[0].getHandle(),
            MCPWM_GEN_COMPARE_EVENT_ACTION(MCPWM_TIMER_DIRECTION_UP, Comparator[0].getHandle(), MCPWM_GEN_ACTION_TOGGLE),
            MCPWM_GEN_COMPARE_EVENT_ACTION(MCPWM_TIMER_DIRECTION_UP, Comparator[1].getHandle(), MCPWM_GEN_ACTION_TOGGLE),
            MCPWM_GEN_COMPARE_EVENT_ACTION(MCPWM_TIMER_DIRECTION_UP, Comparator[2].getHandle(), MCPWM_GEN_ACTION_TOGGLE),
            MCPWM_GEN_COMPARE_EVENT_ACTION(MCPWM_TIMER_DIRECTION_DOWN, Comparator[2].getHandle(), MCPWM_GEN_ACTION_TOGGLE),
            MCPWM_GEN_COMPARE_EVENT_ACTION(MCPWM_TIMER_DIRECTION_DOWN, Comparator[1].getHandle(), MCPWM_GEN_ACTION_TOGGLE),
            MCPWM_GEN_COMPARE_EVENT_ACTION(MCPWM_TIMER_DIRECTION_DOWN, Comparator[0].getHandle(), MCPWM_GEN_ACTION_TOGGLE),
            MCPWM_GEN_COMPARE_EVENT_ACTION_END()
            ));

The code compiles and starts ok, but no it only toggles at the Comparator[0] events. (I commented out all combinations of MCPWM_GEN_COMPARE_EVENT_ACTION macros, but I always get the same waveform). Is this a trivial coding bug or a limitation of the ESP32 MCPWM hardware?

The yellow channel is triggered by timer full and empty and the blue channel is the generator output. As you can see, it only toggles on Comparator[0].

Here is the link to the complete code on github:

https://github.com/tommiport5/McpwmTest.git

tommiport5 · Accepted Answer · 2024-10-24 07:52:48Z

0

I actually found limitations in the implementation of th MCPWM hardware, which were not so clear to me from the documentation:

A group can have 3 operators.
One operator can have up to 2 comparators.
One operator can have up to 2 generators.
A generator can only react on comparator events from its own operator.

With these limitations I currently don't see a way to generate the 4 independent signals for half step mode. Feel free to use my test system on github as a base for your research.

edited Oct 24, 2024 at 7:52

answered Oct 22, 2024 at 14:32

tommiport5

919 bronze badges

Sign up to request clarification or add additional context in comments.

Collectives™ on Stack Overflow

Can a generator in the ESP32 MCPWM be triggered by different comparators?

1 Answer 1

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Related