The MCPWM peripheral is a versatile PWM generator, which contains various submodules to make it a key element in power electronic applications like motor control, digital power and so on. Typically, the MCPWM peripheral can be used in the following scenarios:
-**MCPWM Timer**: The time base of the final PWM signal, it also determines the event timing of other submodules.
-**MCPWM Operator**: The key module that is responsible for generating the PWM waveforms. It consists of other submodules, like comparator, PWM generator, dead-time and carrier modulator.
-**MCPWM Comparator**: The compare module takes the time-base count value as input, and continuously compare to the threshold value that configured by user. When the time-base counter is equal to any of the threshold value, an compare event will be generated and the MCPWM generator can update its level accordingly.
-**MCPWM Generator**: One MCPWM generator can generate a pair of PWM waves, complementarily or independently, based on various events triggered from other submodules like MCPWM Timer, MCPWM Comparator.
-**MCPWM Fault**: The fault module is used to detect the fault condition from outside, mainly via GPIO matrix. Once the fault signal is active, MCPWM Operator will force all the generators into a predefined state, to protect the system from damage.
-**MCPWM Sync**: The sync module is used to synchronize the MCPWM timers, so that the final PWM signals generated by different MCPWM generators can have a fixed phase difference. The sync signal can be routed from GPIO matrix or from MCPWM Timer event.
-**Dead Time**: This submodule is used to insert extra delay to the existing PWM edges that generated in the previous steps.
-**Carrier Modulation**: The carrier submodule allows a high-frequency carrier signal to modulate the PWM waveforms generated by the generator and dead time submodules. This capability is mandatory if you need pulse transformer-based gate drivers to control the power switching elements.
-**Brake**: MCPWM operator can set how to brake the generators when particular fault is detected. We can shut down the PWM output immediately or regulate the PWM output cycle by cycle, depends on how critical the fault is.
-**MCPWM Capture**: This is a standalone submodule which can work even without the above MCPWM operators. The capture consists one dedicated timer and several independent channels. Each channel is connected to the GPIO, a pulse on the GPIO will trigger the capture timer to store the time-base count value and then notify the user by interrupt. Using this feature, we can measure a pulse width precisely. What's more, the capture timer can also be synchronized by the MCPWM Sync submodule.
-`Resource Allocation and Initialization <#resource-allocation-and-initialization>`__ - covers how to allocate various MCPWM objects, like timers, operators, comparators, generators and so on. These objects are the basis of the following IO setting and control functions.
-`Timer Operations and Events <#timer-operations-and-events>`__ - describes control functions and event callbacks that supported by the MCPWM timer.
-`Comparator Operations and Events <#comparator-operations-and-events>`__ - describes control functions and event callbacks that supported by the MCPWM comparator.
-`Generator Actions on Events <#generator-actions-on-events>`__ - describes how to set actions for MCPWM generators on particular events that generated by the MCPWM timer and comparators.
-`Classical PWM Waveforms and Generator Configurations <#classical-pwm-waveforms-and-generator-configurations>`__ - demonstrates some classical PWM waveforms that can be achieved by configuring generator actions.
-`Dead Time <#dead-time>`__ - describes how to set dead time for MCPWM generators.
-`Classical PWM Waveforms and Dead Time Configurations <#classical-pwm-waveforms-and-dead-time-configurations>`__ - demonstrates some classical PWM waveforms that can be achieved by configuring dead time.
-`Carrier Modulation <#carrier-modulation>`__ - describes how to set modulate a high frequency onto the final PWM waveforms.
-`Faults and Brake Actions <#faults-and-brake-actions>`__ - describes how to set brake actions for MCPWM operators on particular fault event.
-`Generator Force Actions <#generator-force-actions>`__ - describes how to control the generator output level asynchronously in a forceful way.
-`Synchronization <#synchronization>`__ - describes how to synchronize the MCPWM timers and get a fixed phase difference between the generated PWM signals.
-`Capture <#capture>`__ - describes how to use the MCPWM capture module to measure the pulse width of a signal.
-`Power Management <#power-management>`__ - describes how different source clock will affect power consumption.
-`IRAM Safe <#iram-safe>`__ - describes tips on how to make the RMT interrupt work better along with a disabled cache.
-`Thread Safety <#thread-safety>`__ - lists which APIs are guaranteed to be thread safe by the driver.
-`Kconfig Options <#kconfig-options>`__ - lists the supported Kconfig options that can bring different effects to the driver.
As displayed in the diagram above, the MCPWM peripheral consists of several submodules. Each submodule has its own resource allocation, which is described in the following sections.
You can allocate a MCPWM timer object by calling :cpp:func:`mcpwm_new_timer` function, with a configuration structure :cpp:type:`mcpwm_timer_config_t` as the parameter. The configuration structure is defined as:
-:cpp:member:`mcpwm_timer_config_t::group_id` specifies the MCPWM group ID. The ID should belong to [0, :c:macro:`SOC_MCPWM_GROUPS` - 1] range. Please note, timers located in different groups are totally independent.
-:cpp:member:`mcpwm_timer_config_t::clk_src` sets the clock source of the timer.
-:cpp:member:`mcpwm_timer_config_t::resolution_hz` set the expected resolution of the timer, the driver internally will set a proper divider based on the clock source and the resolution.
-:cpp:member:`mcpwm_timer_config_t::count_mode` sets the count mode of the timer.
-:cpp:member:`mcpwm_timer_config_t::period_ticks` sets the period of the timer, in ticks (the tick resolution is set in the :cpp:member:`mcpwm_timer_config_t::resolution_hz`).
-:cpp:member:`mcpwm_timer_config_t::update_period_on_empty` sets whether to update the period value when the timer counts to zero.
-:cpp:member:`mcpwm_timer_config_t::update_period_on_sync` sets whether to update the period value when the timer takes a sync signal.
The :cpp:func:`mcpwm_new_timer` will return a pointer to the allocated timer object if the allocation succeeds. Otherwise, it will return error code. Specifically, when there are no more free timers in the MCPWM group, this function will return :c:macro:`ESP_ERR_NOT_FOUND` error. [1]_
You can allocate a MCPWM operator object by calling :cpp:func:`mcpwm_new_operator` function, with a configuration structure :cpp:type:`mcpwm_operator_config_t` as the parameter. The configuration structure is defined as:
-:cpp:member:`mcpwm_operator_config_t::group_id` specifies the MCPWM group ID. The ID should belong to [0, :c:macro:`SOC_MCPWM_GROUPS` - 1] range. Please note, operators located in different groups are totally independent.
-:cpp:member:`mcpwm_operator_config_t::update_gen_action_on_tez` sets whether to update the generator action when the timer counts to zero. Here and below, the timer refers to the one that is connected to the operator by :cpp:func:`mcpwm_operator_connect_timer`.
-:cpp:member:`mcpwm_operator_config_t::update_gen_action_on_tep` sets whether to update the generator action when the timer counts to peak.
-:cpp:member:`mcpwm_operator_config_t::update_gen_action_on_sync` sets whether to update the generator action when the timer takes a sync signal.
-:cpp:member:`mcpwm_operator_config_t::update_dead_time_on_tez` sets whether to update the dead time when the timer counts to zero.
-:cpp:member:`mcpwm_operator_config_t::update_dead_time_on_tep` sets whether to update the dead time when the timer counts to peak.
-:cpp:member:`mcpwm_operator_config_t::update_dead_time_on_sync` sets whether to update the dead time when the timer takes a sync signal.
The :cpp:func:`mcpwm_new_operator` will return a pointer to the allocated operator object if the allocation succeeds. Otherwise, it will return error code. Specifically, when there are no more free operators in the MCPWM group, this function will return :c:macro:`ESP_ERR_NOT_FOUND` error. [1]_
You can allocate a MCPWM comparator object by calling :cpp:func:`mcpwm_new_comparator` function, with a MCPWM operator handle and configuration structure :cpp:type:`mcpwm_comparator_config_t` as the parameter. The operator handle is created by :cpp:func:`mcpwm_new_operator`. The configuration structure is defined as:
The :cpp:func:`mcpwm_new_comparator` will return a pointer to the allocated comparator object if the allocation succeeds. Otherwise, it will return error code. Specifically, when there are no more free comparators in the MCPWM operator, this function will return :c:macro:`ESP_ERR_NOT_FOUND` error. [1]_
You can allocate a MCPWM generator object by calling :cpp:func:`mcpwm_new_generator` function, with a MCPWM operator handle and configuration structure :cpp:type:`mcpwm_generator_config_t` as the parameter. The operator handle is created by :cpp:func:`mcpwm_new_operator`. The configuration structure is defined as:
-:cpp:member:`mcpwm_generator_config_t::gen_gpio_num` sets the GPIO number used by the generator.
-:cpp:member:`mcpwm_generator_config_t::invert_pwm` sets whether to invert the PWM signal.
-:cpp:member:`mcpwm_generator_config_t::io_loop_back` sets whether to enable the loop back mode. It is for debugging purposes only. It enables both the GPIO's input and output ability through the GPIO matrix peripheral.
The :cpp:func:`mcpwm_new_generator` will return a pointer to the allocated generator object if the allocation succeeds. Otherwise, it will return error code. Specifically, when there are no more free generators in the MCPWM operator, this function will return :c:macro:`ESP_ERR_NOT_FOUND` error. [1]_
There are two types of faults: A fault signal reflected from the GPIO and a fault generated by software. To allocate a GPIO fault object, you can call :cpp:func:`mcpwm_new_gpio_fault` function, with configuration structure :cpp:type:`mcpwm_gpio_fault_config_t` as the parameter. The configuration structure is defined as:
-:cpp:member:`mcpwm_gpio_fault_config_t::group_id` sets the MCPWM group ID. The ID should belong to [0, :c:macro:`SOC_MCPWM_GROUPS` - 1] range. Please note, GPIO fault located in different groups are totally independent, i.e. GPIO fault in group 0 can not be detected by the operator in group 1.
-:cpp:member:`mcpwm_gpio_fault_config_t::gpio_num` sets the GPIO number used by the fault.
-:cpp:member:`mcpwm_gpio_fault_config_t::active_level` sets the active level of the fault signal.
-:cpp:member:`mcpwm_gpio_fault_config_t::pull_up` and :cpp:member:`mcpwm_gpio_fault_config_t::pull_down` set whether to pull up and/or pull down the GPIO internally.
-:cpp:member:`mcpwm_gpio_fault_config_t::io_loop_back` sets whether to enable the loop back mode. It is for debugging purposes only. It enables both the GPIO's input and output ability through the GPIO matrix peripheral.
The :cpp:func:`mcpwm_new_gpio_fault` will return a pointer to the allocated fault object if the allocation succeeds. Otherwise, it will return error code. Specifically, when there are no more free GPIO faults in the MCPWM group, this function will return :c:macro:`ESP_ERR_NOT_FOUND` error. [1]_
Software fault object can be used to trigger a fault by calling a function :cpp:func:`mcpwm_soft_fault_activate` instead of waiting for a real fault signal on the GPIO. A software fault object can be allocated by calling :cpp:func:`mcpwm_new_soft_fault` function, with configuration structure :cpp:type:`mcpwm_soft_fault_config_t` as the parameter. Currently this configuration structure is left for future purpose. :cpp:func:`mcpwm_new_soft_fault` function will return a pointer to the allocated fault object if the allocation succeeds. Otherwise, it will return error code. Specifically, when there are no memory left for the fault object, this function will return :c:macro:`ESP_ERR_NO_MEM` error. Although the software fault and GPIO fault are of different types, but the returned fault handle is of the same type.
On the contrary, calling :cpp:func:`mcpwm_del_fault` function will free the allocated fault object, this function works for both software and GPIO fault.
MCPWM Sync Sources
~~~~~~~~~~~~~~~~~~
The sync source is what can be used to synchronize the MCPWM timer and MCPWM capture timer. There're three types of sync sources: A sync source reflected from the GPIO, a sync source generated by software and a sync source generated by MCPWM timer event.
To allocate a GPIO sync source, you can call :cpp:func:`mcpwm_new_gpio_sync_src` function, with configuration structure :cpp:type:`mcpwm_gpio_sync_src_config_t` as the parameter. The configuration structure is defined as:
-:cpp:member:`mcpwm_gpio_sync_src_config_t::group_id` sets the MCPWM group ID. The ID should belong to [0, :c:macro:`SOC_MCPWM_GROUPS` - 1] range. Please note, GPIO sync source located in different groups are totally independent, i.e. GPIO sync source in group 0 can not be detected by the timers in group 1.
-:cpp:member:`mcpwm_gpio_sync_src_config_t::gpio_num` sets the GPIO number used by the sync source.
-:cpp:member:`mcpwm_gpio_sync_src_config_t::active_neg` sets whether the sync signal is active on falling edge.
-:cpp:member:`mcpwm_gpio_sync_src_config_t::pull_up` and :cpp:member:`mcpwm_gpio_sync_src_config_t::pull_down` set whether to pull up and/or pull down the GPIO internally.
-:cpp:member:`mcpwm_gpio_sync_src_config_t::io_loop_back` sets whether to enable the loop back mode. It is for debugging purposes only. It enables both the GPIO's input and output ability through the GPIO matrix peripheral.
The :cpp:func:`mcpwm_new_gpio_sync_src` will return a pointer to the allocated sync source object if the allocation succeeds. Otherwise, it will return error code. Specifically, when there are no more free GPIO sync sources in the MCPWM group, this function will return :c:macro:`ESP_ERR_NOT_FOUND` error. [1]_
To allocate a Timer event sync source, you can call :cpp:func:`mcpwm_new_timer_sync_src` function, with configuration structure :cpp:type:`mcpwm_timer_sync_src_config_t` as the parameter. The configuration structure is defined as:
-:cpp:member:`mcpwm_timer_sync_src_config_t::timer_event` specifies on what timer event to generate the sync signal.
-:cpp:member:`mcpwm_timer_sync_src_config_t::propagate_input_sync` sets whether to propagate the input sync signal (i.e. the input sync signal will be routed to its sync output).
The :cpp:func:`mcpwm_new_timer_sync_src` will return a pointer to the allocated sync source object if the allocation succeeds. Otherwise, it will return error code. Specifically, if a sync source has been allocated from the same timer before, this function will return :c:macro:`ESP_ERR_INVALID_STATE` error.
Last but not least, to allocate a software sync source, you can call :cpp:func:`mcpwm_new_soft_sync_src` function, with configuration structure :cpp:type:`mcpwm_soft_sync_config_t` as the parameter. Currently this configuration structure is left for future purpose. :cpp:func:`mcpwm_new_soft_sync_src` will return a pointer to the allocated sync source object if the allocation succeeds. Otherwise, it will return error code. Specifically, when there are no memory left for the sync source object, this function will return :c:macro:`ESP_ERR_NO_MEM` error. Please note, to make a software sync source take effect, don't forget to call :cpp:func:`mcpwm_soft_sync_activate`.
On the contrary, calling :cpp:func:`mcpwm_del_sync_src` function will free the allocated sync source object, this function works for all types of sync sources.
MCPWM Capture Timer and Channels
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The MCPWM group has a dedicated timer which is used to capture the timestamp when specific event occurred. The capture timer is connected with several independent channels, each channel is assigned with a GPIO.
To allocate a capture timer, you can call :cpp:func:`mcpwm_new_capture_timer` function, with configuration structure :cpp:type:`mcpwm_capture_timer_config_t` as the parameter. The configuration structure is defined as:
-:cpp:member:`mcpwm_capture_timer_config_t::group_id` sets the MCPWM group ID. The ID should belong to [0, :c:macro:`SOC_MCPWM_GROUPS` - 1] range.
-:cpp:member:`mcpwm_capture_timer_config_t::clk_src` sets the clock source of the capture timer.
The :cpp:func:`mcpwm_new_capture_timer` will return a pointer to the allocated capture timer object if the allocation succeeds. Otherwise, it will return error code. Specifically, when there are no free capture timer left in the MCPWM group, this function will return :c:macro:`ESP_ERR_NOT_FOUND` error. [1]_
Next, to allocate a capture channel, you can call :cpp:func:`mcpwm_new_capture_channel` function, with a capture timer handle and configuration structure :cpp:type:`mcpwm_capture_channel_config_t` as the parameter. The configuration structure is defined as:
-:cpp:member:`mcpwm_capture_channel_config_t::gpio_num` sets the GPIO number used by the capture channel.
-:cpp:member:`mcpwm_capture_channel_config_t::prescale` sets the prescaler of the input signal.
-:cpp:member:`mcpwm_capture_channel_config_t::pos_edge` and :cpp:member:`mcpwm_capture_channel_config_t::neg_edge` set whether to capture on the positive and/or negative edge of the input signal.
-:cpp:member:`mcpwm_capture_channel_config_t::pull_up` and :cpp:member:`mcpwm_capture_channel_config_t::pull_down` set whether to pull up and/or pull down the GPIO internally.
-:cpp:member:`mcpwm_capture_channel_config_t::invert_cap_signal` sets whether to invert the capture signal.
-:cpp:member:`mcpwm_capture_channel_config_t::io_loop_back` sets whether to enable the loop back mode. It is for debugging purposes only. It enables both the GPIO's input and output ability through the GPIO matrix peripheral.
The :cpp:func:`mcpwm_new_capture_channel` will return a pointer to the allocated capture channel object if the allocation succeeds. Otherwise, it will return error code. Specifically, when there are no free capture channel left in the capture timer, this function will return :c:macro:`ESP_ERR_NOT_FOUND` error.
On the contrary, calling :cpp:func:`mcpwm_del_capture_channel` and :cpp:func:`mcpwm_del_capture_timer` function will free the allocated capture channel and timer object accordingly.
Timer Operations and Events
^^^^^^^^^^^^^^^^^^^^^^^^^^^
Register Event Callbacks
~~~~~~~~~~~~~~~~~~~~~~~~
The MCPWM timer can generate different events at runtime. If you have some function that should be called when particular event happens, you should hook your function to the interrupt service routine by calling :cpp:func:`mcpwm_timer_register_event_callbacks`. The callback function prototype is declared in :cpp:type:`mcpwm_timer_event_cb_t`. All supported event callbacks are listed in the :cpp:type:`mcpwm_timer_event_callbacks_t`:
-:cpp:member:`mcpwm_timer_event_callbacks_t::on_full` sets callback function for timer when it counts to peak value.
-:cpp:member:`mcpwm_timer_event_callbacks_t::on_empty` sets callback function for timer when it counts to zero.
-:cpp:member:`mcpwm_timer_event_callbacks_t::on_stop` sets callback function for timer when it is stopped.
The callback functions above are called within the ISR context, so they should **not** attempt to block (e.g., make sure that only FreeRTOS APIs with ``ISR`` suffix is called within the function).
The parameter ``user_data`` of :cpp:func:`mcpwm_timer_register_event_callbacks` function is used to save user's own context, it will be passed to each callback function directly.
This function will lazy install interrupt service for the MCPWM timer without enabling it. It is only allowed to be called before :cpp:func:`mcpwm_timer_enable`, otherwise the :c:macro:`ESP_ERR_INVALID_STATE` error will be returned. See also `Enable and Disable timer <#enable-and-disable-timer>`__ for more information.
Before doing IO control to the timer, user needs to enable the timer first, by calling :cpp:func:`mcpwm_timer_enable`. Internally, this function will:
* switch the timer state from **init** to **enable**.
* enable the interrupt service if it has been lazy installed by :cpp:func:`mcpwm_timer_register_event_callbacks`.
* acquire a proper power management lock if a specific clock source (e.g. PLL_160M clock) is selected. See also `Power management <#power-management>`__ for more information.
On the contrary, calling :cpp:func:`mcpwm_timer_disable` will put the timer driver back to **init** state, disable the interrupts service and release the power management lock.
Start and Stop Timer
~~~~~~~~~~~~~~~~~~~~
The basic IO operation of a timer is to start and stop. Calling :cpp:func:`mcpwm_timer_start_stop` with different :cpp:type:`mcpwm_timer_start_stop_cmd_t` commands can start the timer immediately or stop the timer at a specific event. What're more, you can even start the timer for only one round, that means, the timer will count to peak value or zero, and then stop itself.
Connect Timer with Operator
~~~~~~~~~~~~~~~~~~~~~~~~~~~
The allocated MCPWM Timer should be connected with a MCPWM operator by calling :cpp:func:`mcpwm_operator_connect_timer`, so that the operator can take that timer as its time base, and generate the required PWM waves. Make sure the MCPWM timer and operator are in the same group, otherwise, this function will return :c:macro:`ESP_ERR_INVALID_ARG` error.
Comparator Operations and Events
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Register Event Callbacks
~~~~~~~~~~~~~~~~~~~~~~~~
The MCPWM comparator can inform the user when the timer counter equals to the compare value. If you have some function that should be called when this event happens, you should hook your function to the interrupt service routine by calling :cpp:func:`mcpwm_comparator_register_event_callbacks`. The callback function prototype is declared in :cpp:type:`mcpwm_compare_event_cb_t`. All supported event callbacks are listed in the :cpp:type:`mcpwm_comparator_event_callbacks_t`:
-:cpp:member:`mcpwm_comparator_event_callbacks_t::on_reach` sets callback function for comparator when the timer counter equals to the compare value.
The callback function will provide event specific data of type :cpp:type:`mcpwm_compare_event_data_t` to the user. The callback function is called within the ISR context, so is should **not** attempt to block (e.g., make sure that only FreeRTOS APIs with ``ISR`` suffix is called within the function).
The parameter ``user_data`` of :cpp:func:`mcpwm_comparator_register_event_callbacks` function is used to save user's own context, it will be passed to the callback function directly.
This function will lazy install interrupt service for the MCPWM comparator, whereas the service can only be removed in :cpp:type:`mcpwm_del_comparator`.
Set Compare Value
~~~~~~~~~~~~~~~~~
You can set the compare value for the MCPWM comparator at runtime by calling :cpp:func:`mcpwm_comparator_set_compare_value`. There're a few points to note:
- New compare value might won't take effect immediately. The update time for the compare value is set by :cpp:member:`mcpwm_comparator_config_t::update_cmp_on_tez` or :cpp:member:`mcpwm_comparator_config_t::update_cmp_on_tep` or :cpp:member:`mcpwm_comparator_config_t::update_cmp_on_sync`.
- Make sure the operator has connected to one MCPWM timer already by :cpp:func:`mcpwm_operator_connect_timer`. Otherwise, it will return error code :c:macro:`ESP_ERR_INVALID_STATE`.
- The compare value shouldn't exceed timer's count peak, otherwise, the compare event will never got triggered.
Generator Actions on Events
^^^^^^^^^^^^^^^^^^^^^^^^^^^
Set Generator Action on Timer Event
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
One generator can set multiple actions on different timer events, by calling :cpp:func:`mcpwm_generator_set_actions_on_timer_event` with variable number of action configurations. The action configuration is defined in :cpp:type:`mcpwm_gen_timer_event_action_t`:
-:cpp:member:`mcpwm_gen_timer_event_action_t::direction` specific the timer direction. The supported directions are listed in :cpp:type:`mcpwm_timer_direction_t`.
-:cpp:member:`mcpwm_gen_timer_event_action_t::event` specifies the timer event. The supported timer events are listed in :cpp:type:`mcpwm_timer_event_t`.
-:cpp:member:`mcpwm_gen_timer_event_action_t::action` specifies the generator action to be taken. The supported actions are listed in :cpp:type:`mcpwm_generator_action_t`.
There's a helper macro :c:macro:`MCPWM_GEN_TIMER_EVENT_ACTION` to simplify the construction of a timer event action entry.
Please note, the argument list of :cpp:func:`mcpwm_generator_set_actions_on_timer_event`**must** be terminated by :c:macro:`MCPWM_GEN_TIMER_EVENT_ACTION_END`.
One generator can set multiple actions on different compare events, by calling :cpp:func:`mcpwm_generator_set_actions_on_compare_event` with variable number of action configurations. The action configuration is defined in :cpp:type:`mcpwm_gen_compare_event_action_t`:
-:cpp:member:`mcpwm_gen_compare_event_action_t::direction` specific the timer direction. The supported directions are listed in :cpp:type:`mcpwm_timer_direction_t`.
-:cpp:member:`mcpwm_gen_compare_event_action_t::comparator` specifies the comparator handle. See `MCPWM Comparators <#mcpwm-comparators>`__ for how to allocate a comparator.
-:cpp:member:`mcpwm_gen_compare_event_action_t::action` specifies the generator action to be taken. The supported actions are listed in :cpp:type:`mcpwm_generator_action_t`.
There's a helper macro :c:macro:`MCPWM_GEN_COMPARE_EVENT_ACTION` to simplify the construction of a compare event action entry.
Please note, the argument list of :cpp:func:`mcpwm_generator_set_actions_on_compare_event`**must** be terminated by :c:macro:`MCPWM_GEN_COMPARE_EVENT_ACTION_END`.
This section will demonstrate the classical PWM waveforms that can be generated by the pair of the generators. The code snippet that is used to generate the waveforms is also provided below the diagram. Some general summary:
In power electronics, the rectifier and inverter are commonly used. This requires the use of rectifier bridge and inverter bridge. Each bridge arm has two power electronic devices, such as MOSFET, IGBT, etc. The two MOSFETs on the same arm can't conduct at the same time, otherwise there will be a short circuit. The fact is that, although the PWM wave shows it is turning off the switch, but the MOSFET still needs a small time window to make that happen. This requires an extra delay to be added to the existing PWM wave that generated by setting `Generator Actions on Events <#generator-actions-on-events>`__.
The dead time driver works like a *decorator*. This is also reflected in the function parameters of :cpp:func:`mcpwm_generator_set_dead_time`, where it takes the primary generator handle (``in_generator``), and returns a new generator (``out_generator``) after applying the dead time. Please note, if the ``out_generator`` and ``in_generator`` are the same, it means we are adding the time delay to the PWM waveform in an "in-place" fashion. In turn, if the ``out_generator`` and ``in_generator`` are different, it means we're deriving a new PWM waveform from the existing ``in_generator``.
Dead-time specific configuration is listed in the :cpp:type:`mcpwm_dead_time_config_t` structure:
-:cpp:member:`mcpwm_dead_time_config_t::posedge_delay_ticks` and :cpp:member:`mcpwm_dead_time_config_t::negedge_delay_ticks` set the number of ticks to delay the PWM waveform on the rising and falling edge. Specifically, setting both of them to zero means to bypass the dead-time module. The resolution of the dead-time tick is the same to the timer that is connected with the operator by :cpp:func:`mcpwm_operator_connect_timer`.
-:cpp:member:`mcpwm_dead_time_config_t::invert_output`: Whether to invert the signal after applying the dead-time, which can be used to control the delay edge polarity.
Due to the hardware limitation, one delay module (either `posedge delay` or `negedge delay`) can't be applied to multiple MCPWM generators at the same time. e.g. the following configuration is **invalid**:
However, you can apply `posedge delay` to generator A and `negedge delay` to generator B. You can also set both `posedge delay` and `negedge delay` for generator A, while letting generator B bypass the dead time module.
It is also possible to generate the required dead time by setting `Generator Actions on Events <#generator-actions-on-events>`__, especially by controlling edge placement using different comparators. However, if the more classical edge delay-based dead time with polarity control is required, then the dead-time submodule should be used.
Classical PWM Waveforms and Dead Time Configurations
This section will demonstrate the classical PWM waveforms that can be generated by the dead-time submodule. The code snippet that is used to generate the waveforms is also provided below the diagram.
The MCPWM operator has a carrier submodule that can be used if galvanic isolation from the motor driver is required (e.g. isolated digital power application) by passing the PWM output signals through transformers. Any of PWM output signals may be at 100% duty and not changing whenever motor is required to run steady at the full load. Coupling of non alternating signals with a transformer is problematic, so the signals are modulated by the carrier submodule to create an AC waveform, to make the coupling possible.
To configure the carrier submodule, you can call :cpp:func:`mcpwm_operator_apply_carrier`, and provide configuration structure :cpp:type:`mcpwm_carrier_config_t`:
-:cpp:member:`mcpwm_carrier_config_t::frequency_hz`: The carrier frequency in Hz.
-:cpp:member:`mcpwm_carrier_config_t::duty_cycle`: The duty cycle of the carrier. Note that, the supported choices of duty cycle are discrete, the driver will search the nearest one based the user configuration.
-:cpp:member:`mcpwm_carrier_config_t::first_pulse_duration_us`: The duration of the first pulse in microseconds. The resolution of the first pulse duration is determined by the carrier frequency you set in the :cpp:member:`mcpwm_carrier_config_t::frequency_hz`. The first pulse duration can't be zero, and it has to be at least one period of the carrier. A longer pulse width can help conduct the inductance quicker.
-:cpp:member:`mcpwm_carrier_config_t::invert_before_modulate` and :cpp:member:`mcpwm_carrier_config_t::invert_after_modulate`: Set whether to invert the carrier output before and after modulation.
Specifically, the carrier submodule can be disabled by calling :cpp:func:`mcpwm_operator_apply_carrier` with a ``NULL`` configuration.
Faults and Brake Actions
^^^^^^^^^^^^^^^^^^^^^^^^
The MCPWM operator is able to sense external signals with information about failure of the motor, the power driver or any other device connected. These failure signals are encapsulated into `MCPWM fault objects <#mcpwm-faults>`__.
The user should determine possible failure modes of the motor and what action should be performed on detection of particular fault, e.g. drive all outputs low for a brushed motor, or lock current state for a stepper motor, etc. As result of this action the motor should be put into a safe state to reduce likelihood of a damage caused by the fault.
Set Operator Brake Mode on Fault
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The way that MCPWM operator reacts to the fault is called **Brake**. The MCPWM operator can be configured to perform different brake modes for each fault object by calling :cpp:func:`mcpwm_operator_set_brake_on_fault`. Brake specific configuration is passed as a structure :cpp:type:`mcpwm_brake_config_t`:
-:cpp:member:`mcpwm_brake_config_t::fault` set which fault that the operator should react to.
-:cpp:member:`mcpwm_brake_config_t::brake_mode` set the brake mode that should be used for the fault. The supported brake modes are listed in the :cpp:type:`mcpwm_operator_brake_mode_t`. For :cpp:enumerator:`MCPWM_OPER_BRAKE_MODE_CBC` mode, the operator will recover itself automatically as long as the fault disappears. You can specify the recovery time in :cpp:member:`mcpwm_brake_config_t::cbc_recover_on_tez` and :cpp:member:`mcpwm_brake_config_t::cbc_recover_on_tep`. For :cpp:enumerator:`MCPWM_OPER_BRAKE_MODE_OST` mode, the operator can't recover even though the fault disappears. User has to call :cpp:func:`mcpwm_operator_recover_from_fault` to manually recover it.
Set Generator Action on Brake Event
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
One generator can set multiple actions on different brake events, by calling :cpp:func:`mcpwm_generator_set_actions_on_brake_event` with variable number of action configurations. The action configuration is defined in :cpp:type:`mcpwm_gen_brake_event_action_t`:
-:cpp:member:`mcpwm_gen_brake_event_action_t::direction` specific the timer direction. The supported directions are listed in :cpp:type:`mcpwm_timer_direction_t`.
-:cpp:member:`mcpwm_gen_brake_event_action_t::brake_mode` specifies the brake mode. The supported brake modes are listed in the :cpp:type:`mcpwm_operator_brake_mode_t`.
-:cpp:member:`mcpwm_gen_brake_event_action_t::action` specifies the generator action to be taken. The supported actions are listed in :cpp:type:`mcpwm_generator_action_t`.
There's a helper macro :c:macro:`MCPWM_GEN_BRAKE_EVENT_ACTION` to simplify the construction of a brake event action entry.
Please note, the argument list of :cpp:func:`mcpwm_generator_set_actions_on_brake_event`**must** be terminated by :c:macro:`MCPWM_GEN_BRAKE_EVENT_ACTION_END`.
The MCPWM fault detector can inform the user when it detects a valid fault or a fault signal disappears. If you have some function that should be called when such event happens, you should hook your function to the interrupt service routine by calling :cpp:func:`mcpwm_fault_register_event_callbacks`. The callback function prototype is declared in :cpp:type:`mcpwm_fault_event_cb_t`. All supported event callbacks are listed in the :cpp:type:`mcpwm_fault_event_callbacks_t`:
-:cpp:member:`mcpwm_fault_event_callbacks_t::on_fault_enter` sets callback function that will be called when a fault is detected.
-:cpp:member:`mcpwm_fault_event_callbacks_t::on_fault_exit` sets callback function that will be called when a fault is cleared.
The callback function is called within the ISR context, so is should **not** attempt to block (e.g., make sure that only FreeRTOS APIs with ``ISR`` suffix is called within the function).
The parameter ``user_data`` of :cpp:func:`mcpwm_fault_register_event_callbacks` function is used to save user's own context, it will be passed to the callback function directly.
This function will lazy install interrupt service for the MCPWM fault, whereas the service can only be removed in :cpp:type:`mcpwm_del_fault`.
Register Brake Event Callbacks
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The MCPWM operator can inform the user when it going to take a brake action. If you have some function that should be called when this event happens, you should hook your function to the interrupt service routine by calling :cpp:func:`mcpwm_operator_register_event_callbacks`. The callback function prototype is declared in :cpp:type:`mcpwm_brake_event_cb_t`. All supported event callbacks are listed in the :cpp:type:`mcpwm_operator_event_callbacks_t`:
-:cpp:member:`mcpwm_operator_event_callbacks_t::on_brake_cbc` sets callback function that will be called when the operator is going to take a *CBC* action.
-:cpp:member:`mcpwm_operator_event_callbacks_t::on_brake_ost` sets callback function that will be called when the operator is going to take an *OST* action.
The callback function is called within the ISR context, so is should **not** attempt to block (e.g., make sure that only FreeRTOS APIs with ``ISR`` suffix is called within the function).
The parameter ``user_data`` of :cpp:func:`mcpwm_operator_register_event_callbacks` function is used to save user's own context, it will be passed to the callback function directly.
This function will lazy install interrupt service for the MCPWM operator, whereas the service can only be removed in :cpp:type:`mcpwm_del_operator`.
Generator Force Actions
^^^^^^^^^^^^^^^^^^^^^^^
Software can override generator output level at runtime, by calling :cpp:func:`mcpwm_generator_set_force_level`. The software force level always has a higher priority than other event actions set in e.g. :cpp:func:`mcpwm_generator_set_actions_on_timer_event`.
- Set the ``level`` to -1 means to disable the force action, and the generator's output level will be controlled by the event actions again.
- Set the ``hold_on`` to true, the force output level will keep alive, until it's removed by assigning ``level`` to -1.
- Set the ``hole_on`` to false, the force output level will only be active for a short time, any upcoming event can override it.
Synchronization
^^^^^^^^^^^^^^^
When a sync signal is taken by the MCPWM timer, the timer will be forced into a predefined **phase**, where the phase is determined by count value and count direction. You can set the sync phase by calling :cpp:func:`mcpwm_timer_set_phase_on_sync`. The sync phase configuration is defined in :cpp:type:`mcpwm_timer_sync_phase_config_t` structure:
-:cpp:member:`mcpwm_timer_sync_phase_config_t::sync_src` sets the sync signal source. See `MCPWM Sync Sources <#mcpwm-sync-sources>`__ for how to create a sync source object. Specifically, if this is set to ``NULL``, the driver will disable the sync feature for the MCPWM timer.
-:cpp:member:`mcpwm_timer_sync_phase_config_t::count_value` sets the count value to load when the sync signal is taken.
-:cpp:member:`mcpwm_timer_sync_phase_config_t::direction` sets the count direction when the sync signal is taken.
Likewise, the MCPWM capture timer `MCPWM Capture Timer <#mcpwm-capture-timer-and-channels>`__ can be synced as well. You can set the sync phase for the capture timer by calling :cpp:func:`mcpwm_capture_timer_set_phase_on_sync`. The sync phase configuration is defined in :cpp:type:`mcpwm_capture_timer_sync_phase_config_t` structure:
-:cpp:member:`mcpwm_capture_timer_sync_phase_config_t::sync_src` sets the sync signal source. See `MCPWM Sync Sources <#mcpwm-sync-sources>`__ for how to create a sync source object. Specifically, if this is set to ``NULL``, the driver will disable the sync feature for the MCPWM capture timer.
-:cpp:member:`mcpwm_capture_timer_sync_phase_config_t::count_value` sets the count value to load when the sync signal is taken.
-:cpp:member:`mcpwm_capture_timer_sync_phase_config_t::direction` sets the count direction when the sync signal is taken. Note that, different from MCPWM Timer, the capture timer can only support one count direction: :cpp:enumerator:`MCPWM_TIMER_DIRECTION_UP`.
The basic functionality of MCPWM capture is to record the time when any pulse edge of the capture signal turns active. Then you can get the pulse width and convert it into other physical quantity like distance or speed in the capture callback function. For example, in the BLDC (Brushless DC, see figure below) scenario, we can use the capture submodule to sense the rotor position from Hall sensor.
The capture timer is usually connected with several capture channels, please refer to `MCPWM Capture Timer and Channels <#mcpwm-capture-timer-and-channels>`__ for resource allocation.
The MCPWM capture channel can inform the user when there's a valid edge detected on the signal. You have to register a callback function to get the timer count value of the capture moment, by calling :cpp:func:`mcpwm_capture_channel_register_event_callbacks`. The callback function prototype is declared in :cpp:type:`mcpwm_capture_event_cb_t`. All supported capture callbacks are listed in the :cpp:type:`mcpwm_capture_event_callbacks_t`:
The callback function will provide event specific data of type :cpp:type:`mcpwm_capture_event_data_t`, so that you can get the edge of the capture signal in :cpp:member:`mcpwm_capture_event_data_t::cap_edge` and the count value of that moment in :cpp:member:`mcpwm_capture_event_data_t::cap_value`. To convert the capture count into timestamp, you need to know the resolution of the capture timer by calling :cpp:func:`mcpwm_capture_timer_get_resolution`.
The callback function is called within the ISR context, so is should **not** attempt to block (e.g., make sure that only FreeRTOS APIs with ``ISR`` suffix is called within the function).
The parameter ``user_data`` of :cpp:func:`mcpwm_capture_channel_register_event_callbacks` function is used to save user's own context, it will be passed to the callback function directly.
This function will lazy install interrupt service for the MCPWM capture channel, whereas the service can only be removed in :cpp:type:`mcpwm_del_capture_channel`.
The capture channel is not enabled after allocation by :cpp:func:`mcpwm_new_capture_channel`. You should call :cpp:func:`mcpwm_capture_channel_enable` and :cpp:func:`mcpwm_capture_channel_disable` accordingly to enable or disable the channel. If the interrupt service is lazy installed during registering event callbacks for the channel in :cpp:func:`mcpwm_capture_channel_register_event_callbacks`, :cpp:func:`mcpwm_capture_channel_enable` will enable the interrupt service as well.
Before doing IO control to the capture timer, user needs to enable the timer first, by calling :cpp:func:`mcpwm_capture_timer_enable`. Internally, this function will:
* switch the capture timer state from **init** to **enable**.
* acquire a proper power management lock if a specific clock source (e.g. APB clock) is selected. See also `Power management <#power-management>`__ for more information.
On the contrary, calling :cpp:func:`mcpwm_capture_timer_disable` will put the timer driver back to **init** state, and release the power management lock.
The basic IO operation of a capture timer is to start and stop. Calling :cpp:func:`mcpwm_capture_timer_start` can start the timer and calling :cpp:func:`mcpwm_capture_timer_stop` can stop the timer immediately.
Sometime, the software also wants to trigger a "fake" capture event. The :cpp:func:`mcpwm_capture_channel_trigger_soft_catch` is provided for that purpose. Please note that, even though it's a "fake" capture event, it can still cause an interrupt, thus your capture event callback function will get invoked as well.
When power management is enabled (i.e. :ref:`CONFIG_PM_ENABLE` is on), the system will adjust the PLL, APB frequency before going into light sleep, thus potentially changing the period of a MCPWM timers' counting step and leading to inaccurate time keeping.
However, the driver can prevent the system from changing APB frequency by acquiring a power management lock of type :cpp:enumerator:`ESP_PM_APB_FREQ_MAX`. Whenever the driver creates a MCPWM timer instance that has selected :cpp:enumerator:`MCPWM_TIMER_CLK_SRC_PLL160M` as its clock source, the driver will guarantee that the power management lock is acquired when enable the timer by :cpp:func:`mcpwm_timer_enable`. Likewise, the driver releases the lock when :cpp:func:`mcpwm_timer_disable` is called for that timer.
Likewise, Whenever the driver creates a MCPWM capture timer instance that has selected :cpp:enumerator:`MCPWM_CAPTURE_CLK_SRC_APB` as its clock source, the driver will guarantee that the power management lock is acquired when enable the timer by :cpp:func:`mcpwm_capture_timer_enable`. And will release the lock in :cpp:func:`mcpwm_capture_timer_disable`.
By default, the MCPWM interrupt will be deferred when the Cache is disabled for reasons like writing/erasing Flash. Thus the event callback functions will not get executed in time, which is not expected in a real-time application.
There is another Kconfig option :ref:`CONFIG_MCPWM_CTRL_FUNC_IN_IRAM` that can put commonly used IO control functions into IRAM as well. So, these functions can also be executable when the cache is disabled. These IO control functions are as follows:
The factory functions like :cpp:func:`mcpwm_new_timer` are guaranteed to be thread safe by the driver, which means, you can call it from different RTOS tasks without protection by extra locks.
The following functions are allowed to run under ISR context, as the driver uses a critical section to prevent them being called concurrently in the task and ISR.
Other functions that are not related to `Resource Allocation <#resource-allocation-and-initialization>`__, are not thread safe. Thus, you should avoid calling them in different tasks without mutex protection.
-:ref:`CONFIG_MCPWM_ISR_IRAM_SAFE` controls whether the default ISR handler can work when cache is disabled, see `IRAM Safe <#iram-safe>`__ for more information.
-:ref:`CONFIG_MCPWM_CTRL_FUNC_IN_IRAM` controls where to place the MCPWM control functions (IRAM or flash), see `IRAM Safe <#iram-safe>`__ for more information.
Different ESP chip series might have different number of MCPWM resources (e.g. groups, timers, comparators, operators, generators and so on). Please refer to the [`TRM <{IDF_TARGET_TRM_EN_URL}#mcpwm>`__] for details. The driver won't forbid you from applying for more MCPWM resources, but it will return error when there's no hardware resources available. Please always check the return value when doing `Resource Allocation <#resource-allocation-and-initialization>`__.
