MCPWM ETM：外设间的硬件级联动

事件任务矩阵（ETM）可将 MCPWM 定时器或比较器事件直接路由到 ETM 任务，避免 ISR 延迟。适用于其他外设必须在精确 PWM 相位响应的场景。

先从定时器或比较器创建 ETM 事件，再创建目标外设的兼容任务，最后通过 ETM 通道连接两者。目标外设驱动文档定义了其任务和完整通道配置。关于 ETM 的整体用法——分配通道、把事件连接到任务——请参阅 ETM 文档。

        flowchart LR
    T["MCPWM 定时器<br/>TEZ/TEP 事件"]:::source --> E["ETM 通道"]:::route
    C["MCPWM 比较器<br/>比较事件"]:::source --> E
    E --> D["目标<br/>外设任务"]:::dest
    classDef source fill:#dbeafe,stroke:#2563eb,color:#172554
    classDef route fill:#ede9fe,stroke:#7c3aed,color:#2e1065
    classDef dest fill:#dcfce7,stroke:#16a34a,color:#14532d

定时器会产生 TEZ （定时器归零）或 TEP （定时器到达峰值）事件。要获取一个事件：

esp_etm_event_handle_t timer_event = NULL;
ESP_ERROR_CHECK(mcpwm_timer_new_etm_event(timer,
    &(mcpwm_timer_etm_event_config_t) {
        .event_type = MCPWM_TIMER_ETM_EVENT_TEZ,
    }, &timer_event));
// 创建目标 ETM task、分配 channel，然后连接：
// esp_etm_channel_connect(channel, timer_event, destination_task);

比较器提供 EQUAL 事件，每当定时器计数值等于比较器取值时触发。它能把事件固定到 PWM 周期中的任意相位，而不只是波峰或波谷。要获取一个事件：

esp_etm_event_handle_t cmp_event = NULL;
ESP_ERROR_CHECK(mcpwm_comparator_new_etm_event(cmp,
    &(mcpwm_cmpr_etm_event_config_t) {
        .event_type = MCPWM_CMPR_ETM_EVENT_EQUAL,
    }, &cmp_event));
// esp_etm_channel_connect(channel, cmp_event, destination_task);

使用完毕后调用 esp_etm_del_event() 释放事件。

比较器事件一个非常常见的用途是触发 ADC 采样：把比较器设置在想要采样的相位点，再由比较器事件启动 ADC，使转换器在与 PWM 周期精确同步的相位点采样稳定、干净的波形。由于整条链路完全由硬件完成，采样点能无 CPU 参与、无 ISR 延迟地跟随 PWM。

API 参考

MCPWM ETM 驱动函数

Header File

  • components/esp_driver_mcpwm/include/driver/mcpwm_etm.h

  • This header file can be included with:

    #include "driver/mcpwm_etm.h"

  • This header file is a part of the API provided by the esp_driver_mcpwm component. To declare that your component depends on esp_driver_mcpwm, add the following to your CMakeLists.txt:

    REQUIRES esp_driver_mcpwm

    or

    PRIV_REQUIRES esp_driver_mcpwm

Functions

esp_err_t mcpwm_comparator_new_etm_event(mcpwm_cmpr_handle_t cmpr, const mcpwm_cmpr_etm_event_config_t *config, esp_etm_event_handle_t *out_event)

Get the ETM event for MCPWM comparator.

备注

The created ETM event object can be deleted later by calling esp_etm_del_event

参数:

  • cmpr -- [in] MCPWM comparator, allocated by mcpwm_new_comparator() or mcpwm_new_event_comparator()

  • config -- [in] MCPWM ETM comparator event configuration

  • out_event -- [out] Returned ETM event handle

返回:

  • ESP_OK: Get ETM event successfully

  • ESP_ERR_INVALID_ARG: Get ETM event failed because of invalid argument

  • ESP_FAIL: Get ETM event failed because of other error

esp_err_t mcpwm_timer_new_etm_event(mcpwm_timer_handle_t timer, const mcpwm_timer_etm_event_config_t *config, esp_etm_event_handle_t *out_event)

Get the ETM event for MCPWM timer.

备注

The created ETM event object can be deleted later by calling esp_etm_del_event

参数:

  • timer -- [in] MCPWM timer, allocated by mcpwm_new_timer()

  • config -- [in] MCPWM ETM timer event configuration

  • out_event -- [out] Returned ETM event handle

返回:

  • ESP_OK: Get ETM event successfully

  • ESP_ERR_INVALID_ARG: Get ETM event failed because of invalid argument

  • ESP_FAIL: Get ETM event failed because of other error

Structures

struct mcpwm_cmpr_etm_event_config_t

MCPWM event comparator ETM event configuration.

Public Members

mcpwm_comparator_etm_event_type_t event_type

MCPWM comparator ETM event type

struct mcpwm_timer_etm_event_config_t

MCPWM timer ETM event configuration.

Public Members

mcpwm_timer_etm_event_type_t event_type

MCPWM timer ETM event type

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