Are MCPWM capture callbacks available?

Projects Programming
1

Using #include "driver/mcpwm_cap.h" in the Espressif ESP-IDF we can register callbacks for the capture events e.g.

mcpwm_capture_channel_register_event_callbacks()

Unlike using hardware interrupts, the MCPWM capture module can freeze a timer count with zero latency.

As far as I can tell, the Arduino framework has no equivalent in the MCPWM related library i.e. capture callbacks aren't provided by #include "driver/mcpwm.h"

Have I hit a brick wall with using the Arduino IDE for my project which requires three channels of microsecond accuracy pulse-width measurement or am I missing some information about using this module (I'm only aware of one source of documentation i.e. peripherals api-reference from espressif).

2

Perhaps someone could help me understand how the Arduino ESP32 libraries are managed?

The source for the mcpwm.h file appears to be held in the espressif/arduino-esp32/repo commited by me-no-dev around 6 years ago. I'm not familiar with the history of the Arduino framework - is it no longer maintained?

3

Looking in that file, it appears that you specify the callback function in a 'mcpwm_capture_config_t' struct:

/**
 * @brief MCPWM config capture structure
 */
typedef struct {
    mcpwm_capture_on_edge_t cap_edge;      /*!<Set capture edge*/
    uint32_t cap_prescale;                 /*!<Prescale of capture signal, ranging from 1 to 256*/
    cap_isr_cb_t capture_cb;               /*!<User defined capture event callback, running under interrupt context */
    void *user_data;                       /*!<User defined ISR callback function args*/
} mcpwm_capture_config_t;

And then register it with this function:

/**
 * @brief Enable capture channel
 *
 * @param mcpwm_num set MCPWM unit(0-1)
 * @param cap_channel capture channel, which needs to be enabled
 * @param cap_conf capture channel configuration
 *
 * @return
 *     - ESP_OK Success
 *     - ESP_ERR_INVALID_ARG Parameter error
 */
esp_err_t mcpwm_capture_enable_channel(mcpwm_unit_t mcpwm_num, mcpwm_capture_channel_id_t cap_channel, const mcpwm_capture_config_t *cap_conf);
4

Which file? As far as I can tell, the arduino-esp32 driver is located at:

Which has been loaded by my Arduino IDE library manager to:

C:\Users\xxxxxx\AppData\Local\Arduino15\packages\esp32\hardware\esp32\1.0.6\tools\sdk\include\driver\driver\mcpwm.h

and searching through that file, there is no occurrence of the structure mcpwm_capture_config_t or the function mcpwm_capture_enable_channel() Have I got the wrong library? I had updated the IDE recently.

Some of the confusion I think comes from the overhaul of the ESP-IDF drivers to version 5. These most recent drivers became incompatible with some legacy calls from version 4.x
I have no idea what version the Arduino libraries are based on but the driver that is
loaded by it has no facility for callback on capture event.

5

Did you try looking at the version of 'mcpwm.h' that's installed on your PC and not just at the GitHub? What version of the ESP32 Arduino Core are you using? I have v2.0.14 that's based on ESP-IDF v4.4.6. It's the most recent version that's not in an Alpha state. In that version, 'mcpwm.h' contains the struct definition and function prototype that I cited.

6

When I check the boards manager for my dev board it says version 1.0.6. but It's also offering to upgrade to 2.0.11 however that fails as follows:

Configuring tool.
arduino:dfu-util@0.11.0-arduino5 installed
Replacing platform esp32:esp32@1.0.6 with esp32:esp32@2.0.11
Uninstalling esp32:esp32@1.0.6
Error upgrading platform: removing platform files: remove C:\Users\adria_000\AppData\Local\Arduino15\packages\esp32\hardware\esp32\1.0.6\tools\sdk\include\driver\driver: The process cannot access the file because it is being used by another process.
Uninstalling esp32:esp32@2.0.11
Platform esp32:esp32@2.0.11 uninstalled
Failed to install platform: 'esp32:esp32:2.0.11'.
Error: 13 INTERNAL: Cannot upgrade platform: removing platform files: remove C:\Users\adria_000\AppData\Local\Arduino15\packages\esp32\hardware\esp32\1.0.6\tools\sdk\include\driver\driver: The process cannot access the file because it is being used by another process.
7

v1.0.6 is almost 3 years old. That being said, did you actually look inside 'mcpwm.h' for your installation as I advised? Did it have any provisions for callbacks?

I can't help you with the upgrade problem. Toolchain issues aren't my forte.

8

Thanks for your help. I reinstalled the arduino IDE and managed to install the most recent library (esp32 by Espressif 2.0.11) I now have the callback control block you outlined although the code example I have taken from the ESP-IDF still isn't compatible. I have to start work converting it over now.

Actually my preferred IDE is platformio in VS code using the arduino framework. This, however, has the same incompatibility. I wonder why the arduino framework has a very different structure - merging the capture callbacks into the driver/mcpwm.h file - whereas the ESP-IDF has a a separate driver/mcpwm_cap.h for the capture stuff?

9

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