esp_io_expander: how to use with APIs with GPIO number parameter

[dmartauz]

Related area

esp_io_expander

Hardware specification

custom ESP32-P4 board

Is your feature request related to a problem?

In our application with ESP32-P4 as main host we need to use IO expander due to lack of GPIOs. We would like to use it for slow and rarely used signals such as RESET pins of external circuits, BOOT pins of external RCPs, etc.

Example - we would like to connect RESET pin of external Ethernet PHY to an IO expander.
https://docs.espressif.com/projects/esp-idf/en/latest/esp32p4/api-reference/network/esp_eth.html#create-mac-and-phy-instance
phy_config.reset_gpio_num = CONFIG_EXAMPLE_ETH_PHY_RST_GPIO; // alter the GPIO used for PHY reset
eth_phy_config_t struct does not allow to define callbacks, only GPIO pin number.

Describe the solution you'd like

It is possible to set pin number parameter to -1 and handle RESET pin of Ethernet PHY outside of Ethernet API but it would be better if GPIOs provided by IO expander could be used the same way as native GPIOs available on the SoC.

Describe alternatives you've considered

No response

Additional context

No response

I have checked existing list of Feature requests and the Contribution Guide

• I confirm I have checked existing list of Feature requests and Contribution Guide.

[github-actions]

Hi @dmartauz! Please be aware that (1) the following suggestions are generated by a bot and haven't been fact-checked by Espressif Systems, (2) burning eFuses and enabling security features are irreversible operations and can damage your ESP32 device. We hope that this message will help you until an Espressif Engineer looks at your issue.

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Thank you for your detailed question regarding the use of IO expander GPIOs with the ESP-IDF Ethernet API, specifically for controlling signals like the Ethernet PHY reset pin on an ESP32-P4 board.

Based on the available Espressif documentation, the Ethernet driver’s configuration structures (such as eth_phy_config_t) only accept native SoC GPIO numbers for parameters like reset_gpio_num. There is currently no built-in support in ESP-IDF to use GPIOs provided by an IO expander in place of native SoC GPIOs for these APIs. The APIs expect a standard GPIO number, and there is no mechanism to register callbacks or abstract the reset operation to an external handler or expander pin. Setting the pin number to -1 disables hardware reset, as you noted, but then you must handle the reset logic externally in your application code ESP-IDF Ethernet API Reference.

Summary of current options:

• Native GPIO only: The Ethernet driver expects a native GPIO number for reset and similar signals.
• Workaround: Set reset_gpio_num = -1 and manually control the reset pin via the IO expander in your application logic, outside the Ethernet driver.
• No callback/abstraction support: There is no API to register a callback or custom handler for these signals using an IO expander.

Feature request validity:
Your suggestion to allow the use of IO expander GPIOs in place of native GPIOs (or to allow a callback mechanism) is valid and would be a useful enhancement for applications with high GPIO demand. However, as of now, this is not supported by the ESP-IDF or the esp_io_expander component.

References:

• ESP-IDF Ethernet API: Create MAC and PHY Instance
• esp_io_expander component usage

Recommendation:
For now, you will need to manage the IO expander-controlled signals (like PHY reset) in your application code, ensuring the correct sequence before/after Ethernet driver initialization. If you require tighter integration, consider submitting a feature request to Espressif for future releases.

If you need example code for controlling an IO expander pin in ESP-IDF, let me know!