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ESP32: rtc_gpio_hold_en() called on non-RTC GPIO18 during LilyGO repeater shutdown

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Assessment

Difficulty
3/5
Estimated time
1-2 days
Newbie friendliness
55/100
Issue type
Bug
Clarity
Mostly clear
Activity status
Active
Tech stack
c
Domain
embedded-iot

Research direction

Read src/helpers/ESP32Board.cpp and variants/lilygo_tlora_v2_1/platformio.ini to trace ESP32Board::enterDeepSleep() and confirm the NSS pin definition. Check the ESP-IDF GPIO documentation for the hold API supported by the target ESP32 variant. Done means deep sleep no longer calls an RTC-only API for GPIO18; verify the behavior on the affected hardware if available.

Written by the indexing model from the issue text.

Description

While helping another user troubleshoot a LilyGO LoRa32 V2.1-1.6 repeater (ESP32, 433 MHz variant), I came across an invalid RTC GPIO call in the deep-sleep code.

Observed behavior

A custom Repeater build based on commit a366955cb2f67b8e6842d4f00d2b6a554dddd88a booted successfully, then entered the power-off sequence and produced this log:

Repeater ID: <redacted>
Powering Off
E (5387) RTCIO: rtc_gpio_hold_en(153): RTCIO number error

The build used a different radio frequency and LoRa reset pin, but the NSS pin definition and deep-sleep implementation were unchanged from upstream.

Cause

The LilyGO profile defines:

-D P_LORA_NSS=18

On the original ESP32, ESP32Board::enterDeepSleep() calls:

rtc_gpio_hold_en((gpio_num_t)P_LORA_NSS);

GPIO18 is not RTC-capable on the original ESP32, so rtc_gpio_hold_en() returns ESP_ERR_INVALID_ARG.

The 153 in the error message is an ESP-IDF source line number, not a GPIO number.

The call is also present in the current upstream main branch.

Expected behavior

The deep-sleep code should not call an RTC-only API for a regular GPIO.

If keeping NSS high during deep sleep is required, the appropriate GPIO hold mechanism should be used for the target ESP32 variant.

Scope of testing

I traced the shutdown path in the source and checked it against the captured UART log.

The power-off event itself appears to originate from the GPIO0 long-press handler. Its electrical cause has not been established.

The invalid RTC GPIO call explains the subsequent RTCIO error, not the original power-off event.

I have not reproduced this on an unmodified stock firmware binary or verified a fix on the affected hardware.

References
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