QUERY · ISSUE

ESP32_C3： timer_group: timer_init(271): HW TIMER NUM ERROR

openby iBoundaryopened 2022-10-19updated 2026-03-19

bugport-esp32

from machine import*
tim = Timer(-1)
tim.init(period=1000,callback = lambda t:print('rtos'))
E (6078630) timer_group: timer_init(271): HW TIMER NUM ERROR
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
OSError: (-258, 'ESP_ERR_INVALID_ARG')

I found out that virtual timer is not available in ESP32_C3 chip.

CANDIDATE · ISSUE

esp32: Virtual timers not currently supported in doc

closedby jejopened 2021-02-26updated 2021-03-04

According to this page: http://docs.micropython.org/en/latest/esp32/quickref.html#timers virtual timers are not supported.
But it seems to work in real life with a -1 timer.
Is it a problem of documentation update?

from machine import Timer

t = Timer(-1)
t.init(period=1000, mode=Timer.PERIODIC, callback=lambda t:print("Working"))

while True:
    pass

Working
Working
Working
...

Assessment

Q Qwen · high

Both issues concern virtual timers (Timer(-1)) on ESP32, but they describe opposite situations. Issue #9674 reports that virtual timers FAIL on ESP32_C3 with a hardware timer error, while issue #6967 reports that virtual timers WORK on some ESP32 variants despite documentation saying they don't. These are related topics about the same feature but represent different chip-specific behaviors (C3 vs other ESP32 variants) and different root causes. The candidate does not resolve the query; it provides context about virtual timer support varying across ESP32 chips.

Suggested action

Keep both issues open. The candidate issue provides useful context about virtual timer support varying by ESP32 variant, which helps explain why #9674 fails on C3 but works elsewhere. Consider adding a note to #9674 referencing #6967 to document the chip-specific behavior.

ESP32_C3： timer_group: timer_init(271): HW TIMER NUM ERROR

esp32: Virtual timers not currently supported in doc

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