What does this implement/fix?

The max_glitch_ns calculation used 1000000 (10^6) instead of 10^9 when converting PCNT_LL_MAX_GLITCH_WIDTH ticks to nanoseconds. This made the computed maximum 1000x too small (12ns instead of 12787ns), causing std::min to cap the user's requested filter (e.g. 13000ns for 13µs) to just 12ns. ESP-IDF then converts that to 0 APB clock cycles — effectively disabling the glitch filter entirely.

With the filter disabled, the PCNT hardware counts electrical noise as pulses, producing wildly inflated readings (e.g. ~280,000 pulses/min instead of ~1,010 on an ESP32-C6).

This fix uses the same split-division approach as ESP-IDF's own pulse_cnt.c:404 to stay in 32-bit arithmetic:

// ESP-IDF (ns → cycles): cycles = (freq / 1000000) * ns / 1000
// ESPHome (cycles → ns): ns     = cycles * 1000 / (freq / 1000000)

Types of changes

• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Developer breaking change (an API change that could break external components)
• Code quality improvements to existing code or addition of tests
• Other

Related issue or feature (if applicable):

• fixes Compile error with pulse_counter #14069

Pull request in esphome-docs with documentation (if applicable):

• N/A

Test Environment

• ESP32
• ESP32 IDF
• ESP8266
• RP2040
• BK72xx
• RTL87xx
• LN882x
• nRF52840

Example entry for config.yaml:

sensor:
  - platform: pulse_counter
    pin: GPIO18
    name: "Pulse Counter"
    internal_filter: 13us

Checklist:

• The code change is tested and works locally.
• Tests have been added to verify that the new code works (under tests/ folder).

If user exposed functionality or configuration variables are added/changed:

• Documentation added/updated in esphome-docs.