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5b54ae76d4
When ESP32-C2 is paired with a 26 MHz XTAL, the systimer tick
frequency becomes equal to 26 / 2.5 = 10.4 MHz. Previously we always
assumed that systimer tick frequency is integer (and 1 MHz * power of
two, above that!).
This commit introduces a new LL macro, SYSTIMER_LL_TICKS_PER_US_DIV.
It should be set in such a way that:
1. SYSTIMER_LL_TICKS_PER_US / SYSTIMER_LL_TICKS_PER_US_DIV equals the
actual systimer tick frequency,
2. and SYSTIMER_LL_TICKS_PER_US is integer.
For ESP32-C2 this means that SYSTIMER_LL_TICKS_PER_US = 52 and
SYSTIMER_LL_TICKS_PER_US_DIV = 5.
This introduced two possible issues:
1. Overflow when multiplying systimer counter by 5
- Should not be an issue, since systimer counter is 52-bit, so
counter * 5 is no more than 55-bit.
2. The code needs to perform:
- divide by 5: when converting from microseconds to ticks
- divide by 52: when converting from ticks to microseconds
The latter potentially introduces a performance issue for the
esp_timer_get_time function.
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| .. | ||
| include | ||
| ld | ||
| adc_periph.c | ||
| CMakeLists.txt | ||
| dedic_gpio_periph.c | ||
| gdma_periph.c | ||
| gpio_periph.c | ||
| i2c_bias.h | ||
| i2c_periph.c | ||
| i2c_pmu.h | ||
| i2c_ulp.h | ||
| i2s_periph.c | ||
| interrupts.c | ||
| ledc_periph.c | ||
| rmt_periph.c | ||
| sigmadelta_periph.c | ||
| spi_periph.c | ||
| temperature_sensor_periph.c | ||
| timer_periph.c | ||
| uart_periph.c | ||