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soc/rtc_clk: fix loss of precision in estimation of XTAL frequency

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RTC_FAST_CLK_FREQ_APPROX is defined as 8500000, so 0.5MHz part was lost
when dividing by MHZ. Since cal_val is 64-bit the parens can be removed.

With 40MHz XTAL for a nominal ESP32 chip, this fixes estimated XTAL
frequency from 38 to 40MHz.
This commit is contained in:
Ivan Grokhotkov 2018-01-08 23:31:21 +08:00
parent 0cd97cecb2
commit 7c584e80b0
1 changed files with 1 additions and 1 deletions
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2
components/soc/esp32/rtc_clk.c
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@ -589,7 +589,7 @@ static rtc_xtal_freq_t rtc_clk_xtal_freq_estimate()
* (shifted by RTC_CLK_CAL_FRACT bits).
* Xtal frequency will be (cal_val * 8M / 256) / 2^19
*/
uint32_t freq_mhz = (cal_val * (RTC_FAST_CLK_FREQ_APPROX / MHZ) / 256 ) >> RTC_CLK_CAL_FRACT;
uint32_t freq_mhz = (cal_val * RTC_FAST_CLK_FREQ_APPROX / MHZ / 256 ) >> RTC_CLK_CAL_FRACT;
/* Guess the XTAL type. For now, only 40 and 26MHz are supported.
*/
switch (freq_mhz) {