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usb_serial_jtag: fixed the docs that we can use usj in sleep modes

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Related to: https://github.com/espressif/esp-idf/issues/8507, https://github.com/espressif/esp-idf/issues/8884
This commit is contained in:
Michael (XIAO Xufeng)
2022-09-12 03:18:04 +08:00
parent 16dbb8f249
commit a0bf87ee5d
2 changed files with 31 additions and 7 deletions
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components/esp_hw_support/Kconfig
+18 -6
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@@ -114,12 +114,24 @@ menu "Hardware Settings"
depends on ESP_CONSOLE_USB_SERIAL_JTAG || ESP_CONSOLE_SECONDARY_USB_SERIAL_JTAG
default y
help
When the chip goes sleep or software reset, the clock source would change to XTAL
and switch off the BBPLL clock for saving power. However, this might make the
USB_SERIAL_JTAG down which depends on BBPLL as its unique clock source.
Therefore, this is used for keeping bbpll clock always on when USB_SERIAL_JTAG PORT is using.
If you want to use USB_SERIAL_JTAG under sw_reset case or sleep-wakeup case, you shoule select
this option. But be aware that this might increase the power consumption.
When software switches the CPU clock source from BBPLL clock to XTAL, usually the BBPLL will be
switched off. This helps to save some power consumption in sleep modes. However this may also happen
during the software reset, resulting in the inactive (disconnected from host) of the USB_SERIAL_JTAG
device during software reset.
When USB_SERIAL_JTAG is being used, whether to turn off the clock source during software reset and in
sleep modes is determined by RTC_CLOCK_BBPLL_POWER_ON_WITH_USB.
- When RTC_CLOCK_BBPLL_POWER_ON_WITH_USB is enabled, the clock will be kept, so that the
USB_SERIAL_JTAG will keep alive during software reset. The side-effect is the increasing of power
consumption during sleep modes, even though USB_SERIAL_JTAG will not work in sleep modes.
- When RTC_CLOCK_BBPLL_POWER_ON_WITH_USB is disabled, the clock will be turned off. USB_SERIAL_JTAG
will be inactive during software reset and in sleep modes. This saves some power consumption in
sleep modes.
When USB_SERIAL_JTAG is not being used, software will always turn off BBPLL regardless of
RTC_CLOCK_BBPLL_POWER_ON_WITH_USB is set or not.
endmenu
menu "Peripheral Control"