Setting up PLL
Posted: Sun Apr 29, 2018 9:12 am
Hi,
I cannot find anywhere how to set up correctly PLL. https://github.com/espressif/esp-idf/bl ... #L274-L375 there is some basic setup but to be honest I does not seem to me to be the best idea to support just few XTAL frequencies and do not leave any docs saying how to do it for any other XTAL. Is there any very specific reason why there are only these - 40 MHz, 26 MHz, 24 MHz - frequencies supported?
I also wonder why there there are just few CPU frequencies (XTAL, 240 MHz, 160 MHz, 80 MHz, 2 MHz) while APB_CTRL_PRE_DIV_CNT can give us many frequencies within range 40 MHz - 2 MHz. I do understand that in most scenarios will be used one of PLL frequencies but still.. why not to support a general scenario instead of few cases?
I am trying to build a custom ESP32 SDK more focused to bare metal development (without FreeRTOS).
Also please see viewtopic.php?f=2&t=2772&p=14747&hilit=pll#p14725
I cannot find anywhere how to set up correctly PLL. https://github.com/espressif/esp-idf/bl ... #L274-L375 there is some basic setup but to be honest I does not seem to me to be the best idea to support just few XTAL frequencies and do not leave any docs saying how to do it for any other XTAL. Is there any very specific reason why there are only these - 40 MHz, 26 MHz, 24 MHz - frequencies supported?
I also wonder why there there are just few CPU frequencies (XTAL, 240 MHz, 160 MHz, 80 MHz, 2 MHz) while APB_CTRL_PRE_DIV_CNT can give us many frequencies within range 40 MHz - 2 MHz. I do understand that in most scenarios will be used one of PLL frequencies but still.. why not to support a general scenario instead of few cases?
I am trying to build a custom ESP32 SDK more focused to bare metal development (without FreeRTOS).
Also please see viewtopic.php?f=2&t=2772&p=14747&hilit=pll#p14725