How to make the serial port baud rate not change with temperature?

RE: How to make the serial port baud rate not change with temperature?

Einar Thorsrud — Tue, 12 Jun 2018 06:08:55 GMT

Hi,

Yes you are right. There was a typo in my initial answer, you should use nrf_drv_clock_hfclk_release() (the nrf_drv_clock_lfclk_release() is the corresponding function for releasing the LFCLK). I am sorry for the confusion. (I have updated the original answer to use the correct release function).

RE: How to make the serial port baud rate not change with temperature?

shark — Tue, 12 Jun 2018 01:37:03 GMT

Hi，

[release it when it is no longer needed by calling nrf_drv_clock_lfclk_release().]

This function is not wrong？

It should be nrf_drv_clock_hfclk_release()？

RE: How to make the serial port baud rate not change with temperature?

shark — Mon, 11 Jun 2018 14:45:34 GMT

When the crystal oscillator is not used, the current is 40uA, but the baud rate is unstable, and the baud rate is stable after using the crystal oscillator. When closing the serial port, call nrf_drv_clock_hfclk_release() to turn off the 80uA crystal current and call nrf_drv_clock_lfclk_release() to turn off the 200-800uA crystal current.
I hope that after turning off the crystal oscillator, the current will drop to 40uA. What should I do?

RE: How to make the serial port baud rate not change with temperature?

Einar Thorsrud — Mon, 11 Jun 2018 11:37:38 GMT

Hi,

The crystal oscillator has a higher current consumption than the RC, but you should see it come down after you have called nrf_drv_clock_hfclk_release(). The driver implements a counter, and will only disable the HFXO once the count comes back to 0. Have you made sure you call nrf_drv_clock_lfclk_release() and nrf_drv_clock_hfclk_release() the same amount of times?

RE: How to make the serial port baud rate not change with temperature?

shark — Mon, 11 Jun 2018 08:51:03 GMT

According to your method, the baud rate is stable. However, the current rises by about 40uA, and why the current rises. Turn off the external crystal using nrf_drv_clock_lfclk_release() and nrf_drv_clock_hfclk_release()will not work

RE: How to make the serial port baud rate not change with temperature?

Einar Thorsrud — Fri, 08 Jun 2018 06:45:55 GMT

Hi,

The HFRC oscillator is quite temperature sensitive, so the solution is to use the crystal oscillator (HFXC) instead when you need an accurate clock. The simplest is probably to use the clock driver. First initialize the driver usingnrf_drv_clock_init(). Then, you can start it by calling nrf_drv_clock_hfclk_request() and release it when it is no longer needed by calling nrf_drv_clock_hfclk_release().