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

[shark]

How to select nrf528332 UART clock source, how to make the serial port baud rate not change with temperature?When the baud rate is 9,600, the baud rate varies greatly with the temperature.Baud rate when - 25 ℃ maximum deviation to 3.5%, when to 55 ℃ baud rate deviation of 2.1%.

[Einar Thorsrud]

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().

[shark]

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

[Einar Thorsrud]

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?

[shark]

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?