How to wake up with FXTH8711 Timer?

[aliyolcu]

Hi,

In my project, I want the FXTH8711 sensor to wake up and measure in a time-dependent manner, and to send data via SPI if it is below the threshold value I set during the measurement.

There is no problem in sending the values via SPI and measuring the Temperature and Pressure values from these processes, but I could not do the time-dependent wake-up event. Can you share a sample code for this? I read the RUN Mode, STOP4 Mode, STOP1 Mode states on page 92 of FXTH's datasheet but nothing came to mind.

Thanks,

Ali

[TomasVaverka · Accepted solution]

Hi Ali,

The application can use the Periodic Wake Up (PWU) block. This block can be configured to generate a periodic wakeup or a periodic reset. It can never be disabled. The Starter Package for FXTH87/87E that can be downloaded from here includes demo projects named “FXTH87_E_xx_Periodic_RF_Tx" which use the PWU block to wakeup the device periodically and trigger sensor measurements.

The PWU block is clocked by the LFO, which drifts with temperature. The frequency range is indicated in the datasheet. The functions provided by NXP include the functions TPMS_LFOCAL_xxx which allow to configure the PWU wakeup according to the actual LFO frequency, in order for the wakeup period to remain the same whatever the temperature. In the Documentation folder of the Starter Package mentioned above there is a User Guide explaining how to use these functions (TPMS_New_TPMS_LFOCAL_Lib_UserGuide_rev2).

Best regards,

Tomas