Long timer interrupt periods

[Indois]

Hello,

I would like to have timer interrupts every 10 minutes for temperature readings. Also, I would like to have opportunity to change this period in the code. How could such long period be implemented? Are there any examples? I am using STM32L011F4 MCU and STM32CubeIDE environment.

Thank you.

[waclawek.jan]

Set the timer's prescaler and ARR so that resulting time is 10 minutes.

If it's not possible with chosen timer, set it to a suitable long period, and in the interrupt count up until the required time elapsed.

Alternatively, chain timers using master-slave connection, use the slave in external clock mode, and set both timers' PSC and ARR to match the required period.

JW

[Indois]

STM32CubeMX clock configuration settings (MCU works at maximum 32 MHz):

 

Generated Timer init function:

 

The maximum period I can enter is 65 536 ms (2^16) which is 65.536 seconds. If I enter for example 70 000 then timer interrupts every 5 seconds.

How could I set period to 10 minutes (600 000 ms)?

[waclawek.jan]

Set it to 1 minute (60 seconds), and in the interrupt service routine (ISR) count to 10.

JW

[Indois]

But if I use counting, it will act like delay which results in blocking the program. In such case period could not be changed during operation.

[Ons KOOLI]

Hi @Indois​ ,

Please refer to the AN3964. This application note describes a method of implementing a simple application for temperature measurement using the STM32L-DISCOVERY and 32L152CDISCOVERY boards. You can start from here and port it to your preferred board. When powered up, the temperature sensor application example first displays a welcome message before immediately displaying the current temperature in degrees Celsius with a 2-second refresh rate.

Best Regards,

Ons.

[Indois]

I am reading temperature from external sensor and would like to have long periods (like 10 minutes) between readings.

[Indois]

Maybe there are other methods to code interrupts for at least every 10 minutes (without timers)? I would like to have opportunity to change period during operation, so delay function could not be used in this case (it blocks the program operation).

[waclawek.jan]

> But if I use counting, it will act like delay which results in blocking the program.

No.

Simply setup up the timer for the 1 minute period, enable it, enable interrupt, and set a global variable to 10. In the ISR, decrement that global variable, and once it reaches 0, you do your action (temperature measurement). Counting happens only once in a minute in the ISR, the rest of program runs as usually.

JW

[Tesla DeLorean]

For long duration presumably you could use the RTC Alarm?