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How to measure MSI Clock in STM32 NUCLEO-L433RC-P board using Timer

SDasa.1
Associate II

I am working on Ultra low power application MSI clock as 800KHZ. 

My goal is to measure the MSI Clock, when the temperature changes in the System.

If I try to configure “Tl1 remap capabilities for TIM16�? as TIM16 Channel 1 is connected to LSI, then I can to read the LSI Clock correctly. But, I am interested in MSI Clock measurement. Could you please some one let me know how to Calculate MSI Clock using Timer 16.

2 REPLIES 2
TDK
Guru

Measuring MSI while also using MSI as the clock source will not yield a useful result. What are you trying to get out of that measurement?

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SDasa.1
Associate II

0693W00000D2f5wQAB.pngMy Goal is to measure deviation of MSI Clock , when the temperature changes.

From AN4736, Section 2 : Internal RC oscillator calibration

The frequency of the internal RC oscillators may vary from one device to another due to manufacturing process variations. For this reason, the MSI and the HSI16 RC oscillators are factory-calibrated by ST to have an accuracy of [min -0.75 %, max 0.5 %] at TA = 30 °C. After reset, the factory calibration value is automatically loaded in the internal calibration bits. The frequency of the internal RC oscillators can be fine-tuned to achieve better accuracy with wider temperature and supply voltage ranges. The trimming bits are used for this purpose.

In our application,

we are using MSI RC Clock = 800 KHZ, which results SYS CLK = 0.8 MHZ. In addition to this, we are using LP TIM (Low power Timer) configured with Standalone: counts external clock events as waveform generation using external clock (13.56MHZ) . This is only clock source we have reference setup. I would like to measure MSI Clock frequency with temperature change from 20C to 70C with TIM16 without changing H/w pin options.

My objectives :

1.      Would like to validate the MSI Clock frequency with temperature change from 20C to 70 C with TIM16 below option: