Measuring LPO_CLK frequency for RTWDOG?

[p_shep]

I've seen mention that the internal 32KHz RC oscillator (Low-Power Oscillator) is pretty loose and can be anywhere from 10KHz to 40KHz.

Is there any way to measure this, so when specifying a timeout for the WDOG, we can get it somewhere near? e.g. Using another timer in some way?

[imxrtuser]

Hello p_shep,
where did you find the 10kHz to 40kHz range?
In the document i.MX RT1050 Crossover Processors Data Sheet for Industrial Products, Rev. 1.3, 03/2019 I found two different specifications:

- chapter 4.1.4 External clock sources:
On-chip 40 kHz ring oscillator with approximately +/-50% tolerance

- chapter 4.2.4.2 OSC32K:
The frequency range of this block is
approximately 10–45 kHz. It highly depends on the process, voltage, and temperature.

Kind regards,
Stefan

[p_shep]

Oh, random googling. So I probably read one of those you quote there and made the assumption.

I can say that setting a 20s timeout will trigger a watchdog at about 16 seconds. 

[EdwinHz · Accepted solution]

Hi @p_shep,

I'm afraid there isn't a viable way of achieving this, this is why we always recommend using an external 32KHz RC Oscillator and keep the use of the internal oscillator strictly as a backup. Sorry for the inconvenience this may cause.

BR,

Edwin.