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How to use combined FTM instances

Question asked by Frank Schuetz on Feb 22, 2016
Latest reply on Sep 20, 2017 by Hedi Hadhri

Hello,

 

I use the TWR-K65F180M with KSDK 1.3.0 and KDS 3.0.0.

 

I have developed successfully a software driver that we can capture a run length of a digital signal. There is a FTM counter for counting the run length and there is a set up of 2 eDMA channels to capture the counting values. There are 2 buffers, one for rising edges and one for falling edges. Each buffer is written by a eDMA channel. If the buffer is complete a DMA ISR is occurred and the counting values can be processed further.

So far so good.

 

Now, there is a new requirement:

If a high phase of this run length signal is greater than a fix specified value then a digital output must be switch on immediately.

The CPU may not be occurred!

 

My question is now:

How can I implement this feature?

 

My idea #1:

It is possible to configure the eDMA channel in this way that the FTM2 counter will be reset on each minor loop? So I could configure maximum counter value of FTM2 counter to the fixed value. And if the counter is overflowed then an interrupt will be generated to set a digital output.

 

My idea #2 (maybe the better way):

A new instance or FTM is set up (i.e. FTM3) to generate the digital output signal. The counter value of this instance must be reset every time by a positive edge of the captured run length signal and specified fix value will be write into a specified FTM3 register. If the counter value is grater than the fix value then the FTM3 set the output to high. I don't know if it is possible in this way.

 

 

Do you have a better idea?

If you have a solution, please can you give me an example?

 

Thanks in advance!

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