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Using FTM3 with Internal Oscillator (KV31f512)

Question asked by Peter Hedlund on Apr 10, 2019
Latest reply on Apr 10, 2019 by Peter Hedlund

I am using the internal oscillator with the KV31F512 Processor.

Our application is a Brushless DC motor controller. (phase u Hi, low, phase v hi, low and phase w hi and low)

I was given a board design that already existed but was never tested.

All 3 of the lo phases are just on and off, All 3 of the hi phases are gated PWM's 

Phase U is PortA13 FTM1-CH1

Phase V is PortE25 FTM0-CH1

Phase W is PortE6  FTM3-CH1


Using the FRDM-kv31f and subbing PortC2 for PortE25 The software runs and i get the expected signals.


Our Target board however does not an external crystal and we must use the internal oscillator.

I have an UART2 working at 115200 without issue.

I have a timer running to control the start/stop of the 3 phases.


PhaseW does not work.

Further testing has found that if i comment out code for Phase U and Phase V, and only have Phase W enabled, I get pulses on Phase U.


Since this worked on the FRDM-KV31F board and not our target I am wondering if there is some interaction i am unaware of when using the internal oscillator.


If you need to I can send code snippets to show what i am doing.


I know the preferred method is to use ONE FTM for a motor but the layout was already done.


Thanks in advance.


Peter Hedlund