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PWM Generation using Flex Timer Module(FTM)

Question asked by Karthick Sivakumar on Jul 11, 2016
Latest reply on Jul 25, 2016 by Robin_Shen

Hi All,


We are using K70 processor in one of our board and controlling 4 stepper motor using allegro driver IC.

We are generating PWM pulses using FTM module and we found that while we use FTM and generate say 16 pulses with defined width we are getting one extra pulse occasionally. This behavior we found in both low true pulse and high true pulse configuration.


Also we have another issue when we configure as high true pulse instead of clear output on match it behaves like low true pulse(its sets output on match). Please find below the snap shot.




When we tried to configure it as GPIO and toggle we are not facing any of the above issue, ie we are not getting extra pulse or behaves as intended.


To give the hardware background we are using K70 Processor in one board (control board) and Allegro A4989 drive IC in another board (Motor Driver board).

We have a non inverting buffer 74AC541MTC in control board (in between K70 processor and Allegro Driver).

We have directly connected K70 PWM pin output to buffer (with no pull up/pull resistor at buffer input) and then buffer output connects to driver IC.

Please tell us why we are facing this issue only when we configure the IO pin as FTM and generate PWM but not when we configure as GPIO and toggle.


Thanks for your time.