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USB CDC link lost on MK22FN and PC

Question asked by shuichiy on Oct 19, 2018
Latest reply on Oct 19, 2018 by Mark Butcher

Hi all,

 

I have a project based on USB CDC Vcom Lite sample.

The project is developed on KSDK2.4.1 and the mcu is MK22FN128VLH10.

 

In addition to CDC, 2ch ADCs  and a PIT timer work together.

Snippet is as follows:

 

void PIT0_IRQHandler(void)
{
  if  (PIT_GetStatusFlags(PIT, kPIT_Chnl_0) != 0)  {
    PIT_StopTimer(PIT, kPIT_Chnl_0);
    PIT_ClearStatusFlags(PIT, kPIT_Chnl_0, PIT_TFLG_TIF_MASK);
     ADC16_SetChannelConfig(ADC0, 0, &adc16ChannelConfigStruct0);
     ADC16_SetChannelConfig(ADC1, 0, &adc16ChannelConfigStruct1);
  }
}
void ADC0_IRQHandler(void)
{
  ADCData0 = ADC16_GetChannelConversionValue(ADC0, 0);     
}
void ADC1_IRQHandler(void)
{
  ADCData1 = ADC16_GetChannelConversionValue(ADC1, 0);     
  PIT_StartTimer(PIT, kPIT_Chnl_0);
}

 

Symptoms:

The period of PIT timer is 20us or more, it works fine.

The period is less than 20us, Windows  loses the link of USB.

 

II think PIT or ADC interrupts effect on something USB features.

Does someone know the restriction of USB interface or workaround of this ?

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