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KE02 GPIO Strange Behavior

Question asked by Jorge d'Avila on Sep 22, 2017
Latest reply on Sep 23, 2017 by Mark Butcher

Hello!

I'm fighting a strange behavior in what should be a very simple situation:

  • MCU MKE02Z16VLD2;
  • I need to use 2 pins (PTB1, PTB2) alternately as Input and Output;
  • When using them as Inputs, my external drive is very low current, so I rely on the MCU having a very low leakage current. Datasheet say this current is typically 0.1uA, max 1uA;
  • When testing the circuit, the external drive was not capable of driving the MCU pins. Further search showed the port leaking a much higher current - in the order of 100uA;
  • For a test circuit, I connected each pin to a pair of resistors, 33k, to GND and VDD, making in effect a load near 100uA when driven High or Low;

 I compiled and ran this test code:

for (;;)
   {
   FGPIO_PCOR_REG (portIO) = maskIO2 | maskIO3;       // IO LO
   FGPIO_PDDR_REG (portIO) |= (maskIO2 | maskIO3);    // IO Output  0.008
   FGPIO_PDDR_REG (portIO) &= ~(maskIO2 | maskIO3);   // IO Input   0.187
   FGPIO_PSOR_REG (portIO) = maskIO2 | maskIO3;       // IO HI
   FGPIO_PDDR_REG (portIO) |= (maskIO2 | maskIO3);    // IO Output  3.321
   FGPIO_PDDR_REG (portIO) &= ~(maskIO2 | maskIO3);   // IO Input   2.736
   }

Single stepping through this code, I measured, after each line execution, the voltages shown at the right:

  • After driving the pin Low and reverting it to Input, it remains at a very low voltage;
  • After driving the pin High and reverting it to Input, it remains at a very high voltage;
  • A short circuit to the opposite rail, by means of a current meter, show the current to be around 100uA, also.

 

I must say I'm stuck! No idea why this is happening. I would appreciate anyone pointing out where am I busting it!

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