8.1 Set Up VDDIO2 Failure Detection

Todo:
  • Edit mvio_init() so it enables the VDDIO2 status change interrupt
  • Edit ISR(MVIO_MVIO_vect) to handle the VDDIO2 status change interrupt
  • Plot the measured VDDIO2 values in MPLAB® Data Visualizer
Warning: This assignment assumes the hardware setup steps described in Assignment 6 have been completed. If they have not been completed, the step-by-step instructions can be found in MVIO Hardware Setup.
Info: The DAC, ADC and OPAMP peripheral are all configured in the same way as it was done for assignment 6. The description of the setup can be found in Measuring VDDIO2 Using the ADC.
  1. Enable the VDDIO2 status change interrupt by editing mvio_init() to include:
     MVIO.INTCTRL = MVIO_VDDIO2IE_bm;
  2. Handle the interrupt by clearing the interrupt flag and toggling LED0 by adding the following to ISR(MVIO_MVIO_vect):
    MVIO.INTFLAGS = MVIO_VDDIO2IF_bm;
LED0_toggle();
  3. Understand how the VDDIO2 fault is injected when SW0 is pressed by lowering the op amp output by looking at the ISR(PORTB_PORT_vect) found in gpio.c.
    Info: When VDDIO2 goes below the acceptable range, the VDDIO2 Status bit goes low, triggering the VDDIO2 status change interrupt. When VDDIO2 is below the acceptable range, all the pins on PORTC are tri-stated. When VDDIO2 goes back up again, the values from the PORTC registers are loaded again.
  4. Verify that the solution/project builds by selecting the Build → Build Solution from the top menu bare in Atmel Studio or by pressing the F7 key.
  5. Flash the device by selecting the Debug → Start without debugging from the top menu bar in Atmel Studio or by pressing the Ctrl+Alt+F5 keys.
  6. Plot the measured ADC reading and the status of LED0 in MPLAB® Data Visualizer by loading the workspace Assignment7.json.
    Info: LED0 is active low, so the plot in MPLAB® Data Visualizer will show ‘0’ when the led is lighting and ‘1’ when it is off.
Result: The ADC measurements and SW0 states are plotted in MPLAB® Data Visualizer, as shown in Figure   1. It can be seen that as soon as SW0 is pressed and VDDIO2 goes below the acceptable value, the VDDIO2 status change interrupt triggers, and the LED0 line goes high. When SW0 is pressed again and VDDIO2 goes back into the acceptable range, the LED0 goes back low. The blue line is the VDDIO2 reading, while the green line is LED0.
Figure 8-1. Assignment 6: Result