How do I do to measure the voltage on a certain pin?
Newbie is the welcome title for the person who has just joined with the Arduino Community. A Newbie could be a novice learner or a Learned One. It could be judged to some extent by looking at the content and presentation style of the post.
I assume that the OP has wanted to measure and display the Pin Logic of a specific digital pin - that means converting the DUE into a DVM. The following steps may be exercised:
1. Assume DPin-8 and configure it as output.
2. Connect DPin-8 with A0-pin with jumper.
3. Initialize analog channel-0 as needed.
4. Write LL at DPin-8.
5. Use a hand-held DVM (as a secondary calibrator) and measure logic level of DPin-8.
6. Acquire and record ADC value of Ch-0.
7. Record Step-5 and Step-6 as: A(ADCL, 0) or A (VDC1, 0).
8. Write LH at DPin-8.
9. Use a hand-held DVM (as a secondary calibrator) and measure logic level of DPin-8.
10. Acquire and record ADC value of Ch-0.
11. Record Step-9 and Step-10 as: B(ADCH, 3.3) or B(VDC2, 3.3).
12. Derive equation for unknown point C(ADC, V) from the known points: A and B.
13. Show the decimal value of V onto LCD Monitor or Serial Monitor or 7-segment Monitor.
The DUE-based DVM is here!