AD Negative Voltage reference

[flotulopex]

Voilà, this is how my circuit looks like:
<img src="http://www.picbasic.co.uk/forum/attachment.php?attachmentid=1820&stc=1&d=118301268 7">
Voltages I measure are:
1.- GPIO.5 = HPWM = 1,2V to 6,2V;
2.- GPIO.1 = AD = 1,2V to 5,1V.

To make it work (voltage control), I must connect R5. In the same time, voltage on GPIO.5 raises up from 0V to 1,2V.

Do I have to "protect" GPIO.5 pin against this 1,2V even if it is an Output?

If yes, how?

NB: is Vref limited to max 5V?