Hello everybody i would like to know were de vref 5V is connected on a pic 16F628, pin 1 (VREF)
thank you

 

Hi Math.
Check these d/s clips.
E

 

It come ftom the voltage refference module. See section 10 (Page 59) of the PIC16F628 datasheet.
Les.

 

OK thank you eric gibbs and les jones

 

so pin 1 RA2 where do i need to connect it?

 

so pin 1 RA2 where do i need to connect it?

hi math,
How are you planning to use the RA2 pin , ..... VREF,, ADC,, or I/O.. ?
E

 

What do you need it configured as?
If using as a GP I/O port then just configure it as such?!

 

HI eric gibbs, maxhead rooms i want to use vref 5v like reference to create a variable pwm with external potentiometer

 

So you cannot use the regulated IC supply ?
What are you operating at?

 

HI eric gibbs, maxhead rooms i want to use vref 5v like reference to create a variable pwm with external potentiometer

Hi math,
For that application you would set the RA2 pin as a VREF output, driving a high input impedance OPA.

The Vout of the OPA would drive a potentiometer, whose wiper could be used to control the ratio of a PWM generator.

Write the PIC Code for RA2/VCON to suit the range of voltage you require as an RA2 output voltage, Bits 5, 3,2,1,0

E

 

From what you say in post #8 you seem to think the vref on the PIC16F628 is generated frim an internal precision voltage reference module s it is in some other PICs. It is just derived from the 5 volt power supply via a ladder network as shown on page 59 of the data sheet. (It is a bit like a DAC without the output buffering.) The PIC16F628 does not have an ADC so you can't use it to feed the voltage from the slider on the potentiometer into the PIC to control the PWM duty cycle. To do what you seem to want to do you will need a different PIC. I have done something similar to what I think you may be trying to do using a PIC16F876. This was for a closed loop motor speed controller driving the X axis of a milling machine. You would get better help if you provided more details of your project.

Les.

 

lesjones; thats write! i will try with another pic!
eric gibbs: ok thank you