[SOLVED] how to enable multiply output pins in pic12f675

[Yogeshwari]

When i use multiple output pins in pic12f675, voltage in second port is divided. Can anyone help me to resolve this problem.

 

[betwixt]

Please show your schematic. It sounds as though you are either overloading the PIC outputs, have insufficient supply current available or by adding the second port you are forcing the watchdog timer to cyclically reset the PIC.

Brian.

 

[Yogeshwari]

Thank you for the reply.
Watchdog timer was disabled and i didn't connect any load to check. I gave 3.1V input and when i measured voltage across AN0 i was getting 2.2V and 0.841V across AN1. I feel the input voltage is getting divided. Can u please tel me what might be the proble.
And can u please clarify whether i can use pic12f675 for 10 bit ADC with 4 output channels.

 

[betwixt]

Your question is not clear.

You mention output pins in the title but then say you are applying voltages at the ADC inputs. ADC is for measuring voltages at the analog inputs, it will not produce any voltages out of the PIC, you need a DAC to do that. The 12F675 only has ADC so it can only measure voltages you provide at it's 4 inputs.

If you are measuring the voltage on AN0 correctly but AN1 is also showing a small reading, it can be two things:
1. The impedance driving AN1 is too high or you have nothing driving it at all. Microchip recommend < 5K drive impedance.
2. When you change input channels (CHS0:CHS1 bits) you are not allowing enough time for the internal sample and hold amplifier to adapt to the new voltage.

Brian.

 

[Okada]

ADC registers are not configured properly.

- - - Updated - - -

There are 4 ADC Channels in PIC12F675. They are input pins for ADC and not output pins. You can't output analog voltages. You can input analog voltges into these pins and they will be converted to digital value. They are 10 bit ADC channels and hence 5V adc input will give you 1023 raw adc value (0 - 1023 = 1024 steps).