Port RA5 on PIC16F876A

[ccola]

OK first of I'm still getting my feet wet with pic programming so this is probably a simple answer is just has me stuck.

Is there something special about PortA.5 that I'm missing?

I'm using PBP, on a PIC16F876A, below is a small part (abbreviated) of the code, I am pulling portA pins low with a switch, and they should then light up the LEDs on portB in theory PortA.2 is measuring the value of a pot to adjust the amount of time the LED is on. Everything works except for PortA.5 it is just dead no matter what state PortA.5 is in it has no effect on the PortB.5 LED...

Y var Word

Define ADC_BITS 8
Define ADC_CLOCK 3
Define ADC_SAMPLEUS 50

ADCON1 = 7

PortA = %11111111
TrisA = %11111111
PortB = %00000000
TrisB = %00000000

main:

adcin 2, Y
Y = Y * 10

If PortA.0 = 0 Then
PortB.0 = 1
Pause Y
PortB.0 =0    
Endif

'This part of the code below doesn't work?

If PortA.5 = 0 Then
PortB.5 = 1
Pause Y
PortB.5 = 0    
Endif

Goto main

 

[Nigel Goodwin]

By default RA5 is an analogue input (along with ALL other analogue inputs), you don't show any code configuring the analogue pins - so I can only assume it's still set as an analogue input?.

 

[ccola]

Like I said I'm just getting my feet wet so yes, nothing is configured I guess and that is probably my problem?

It just puzzles me that portA 0, 1, 2, 3, 4 all work as is in the program but 5 just won't function....

 

[Nigel Goodwin]

Like I said I'm just getting my feet wet so yes, nothing is configured I guess and that is probably my problem?

It just puzzles me that portA 0, 1, 2, 3, 4 all work as is in the program but 5 just won't function....

Check the datasheet for the 16F876, or try my analogue tutorial at the URL listed below (which is probably simpler?), there are restrictions as to which pins can be analogue, you can't simply have individual ones at random as analogue - they have to be in a set pattern.

You need to check with your compiler about how to configure the analogue inputs, my assembler tutorial probably won't help you with that!.

BTW, there are only 5 analogue pins on PortA, and RA4 isn't one of them!, that's an open collector output pin (or a digital input pin), that often gives problems!.

 

[martinH]

OK first of I'm still getting my feet wet with pic programming so this is probably a simple answer is just has me stuck.

Is there something special about PortA.5 that I'm missing?

I'm using PBP, on a PIC16F876A, below is a small part (abbreviated) of the code, I am pulling portA pins low with a switch, and they should then light up the LEDs on portB in theory PortA.2 is measuring the value of a pot to adjust the amount of time the LED is on. Everything works except for PortA.5 it is just dead no matter what state PortA.5 is in it has no effect on the PortB.5 LED...

Y var Word

Define ADC_BITS 8
Define ADC_CLOCK 3
Define ADC_SAMPLEUS 50

ADCON1 = 7        

PortA = %11111111
TrisA = %11111111
PortB = %00000000
TrisB = %00000000

main:

adcin 2, Y
Y = Y * 10

If PortA.0 = 0 Then
PortB.0 = 1
Pause Y
PortB.0 =0    
Endif

'This part of the code below doesn't work?

If PortA.5 = 0 Then
PortB.5 = 1
Pause Y
PortB.5 = 0    
Endif

Goto main

Adcon1=7 sets all porta pins to digital mode
I suggest you move your pot to AN0 and use adcon1=14 or adcon1=%1110
this sets AN0 to analog and AN1-7 as digital



Mart