A/d 16f88

[flotulopex]

Hi Steve,

Don't use a VAR to define the A/D channel. Use the channel's number instead:

ADCIN 5, bat

You can test your project with your code I trimmed to minimum:

INCLUDE "modedefs.bas"

Define LCD_DREG PORTA
Define LCD_DBIT 0
Define LCD_RSREG PORTA
Define LCD_RSBIT 6
Define LCD_EREG PORTA
Define LCD_EBIT 4
Define LCD_BITS 4

bat  var byte

OSCCON = %01100000
ANSEL  = %00100000

Bat_Volts:
   ADCIN 5, bat
   LCDOut $FE, 1, "Battery = ",DEC bat, "V"
   PAUSE 2000
   goto Bat_Volts:
end

BTW, PORTB.6 is ADC Channel 5
<img src="http://www.picbasic.co.uk/forum/attachment.php?attachmentid=3431&stc=1&d=124367750 7">

[tenaja]

Don't use a VAR to define the A/D channel. Use the channel's number instead:

ADCIN 5, bat

I strongly disagree with this. First, in this particular example, he's using Ai as a constant, not a changing variable. That allows you to change PICs (or PIC pins), and just change the setup constant, without searching for all of the references to the pin.

Second, there is nothing wrong with using a variable variable to read adcin.

What you did do wrong, however, is you referenced the AN# with a PORT#. You don't do that. You should only use the ANx number; in this case, assuming your comments are your target, 6, NOT Portb.7.

Correct:
adcin 6, bat
NOT Correct:
adcin portb.7, bat

Correct:
Ai var 6 'Notice we use "x" of ANx.
adcin Ai, bat

NOT Correct:
Ai var portb.7 'Do NOT use the Port pin the ANx is on.
adcin Ai, bat

[flotulopex]

hum...

Correct:
Ai var 6 'Notice we use "x" of ANx.
adcin Ai, bat

Doesn't work for me.

It will work like this:

Ai CON 6
ADCIN Ai, bat

... or:

Ai VAR BYTE
Ai = 6
ADCIN Ai, bat

Or do I miss something?

NB: addressing PORTs via variable/constant is a best practice not a must.

[tenaja]

Yes, you are right... in my haste I edited it incorrectly.

I believe using a number is the worst way to do it, because it has no description behind it.

A constant is just as tight as far as compiling goes, and a variable is the way to go if you need to change which port you are reading within the loop. Both of these have the advantage that you can change all of your constants up at their definitions on the top, and you can change them easily when you move things around, like to a different PIC or pin. Also, compare these two, which do the exact same thing:

adcin 6
vs.
adcin BatteryVoltagePin

Which is easier to understand? Obviously the second. And if you use three a/d ports, with the constants all defined in a row and then you need to move things, it's one edit at the top for each... no searching and replacing multiple lines.

[Steves]

Thanks to you both. Roger your code works fine. I'll read thru your comments and revisit the data sheet for a better grasp of it all.