Setting Up Adc Ports

I switched from a 16F887a to 18F4610. I have everything running including a serial output controlling a dual pot.

My problem is always those darn adc ports. I need to set up and read analog on porta 0 -7. I get strange readings or nothing at all. I had it working fine on the 877A, but can't make the transition on the 4610.

A little sample code would be great. I admit I don't grasp the adcon settings, any simplified explanation would help, with examples. Maybe I can get my mind around these adcon settings.

Thanks,

Geezer

Hey Geezer -
One example that really helped me learn what to look for and how to read the data sheet for the A/D modules is HERE. I realize it's not the same micro you're working with, but Bruce does point out some very important steps on how to set up the A/D module. I haven't worked with the Pic 18x's yet, so I'm not even going to try to code anything without testing it. All I can say, is get to know the data sheet. Just by taking a quick look, it says

Quote:

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The module has five registers:
• A/D Result High Register (ADRESH)
• A/D Result Low Register (ADRESL)
• A/D Control Register 0 (ADCON0)
• A/D Control Register 1 (ADCON1)
• A/D Control Register 2 (ADCON2)

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ADCON0 controls

• turning on/off the ADC module
• starting the conversion
• indicating which channel to read

ADCON1

• voltage reference configurations
• AD port configuration bits

ADCON2 contains

• the result format
• acquistion time selection
• the conversion clock selection

ADRESH & ADRESL, of course hold the result from the A/D conversion. Chances are you'll have to do something with each one of these registers, depending on how you want to execute the A/D conversion. Sorry I don't have a cut & paste example for you, but maybe I've helped steer you in the right direction in figuring out the ADC module.http://www.picbasic.co.uk/forum/images/icons/icon12.gif

If I may put my 2 cents in here, I use A/D converters all the time. However, I don't "set up" anything except tell the device to turn all A/D ports to digital on boot. On 12F675 I use ANSEL = 0. On 16C72A, 16F72 and 16F818, I use ADCON1 = 7. Then, I simply use the ADCIN command and it works every time for a 0-255 reading. ADCIN 0, X will read ANA0 and put value into BYTE variable X. And if Anyone here knows why I shouldn't do it this way, please let me know. Thank you. - Peter

Thanks for the input guys. Peter, I am glad it is working out so easily for you.

I have it running now. I just ignored ADCON0 and set ADCON1 and 2. I think I know what i did to turn on 4 of the ports i need right now. We'll see how smart i am when i need to turn on the next 4.

Thanks again, I get a lot of help and good ideas from the forum.

The Geezer

Quote:

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Originally Posted by peterdeco1

if Anyone here knows why I shouldn't do it this way, please let me know. Thank you. - Peter

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More than one way to skin a cat. Sure the ADCIN command can be used and probably work just fine, and get him up and going quickly. I like using the ADC registers directly to understand what's all involved. Which from Geezer's post, I was under the impression he was after this as well. Other people also do this for speed and efficiency. Instead of telling someone to RTFM... I try to point them in the direction of examples and where to look in the manual to learn what they are after. Just a personal preference. Glad you got your project going Geezer... and hopefully you have a better understanding of the ADC module.