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Guest
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| Easy ADC question, pic16f684 |
 Posted: Wed Dec 16, 2009 6:39 pm |
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I'm just wondering if my PIC will automatically set my selected ADC pins as ANALOG. The device file says the following:
| Code: | // Constants used in SETUP_ADC_PORTS() are:
#define sAN0 1 //| A0
#define sAN1 2 //| A1
#define sAN2 4 //| A2
#define sAN3 8 //| A4
#define sAN4 16 //| C0
#define sAN5 32 //| C1
#define sAN6 64 //| C2
#define sAN7 128 //| C3
#define NO_ANALOGS 0 // None
#define ALL_ANALOG 255 // A0 A1 A2 A4 C0 C1 C2 C3 |
My code snippet is:
| Code: |
setup_adc(ADC_CLOCK_INTERNAL);
setup_adc_ports(sAN0 | sAN1 | sAN2 | sAN4 | sAN5 | sAN6 | VSS_VDD);
set_adc_channel(2);
delay_us(20);
adc=read_adc();
LPOT=128+adc; |
I want all of my chosen adc ports to be analog instead of digital. My question is whether or not my pic will automatically set them as analog inputs? If I add "ALL_ANALOG" to the "setup_adc" line, will it set my chosen pins as ANALOG, or every adc pin on the entire pic, whether or not I choose them? |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Wed Dec 16, 2009 7:27 pm |
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| Quote: | | I want all of my chosen adc ports to be analog instead of digital |
Yes, you are selecting pins to be configured as analog, when you
call that function.
| Quote: |
If I add "ALL_ANALOG" to the "setup_adc" line, will it set my chosen pins
as ANALOG, or every adc pin on the entire pic, whether or not I choose
them?
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All pins on the chip that can be analog will be made analog. |
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Guest
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| Posted: Wed Dec 16, 2009 7:33 pm |
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Thanks for the prompt response PCM, I didn't want to power my pic on with 3v going into each analog pin until I was sure, I've fried chips before because of this kind of thing.
Cheers! |
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Guest
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| Posted: Thu Dec 17, 2009 12:18 pm |
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I have another question reguarding the PIC16F684. I've programmed pins C3,C4,C5,A3,A4,A5 as blinking LED outputs, but I get strange results from A3 and A4. All of the other pins work perfectly. Pin A3 gives me a constant dim LED, and A4 gives me a constant BRIGHT LED. Pin A3 is also MCLR, but I've fused MCLR in my code.
Is there something I could be missing or forgetting to do? I can post the code if requested.
Thanks! |
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mkuang
Joined: 14 Dec 2007
Posts: 257
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| Posted: Thu Dec 17, 2009 1:12 pm |
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| Anonymous wrote: | I have another question reguarding the PIC16F684. I've programmed pins C3,C4,C5,A3,A4,A5 as blinking LED outputs, but I get strange results from A3 and A4. All of the other pins work perfectly. Pin A3 gives me a constant dim LED, and A4 gives me a constant BRIGHT LED. Pin A3 is also MCLR, but I've fused MCLR in my code.
Is there something I could be missing or forgetting to do? I can post the code if requested.
Thanks! |
I don't have the datasheet for the 684 downloaded but you have to make sure that A3 and A4 are not open-collector outputs in which case you need a pullup resistor to Vdd to make it work. |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Thu Dec 17, 2009 1:19 pm |
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Look in the Device Overview section of the 16F684 data sheet.
Look at this table:
| Quote: | | TABLE 1-1: PIC16F684 PINOUT DESCRIPTION |
It lists the restrictions on the pins.
http://www.microchip.com/wwwproducts/Devices.aspx?dDocName=en010214
Some pins may not be i/o. They may be listed as input only.
Other pins may have a dual use that is defined by a fuse setting.
For example, to use oscillator pins as i/o when using the internal
oscillator, you must use the INTRC_IO fuse instead of just INTRC. |
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