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TL
Joined: 15 Sep 2003
Posts: 75
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| 18F6720 ADC configuration problem |
 Posted: Thu Feb 03, 2005 5:21 am |
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Hi,
I am using the 18F6720 and PCWH. I would like to use the built-in ADC. However, I would like to use some pins as analog inputs and some for digital I/O’s.
Can I configure the following?
AN0 to AN2, and AN5 as analog inputs,
AN3, AN6 as digital outputs,
AN7 as digital input.
If so, what constants do I need to put into SETUP_ADC_PORTS() to make AN0 to AN2, and AN5 as analog inputs? Also, how can I configure the other AN ports as digital I/O' ports?
The following is an extract from the 18F6720.h file and it does not appear to have sufficient constants to configure the above analog inputs.
| Code: | ////////////////////////////////////////////////////////////////// ADC
// ADC Functions: SETUP_ADC(), SETUP_ADC_PORTS() (aka SETUP_PORT_A),
// SET_ADC_CHANNEL(), READ_ADC()
// Constants used in SETUP_ADC_PORTS() are:
#define NO_ANALOGS 0x0F // None
#define ALL_ANALOG 0x00 // A0 A1 A2 A3 A5 F0 F1 F2 F3 F4 F5 F6
#define ANALOG_AN0_TO_AN10 0x04 // A0 A1 A2 A3 A5 F0 F1 F2 F3 F4 F5
#define ANALOG_AN0_TO_AN9 0x05 // A0 A1 A2 A3 A5 F0 F1 F2 F3 F4
#define ANALOG_AN0_TO_AN8 0x06 // A0 A1 A2 A3 A5 F0 F1 F2 F3
#define ANALOG_AN0_TO_AN7 0x07 // A0 A1 A2 A3 A5 F0 F1 F2
#define ANALOG_AN0_TO_AN6 0x08 // A0 A1 A2 A3 A5 F0 F1
#define ANALOG_AN0_TO_AN5 0x09 // A0 A1 A2 A3 A5 F0
#define ANALOG_AN0_TO_AN4 0x0A // A0 A1 A2 A3 A5
#define ANALOG_AN0_TO_AN3 0x0B // A0 A1 A2 A3
#define ANALOG_AN0_TO_AN2 0x0C // A0 A1 A2
#define ANALOG_AN0_TO_AN1 0x0D // A0 A1
#define ANALOG_AN0 0x0E // A0
// The following may be OR'ed in with the above using |
#define VSS_VDD 0x00 // Range 0-Vdd
#define VREF_VREF 0x30 // Range VrefL-VrefH
#define VREF_VDD 0x20 // Range VrefL-Vdd
#define VSS_VREF 0x10 // Range 0-VrefH |
Please help. |
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rwyoung
Joined: 12 Nov 2003
Posts: 563
Location: Lawrence, KS USA
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| Posted: Thu Feb 03, 2005 8:52 am |
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Check the data sheet for the part. You will see the #def's match the table in the data sheet.
The short answer is you can't do exactly what you want to do. You can however set AN0 to AN5 as ADC inputs. and make AN7 a digital input and AN6 a digital output.
As to AN3, I'm a little fuzzy. I think it is OK for it to be a digital input if it is in the middle of an ADC channel range but I'm not so sure about it being a digital output.
One thing to do would be to write some code and single step it through the Microchip simulator in MPLAB and keep an eye on the port bits and their registers. Or just write some code and try it on your hardware...
_________________
Rob Young
The Screw-Up Fairy may just visit you but he has crashed on my couch for the last month! |
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TL
Joined: 15 Sep 2003
Posts: 75
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| Posted: Thu Feb 03, 2005 9:44 am |
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Many thanks for pointing me in the right direction. Yes, I’ve checked the datasheet and it will not do what I want. You can allow to have analog inputs and digital I/O’s (inputs and outputs) on port AN but they must be configured as per datasheet. Yes, I’ll try to group them and go from there.
Thanks
Tom |
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