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jspencer
Joined: 22 Dec 2003
Posts: 57
Location: Boise, ID USA
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| ADC on 16F689 channel 13 |
 Posted: Fri Oct 20, 2006 4:34 pm |
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Just a quick question. I need to use channel 13 on the 16F689 as a comparative reference. What do I use for setting up the port when calling:
| Code: | | setup_adc_ports(sAN0 | VSS_VDD); |
sAN13 is not a valid option in the 16F689.h file. To make it a valid option I can define it, but what value does it need to be assigned to make it work correctly?
| Code: | #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 sAN8 0x10000 //| C6
#define sAN9 0x20000 //| C7
#define sAN10 0x40000 //| B4
#define sAN11 0x80000 //| B5
// My definitions for channels 12 and 13
#define sAN12 0x100000 //| CVref
#define sAN13 0x200000 //| VP6
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Would this be correct, or am I totally wrong in my thinking? Or since they are not ports, do I even need to do a setup_adc_ports() call for channels 12 and 13?
Thanks!
jspencer |
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Ttelmah
Guest
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| Posted: Sat Oct 21, 2006 2:19 am |
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The 689, does not support 13 channels on the ADC.
Look at table 4, in the data sheet.
It supports analog channels AN0 to AN11, which is what the existing setup already gives you. Pin 13 on the chip, connects to AN10, which may be what you are referring to. Vref for the ADC, can only use the supply rail, or RA1.
Best Wishes |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Sat Oct 21, 2006 10:43 pm |
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Do you want to read the VP6 voltage with the A/D ?
To do that, you basically need to enable VP6 and then
select channel 13. I don't have a 16F689 to test, but
I've read the data sheet and I think the following program
should work:
| Code: |
#include <16F689.h>
#device adc=10
#fuses XT, NOWDT, NOPROTECT, PUT, BROWNOUT
#use delay(clock=4000000)
#use rs232(baud=9600, xmit=PIN_B7, rcv=PIN_B5, ERRORS)
#byte VRCON = 0x118
#bit VP6EN = VRCON.4
//=====================================
void main()
{
int16 result;
VP6EN = 1; // Enable VP6 voltage (0.6v)
delay_us(100); // Wait for required settling time
setup_adc(ADC_CLOCK_DIV_16); // Use /16 with a 4 MHz xtal
set_adc_channel(13); // Select channel for VP6
delay_us(20);
result = read_adc();
// The A/D value for VP6 should be approximately 123.
// (With the PIC's Vdd at +5.0 volts, and a 10-bit A/D).
printf("result = %lu\n\r", result);
while(1);
} |
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jspencer
Joined: 22 Dec 2003
Posts: 57
Location: Boise, ID USA
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| Posted: Mon Oct 23, 2006 9:30 am |
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PCM that is correct. Since I do not have a constant Voltage supply (3V coin cell) we are going to use the ratio of the VP6 to scale the ADC channels readings appropiately. After doing a little more reading, what you posted is what I came up with. I will give it a shot today and see how it works.
Thanks!
jspencer |
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