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Hicham
Joined: 09 Feb 2010
Posts: 17
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| dual channel AD conversion in pic18F4331 |
 Posted: Thu Apr 08, 2010 2:42 pm |
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Hello,
I'm working with pic18F4331 and it has a multi-channel AD conversion.
Based on the datasheet, it has 4 places to save the value after conversion before putting them in the final registers (ADRESH,ADRESL),
in case of using dual or sequence conversion.
But I can't figure out how to get 2 values in the same time after a dual conversion in CCS.
Is there an example for this kind of conversion ?
Any examples code are much appreciated. |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Thu Apr 08, 2010 6:26 pm |
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The code shown below works with vs. 4.106. I don't have a 18F4331, so
I used an 18F4431, which is very similar. I set AN0 to 2.0 volts, and
AN1 to 3.0 volts. I get the following output on the terminal window:
| Quote: |
Ch0 = 411, Ch1 = 627
Ch0 = 411, Ch1 = 626
Ch0 = 411, Ch1 = 626
Ch0 = 411, Ch1 = 626
Ch0 = 411, Ch1 = 627
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This is basically correct, given an ADC output range from 0 to 1023
over a 0v to 5v range. 2.0v should be 409, and 3.0v should be 614.
My variable power supply can't put out exactly 3.00v. But close enough.
I don't guarantee that this program is exactly correct. I looked at the
data sheet and the .LST file, and keep playing with it until it worked and
until it looked like I was complying with the data sheet's instructions for
continuous dual sampling mode. But anyway, it's good enough to give
you a starting point. Remember, I don't want to do your project for you.
You must do any further work on it.
| Code: |
#include <18F4431.h>
#device adc=10
#fuses XT,NOWDT,PUT,BROWNOUT,NOLVP
#use delay(clock=4000000)
#use rs232(baud=9600, xmit=PIN_C6, rcv=PIN_C7, ERRORS)
#byte ADCON1 = 0xFC1
#byte ADRESL = 0xFC3
#byte ADRESH = 0xFC4
#byte ADCHS = 0xF99
#bit ADC_FIFOEN = ADCON1.4
#bit ADC_BFEMT = ADCON1.3
//======================================
void main(void)
{
int16 result0, result1;
// Select pins AN0 and AN1, in Groups A and B, respectively.
setup_adc_ports(sAN0 | SAN1);
// Tell ADC to read continuously from input Groups A and B.
setup_adc(ADC_CLOCK_DIV_2 | ADC_CONT_AB);
delay_us(10); // Wait 10us, per the 18F4431 data sheet.
// Tell the ADC to put the conversion results in the fifo.
ADC_FIFOEN = 1;
read_adc(ADC_START_ONLY); // Set the GO bit in ADCON0
while(1)
{
// Wait for the first A/D result to become available in the fifo.
// Then read it.
while(ADC_BFEMT);
result0 = make16(ADRESH, ADRESL);
// Wait for the 2nd A/D result to become available in the fifo.
// Then read it.
while(ADC_BFEMT);
result1 = make16(ADRESH, ADRESL);
printf("Ch0 = %lu, Ch1 = %lu \n\r", result0, result1);
delay_ms(1000);
}
} |
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Hicham
Joined: 09 Feb 2010
Posts: 17
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| Posted: Sun Apr 11, 2010 8:19 am |
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Thanks for this example, PCM programmer.
Now I understand how it works.
So, I have to create new bytes like "ADC_FIFOEN "
I thought they're already build-in CCS.
Anyway.. thanks for your help, and wait my new question soon. |
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