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Eddy71ua
Joined: 23 Sep 2009
Posts: 55
Location: Ukraine
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| [Solved] ADC PIC16F1823 ..half-work |
 Posted: Wed Jul 18, 2018 8:33 am |
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An incomprehensible problem arose: the reading of the channel AN3 gives only zero continuously. AN6 reads normally.
It seems to me that the channel does not turn on
| Code: |
#include <16F1823.h>
#device adc=10
#fuses INTRC_IO,NOWDT,NOPUT,PROTECT,NOIESO,NOFCMEN,WRT,NOSTVREN,NOLVP,NOMCLR,NODEBUG,BORV25
#use delay(clock=8000000)
#use fast_io(a)
#use fast_io(c)
#zero_ram
#use rs232(baud=9600,parity=N,xmit=PIN_C3,bits=8)
//----------------------------------------------//
void main(){
int16 Tmp16;
setup_oscillator(OSC_8MHZ);
setup_wdt(WDT_OFF);
setup_timer_0(RTCC_INTERNAL|RTCC_DIV_4);
setup_timer_1(T1_DISABLED);
setup_timer_2(T2_DISABLED,0,1);
setup_comparator(NC_NC_NC_NC);
set_tris_a(0b011110);
set_tris_c(0b000100);
port_a_pullups(0b110);
port_c_pullups(false);
setup_adc_ports(sAN3|sAN6|VSS_VDD);
setup_adc(ADC_CLOCK_DIV_8);
setup_vref(VREF_ON|VREF_ADC_1v024);
setup_adc_reference(VSS_VDD);
for(;;){
set_adc_channel(sAN3);
delay_us(200);
Tmp16 = read_adc();
printf("nA = %lu \r",Tmp16);
set_adc_channel(sAN6);
delay_us(200);
Tmp16 = read_adc();
printf("nB = %lu \r",Tmp16);
delay_ms(1000);
}
}
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PCWHD v5.078
Last edited by Eddy71ua on Wed Jul 18, 2018 11:27 am; edited 1 time in total |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Re: ADC PIC16F1823 ..half-work |
| Posted: Wed Jul 18, 2018 9:05 am |
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| Eddy71ua wrote: |
set_adc_channel(sAN3);
delay_us(200);
Tmp16 = read_adc();
printf("nA = %lu \r",Tmp16);
set_adc_channel(sAN6);
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That's not the correct way to set the A/D channel.
You must use the actual channel number, such as 3 or 6, as the parameter. |
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Ttelmah
Joined: 11 Mar 2010
Posts: 19545
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| Posted: Wed Jul 18, 2018 10:18 am |
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a couple of other comments:
setup_wdt(WDT_OFF);
This is a wasted instruction. You have the WDT turned off in the fuses. When it is turned off this way, the setup_wdt instruction cannot control it....
Then you have:
setup_vref(VREF_ON|VREF_ADC_1v024);
Why?. You are using Vss to Vdd as your reference, so all this does is turn the Vref on, and waste power.
As a note, this is actually not a usable setting. The minimum Vref for the ADC is 2.048. From the data sheet:
| Quote: |
ADC Reference Voltage (REF+) is the selected input, VREF+ pin, VDD pin or the FVR Buffer 1. When the FVR is selected
as the reference input, the FVR Buffer 1 output selection must be 2.048V or 4.096V (ADFVR<1:0> = 1x).
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The 1.048 setting is only really there for use with other peripherals. |
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Eddy71ua
Joined: 23 Sep 2009
Posts: 55
Location: Ukraine
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| Re: ADC PIC16F1823 ..half-work |
| Posted: Wed Jul 18, 2018 11:26 am |
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| PCM programmer wrote: |
That's not the correct way to set the A/D channel.
You must use the actual channel number, such as 3 or 6, as the parameter. |
Oops .. You're right, I was wrong.
| Quote: | Then you have:
setup_vref(VREF_ON|VREF_ADC_1v024);
Why?. |
Next, I measure the battery power.
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Ttelmah
Joined: 11 Mar 2010
Posts: 19545
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| Posted: Wed Jul 18, 2018 12:13 pm |
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| You still can't use the 1.024 volt setting. The _minimum_ voltage allowed for the voltage reference on the ADC is 1.8v. As I said the 1.024v setting is for other peripherals that can use the Vref source. |
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