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tssir
Joined: 14 Feb 2016
Posts: 24
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| ADC not working on simple 16F1705 program |
 Posted: Tue Feb 14, 2017 8:33 am |
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Hello,
I use 16f1705 on a large project, and i have strange behaviour from it's ADC. Returned value is always 1014(dec).
If i use ADC_CLOCK_DIV_2 instead of ADC_CLOCK_DIV_64, value is random (358, 851, ...). It is normal, due to bad sampling time. It seems working.
If i use TEMPERATURE_INDICATOR, value seems realistic.
But in normal configuration, reading AN3 returns 1014.
However i successfully used ADC on many pics and projects ...
Then, i try this simple program, with same hardware:
| Code: |
#include <16F1705.h>
#DEVICE ADC=10
#fuses INTRC_IO \
,NOWDT /* Disable WDT at start */ \
,PUT /* Enable power up timer. The Power-up Timer provides a nominal 64 ms time-out on POR or Brown-out Reset. The device is held in Reset as long as PWRT is active. The PWRT delay allows additional time for the VDD to rise to an acceptable level.*/ \
,NOMCLR,NOPROTECT \
,BROWNOUT_NOSL,BORV19 /* Brownout enabled during operation, disabled during SLEEP */ \
,NOCLKOUT,NOIESO,NOFCMEN, \
,NOWRT /* Program memory not write protected */ \
,NOPPS1WAY \
,ZCDDIS /* Zero-cross detect circuit is disabled at POR */ \
,NOPLLEN \
,NOSTVREN /* Stack full/underflow will cause reset */ \
,LPBOR /* Low-Power Brownout reset is enabled */ \
,NODEBUG,NOLVP
#use delay(clock=32MHZ)
#USE fast_io(A)
#USE fast_io(C)
// --------------------------------------------------------------------------------------
#define IO_LEDR PIN_C2
#define IO_LEDG PIN_C1
// --------------------------------------------------------------------------------------
#define TRIS_A (0b00011111)
#define PULLUPS_A (0b00000000)
#define TRIS_C (0b00011000)
#define PULLUPS_C (0b00000000)
// =========================================================================================================================================================
void main(void)
{
set_tris_a(TRIS_A);
set_tris_c(TRIS_C);
port_a_pullups(PULLUPS_A);
port_c_pullups(PULLUPS_C);
output_bit(PIN_C4,false);
output_bit(PIN_C5,false);
output_bit(IO_LEDR,true);
output_bit(IO_LEDG,true);
disable_interrupts(GLOBAL);
setup_adc_ports(sAN3,VSS_VDD); // sAN3 is RA4, pin 3
set_adc_channel(sAN3);
setup_adc(ADC_CLOCK_DIV_64);
while(true)
{
unsigned int16 tmp=read_adc();
// if(0) -> then red, tested
// if(1) -> then green, tested
if(tmp>((unsigned int16)0))
{
output_bit(IO_LEDG,false);
output_bit(IO_LEDR,true);
}
else
{
output_bit(IO_LEDR,false);
output_bit(IO_LEDG,true);
}
}
}
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If apply 0V on pin 3 (read 11mv on voltmeter), led is red.
If apply 1.18V on pin 3 (read 1.181V on voltmeter), led is red.
With this simple program, read_adc return 0 every times.
I check with a brand new PIC on breadboard : same result.
Working voltage is 3.3V. CCS 5.043
I can't see why. I'm going absolutely crazy. |
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Ttelmah
Joined: 11 Mar 2010
Posts: 19554
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| Posted: Tue Feb 14, 2017 8:51 am |
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set_adc_channel(sAN3);
Wrong. You don't use the define here, just the channel number.
set_adc_channel(3);
You are enabling sAN3, then trying to select ADC channel 32!....
(sAN3, is a 'bit mask', to enable the specific channel - happens to be 32)
So at present the input is not connected to anything. That you get apparently some result with clock/2, is just 'random', since the clock is then so fast that the ADC doesn't actually work.... |
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gaugeguy
Joined: 05 Apr 2011
Posts: 303
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| Posted: Tue Feb 14, 2017 8:54 am |
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Your test logic also appears flawed.
11mV with a 3.3V supply and 10 bit A/D is about 3.
1.18V is about 366.
Both of these are greater than 0 so the first test is true and IO_LEDG is false and IO_LEDR is true. |
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tssir
Joined: 14 Feb 2016
Posts: 24
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| Posted: Tue Feb 14, 2017 10:21 am |
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YES !!!!
Thank you very much.
I replaced a macro (define) by sAN3 for my test. It was wrong.
This small program works with :
set_adc_channel(3);
Now i can compare and search why my main program not working (other problem in my code, my business ... ).
Thank you, again ! |
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