16F876 A/D problems

[Francesc]

Hi all,
I need use an A/D connect on pin RA5 (Pin 7) and view results on LCD display connect to Port A and Port B (RB0 to RB7) and (RA0 to RA2).
When I connect on RA5 the voltage source not is possible regulate 0 to 5Volts.The voltage move directly 0 to 5V and 5V to 0V.
Also, when I connect the voltage tester on pin RA5 ( when not is connect voltage source), I measure 5 Volts.
That is my program, I supose what not is correctly configurate.

#include<16f873.h>
#device ADC=10
#USE DELAY(CLOCK=4000000,RESTART_WDT)
#INCLUDE <LCD2.C>
#USE FAST_IO(A)
#USE FAST_IO(B)
#USE FAST_IO(C)
#BYTE PORT_C=7

MAIN()
{
SETUP_ADC(ADC_CLOCK_INTERNAL);
LCD_INIT();
PORT_C=0;
SET_TRIS_C(0X00);

while(1)
{
RESTART_WDT();
SET_ADC_CHANNEL(4);
TEMP=READ_ADC();
DISPLAY(); //Routines for display value on LCD
DELAY_MS(100);
}
}
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This message was ported from CCS's old forum
Original Post ID: 7374

[Charlie U]

:=Hi all,
:=I need use an A/D connect on pin RA5 (Pin 7) and view results on LCD display connect to Port A and Port B (RB0 to RB7) and (RA0 to RA2).
:=When I connect on RA5 the voltage source not is possible regulate 0 to 5Volts.The voltage move directly 0 to 5V and 5V to 0V.
:=Also, when I connect the voltage tester on pin RA5 ( when not is connect voltage source), I measure 5 Volts.
:=That is my program, I supose what not is correctly configurate.
:=
:=#include<16f873.h>
:=#device ADC=10
:=#USE DELAY(CLOCK=4000000,RESTART_WDT)
:=#INCLUDE <LCD2.C>
:=#USE FAST_IO(A)
:=#USE FAST_IO(B)
:=#USE FAST_IO(C)
:=#BYTE PORT_C=7
:=
:=MAIN()
:={
:= SETUP_ADC(ADC_CLOCK_INTERNAL);
:= LCD_INIT();
:= PORT_C=0;
:= SET_TRIS_C(0X00);
:=
:= while(1)
:= {
:= RESTART_WDT();
:= SET_ADC_CHANNEL(4);
:= TEMP=READ_ADC();
:= DISPLAY(); //Routines for display value on LCD
:= DELAY_MS(100);
:= }
:=}

Please review section 11.0 of the F87x data sheet. This section explains the configuration limitations of the ADC. If you only want 1 analog input, it must be AN0 (RA0). You will need to switch the pin assignments around and control your LCD from other port A pins.

Hope this helps.
___________________________
This message was ported from CCS's old forum
Original Post ID: 7375

[Nicholas Kinnas]

:=Hi all,
:=I need use an A/D connect on pin RA5 (Pin 7) and view results on LCD display connect to Port A and Port B (RB0 to RB7) and (RA0 to RA2).
:=When I connect on RA5 the voltage source not is possible regulate 0 to 5Volts.The voltage move directly 0 to 5V and 5V to 0V.
:=Also, when I connect the voltage tester on pin RA5 ( when not is connect voltage source), I measure 5 Volts.
:=That is my program, I supose what not is correctly configurate.
:=
:=#include<16f873.h>
:=#device ADC=10
:=#USE DELAY(CLOCK=4000000,RESTART_WDT)
:=#INCLUDE <LCD2.C>
:=#USE FAST_IO(A)
:=#USE FAST_IO(B)
:=#USE FAST_IO(C)
:=#BYTE PORT_C=7
:=
:=MAIN()
:={
:= SETUP_ADC(ADC_CLOCK_INTERNAL);
:= LCD_INIT();
:= PORT_C=0;
:= SET_TRIS_C(0X00);
:=
:= while(1)
:= {
:= RESTART_WDT();
:= SET_ADC_CHANNEL(4);
:= TEMP=READ_ADC();
:= DISPLAY(); //Routines for display value on LCD
:= DELAY_MS(100);
:= }
:=}

Fist of all you need a setup_adc_ports statement to enable the correct A/D reference and tell the chip what inputs are to be used for analog. For example setup_adc_ports(ALL_ANALOG) will set all ports to analog and use vss and vdd as your rails, if you use something like setup_adc_ports(RA0_RA1_RA3_ANALOG)you are setting just these inputs as analog. Look in you 16f876.h file for all the available settings. You should also use setup_adc(ADC_CLOCK_DIV_8) instead of SETUP_ADC(ADC_CLOCK_INTERNAL) using the internal clock is not recommended for clock freqeuncies over 4mhz.
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This message was ported from CCS's old forum
Original Post ID: 7532