A2D not working on PIC16f

Hello All,

I am having trouble getting the A2D to work on PIC16f1939. I am using CCS compiler 5.007.
The CCS comes with the A2D function that works fine but when I follow the manual method( more control) I couldn't get it work.
Can anyone point out what I am doing wrong? your help is appreciated it.
Thank you!

Code ( (Unknown Language)):

1.  
2. #include <16F1939.h>
3. #device adc=10
4. #fuses   INTRC_IO, NOWDT, NOPROTECT, NOMCLR,VCAP_A6
5. #use     delay(clock = 32000000)//16000000)//8000000)
6. #include "flex_lcd.c"
7. #use     i2c(master, sda=PIN_C4, scl=PIN_C3)
8. #include <stdlib.h>
9. #use     fast_io (B)
10.  
11. #byte GPIOB = 0xd
12. #bit  GPIOB_1 = GPIOB.1
13.  
14. #byte TRISIOB  = 0x08D
15. #bit  TRISIOB_1=  TRISIOB.1
16.  
17. #byte ANSELB = 0x18D
18. #bit  ANSELB_1= ANSELB.1
19.  
20. #byte ADCON0=0x9d
21. #bit  ADCON0_0=ADCON0.0
22. #bit  ADCON0_1=ADCON0.1
23. #bit  ADCON0_2=ADCON0.2
24. #bit  ADCON0_3=ADCON0.3
25. #bit  ADCON0_4=ADCON0.4
26. #bit  ADCON0_5=ADCON0.5
27. #bit  ADCON0_6=ADCON0.6
28.  
29. #byte ADCON1=0x9e
30. #bit  ADCON1_7=ADCON0.7
31. #bit  ADCON1_6=ADCON0.6
32. #bit  ADCON1_5=ADCON0.5
33. #bit  ADCON1_4=ADCON0.4
34.  
35. //PERIPHERAL INTERRUPT ENABLE REGISTER 1
36. #byte PIE1= 0x91
37. #bit  PIE1_6=PIE1.6
38.  
39. #byte ADRESH=0x9c
40. #byte ADRESL=0x9B
41.  
42. //FUNCTION PROTOTYPE
43. void  adc_init(void);
44. int16 sample(void);
45.  
46. void  main()
47. {  
48.    int16 adc=0;
49.  
50.    lcd_init();
51.    adc_init();
52.  
53.    While(1)
54.    {
55.     adc=sample();
56.     delay_ms(10);
57.     printf(lcd_putc,"\f%s%5lu","ADC:",adc);
58.    }
59. }
60.  
61. void adc_init(void)
62. {
63.  
64.    //CONFIGURE PORT RB1/AN10 AS DIGITAL:
65.      TRISIOB_1=1; //CONFIGURE PIN RB1 AS INPUT.
66.  
67.    //CONFIGURE PIN AS ANALOG
68.       ANSELB_1=1;  // SET UP PIN RB1 AS ANALOG.
69.  
70.    //Select ADC conversion clock Fosc/64
71.       ADCON1_6=1;
72.       ADCON1_5=1;
73.       ADCON1_4=0;
74.  
75.    //Select Analog Channel 10 (AN10)
76.    //ADCON0 |=01010000;    
77.       ADCON0_6=0;
78.       ADCON0_5=1;
79.       ADCON0_4=0;
80.       ADCON0_3=1;
81.       ADCON0_2=0;
82.  
83.    //10 bit results should be right justified
84.     ADCON1_7=1;
85. }
86.  
87. int16 sample(void)
88. {
89.    // variable declaration
90.    int high;
91.    int low;
92.    int16 adc;
93.  
94.    //Disables the ADC interrupt
95.    PIE1_6=0;
96.    //Turn on the A2D converter
97.    ADCON0_0=1;
98.    //start the conversion (Go)
99.    ADCON0_1=1;
100.    //wait for the acquisition time
101.    delay_us(60);
102.  
103.    //when ADCON0_1=1 the A2D conversion is not done
104.    while(ADCON0_1==1)
105.    //wait till the conversion is finished
106.    //Read the value of ADRESH and ADRESL
107.    high= ADRESH;
108.    low=  ADRESL;
109.  
110.    //store the resulting A2D conversion
111.    //high and low byte into one 16 bit variable
112.    adc=make16(high,low);
113.  
114.    return(adc);
115. }
116.  
117.  

 

Thank you for your reply. I have followed your suggestions and I am still getting the result of the A2d as 65472 counts. I should be getting around 500 counts. Any other suggestions? Thanks again

I added a delay right after turning on the ADC ( 60us)
adc=10 is a predefined variable in the compiler. It tells the compiler we are using a 10 bit instead of 8bit mode.I found that this is not needed, so I removed it.

I am used to using different terminology for pins but you're right they should be in the header file.
the results of the adc is 10 bits. The variable that houses a 10 bit is a long variable. %5lu tells the printf that I am using a long variable with 5 digits.

 

It's working now, thanks again. It turnes out that eventhough the Vref- and Vref+ in ADCON1 are setup by default to '0' once I explicitly made them '0' I started getting the right result.
I never thought this step was necessary but it turned out it is.

Thanks again for the help and the tips