Pic18F452

[mister_e]

I can't tell anything about ADCOM As it doesn't exist, but let's try with ADCON0

If you plan to use PBP ADCIN, use my PicMultiCalc software. It make things easy. Let's say your OSC=20 MHz, your analog source impedance is 1K and you want to make a 10 Bit conversion, you need to add those DEFINEs at the top of your code

DEFINE ADC_BITS 10    ' ADCIN resolution  (Bits)
DEFINE ADC_CLOCK 2    ' ADC clock source  (Fosc/32)
DEFINE ADC_SAMPLEUS 3 ' ADC sampling time (uSec)

ADC_CLOCK 2 refer to ADCS1:ADCS0 bits (ADCON0<7:6>)

Sure you could even use the usual Frc and set your Sampling time to 50uSec and it will cover almost every possible situation.

Even by using the PicMultiCalc, you'll need to set the ADFM bit in ADCON1 register. Yeah i didn't include this in the software as Microchip change their mind in almost every new PIC. Maybe One day... maybe.

[mister_e]

Now, if you plan to NOT use ADCIN, you must do everything manually. Here's ashort example... OK OK it looks huge but...

        '
        '   PIC configuration fuses
        '   ========================
        asm
		__CONFIG    _CONFIG1H, _HS_OSC_1H
                                ; HS osc (20 MHz
                                ;		                          
		__CONFIG    _CONFIG2L, _BOR_ON_2L & _BORV_27_2L & _PWRT_ON_2L 
                                ; Enable Brown out voltage detect
                                ; Brown out voltage threshold 2.7 Volt
                                ;
		__CONFIG    _CONFIG2H, _WDT_OFF_2H
                                ; Disable watch dog timer
                                ;
		__CONFIG    _CONFIG3H, _CCP2MX_OFF_3H
                                ; Use default PORTC.1 for CCP2
                                ;
		__CONFIG    _CONFIG4L, _STVR_ON_4L & _LVP_OFF_4L & _DEBUG_OFF_4L
                                ; enable stack overflow
                                ; disable low-voltage programming mode
                                ; disable background debugger		  
                                ;
		__CONFIG    _CONFIG5L, _CP0_OFF_5L & _CP1_OFF_5L & _CP2_OFF_5L & _CP3_OFF_5L 
                                ; disable code protect (user block)
                                ;		                          
		__CONFIG    _CONFIG5H, _CPB_OFF_5H & _CPD_OFF_5H
                                ; disable code protect (boot block)
                                ;		
		__CONFIG    _CONFIG6L, _WRT0_OFF_6L & _WRT1_OFF_6L & _WRT2_OFF_6L & _WRT3_OFF_6L       
                                ; disable write protect (user block)
                                ;		                      
		__CONFIG    _CONFIG6H, _WRTC_OFF_6H & _WRTB_OFF_6H & _WRTD_OFF_6H
                                ; disable Write protect CONFIG regs 
                                ; disable write protect boot block
                                ; disable rite protect Data EE
                                ;
		__CONFIG    _CONFIG7L, _EBTR0_OFF_7L      
                                ; Disable table Read protect user block
                                ;
		__CONFIG    _CONFIG7H, _EBTRB_OFF_7H
                                ; Disable Read protect boot block enable
        endasm
                
        '
        '       Hardware configuration
        '       ======================
                '
        DEFINE OSC 20
                '
                '   Adc
                '   ---
        ADCON0 = %10000001                  ' Conversion clock = Fosc/32             
                                            ' AN0 selected   
                                            ' turn on ADC

        ADCON1 = %110001110                 ' right justified results
                                            ' Conversion clock = Fosc/32
                                            ' PORTA.0 as analog, all other to digital
        '
        '       Hardware assignment
        '       ===================
                '
                '   LCD
                '   ---
        DEFINE LCD_DREG PORTD               ' LCD data port 
        DEFINE LCD_DBIT 4                   ' LCD data starting bit 0 or 4 
        DEFINE LCD_RSREG PORTD              ' LCD register select port 
        DEFINE LCD_RSBIT 2                  ' LCD register select bit 
        DEFINE LCD_EREG PORTD               ' LCD enable port 
        DEFINE LCD_EBIT 3                   ' LCD enable bit 
        DEFINE LCD_BITS 4                   ' LCD bus size 4 or 8 
        DEFINE LCD_LINES 2                  ' Number lines on LCD 
        DEFINE LCD_COMMANDUS 2000           ' Command delay time in us 
        DEFINE LCD_DATAUS 50                ' Data delay time in us 

        '
        '       Alias definition
        '       ================
                '
                '   ADC
                '   ---
        GoDone  var ADCON0.2                ' use to start/stop/check 
                                            '       AD conversion
                                            
        ADON    VAR ADCON0.0                ' use to start/shut-off ADC

        '
        '       Variable definition
        '       ===================
        @AdResult = ADRESL    
        AdResult        var word EXT        ' Store ADC result
        
        '
        '       Software constants
        '       ==================
        ADC_SampleUs    con 3               ' ADC sampling time        
        
        '
        '       Program Start here
        '       ==================
        Pause 500                           ' LCD start up delay

Start:
                '
                '       A/D conversion
                '       --------------
        adon = 1                            ' turn on ADC
        pauseus adc_sampleus                ' Wait minimum sampling time
        godone = 1                          ' start conversion
        while godone : wend                 ' check if finished
                                            '
        adon = 0                            ' turn off ADC
                '
                '       Show result on LCD
                '       ------------------
        lcdout $FE,1, "Result=:", dec adresult 
                                            ' show result on LCD
        pause 250
        goto stART

[Lotondo]

Thanks Mister_E,
your explanation is well done but it's not easy to get it into
my head (hard).
I'll try to make some practical tests.
I'll take also a look to your prg.
Regards

Lotondo

[evilpic]

Well, hi everybody ...
It seems that you all know the basics of how to manage a 2x16 LCD with the famous 18f452 but i don't ..:'(
I really need to make it work for a project, but here's my problem, i have a pic trainer with the LCD configured to work with the high nibble data bus but it has the RS-->RB2, RE-->RB3 ,R/W-->gnd, and D4-D7 -->RB4-RB7 as you see all in the same portb, i gave on trying it myself. So please could anybody give me a code to display one message on the LCD. I wouldn't mind if you have it for a 16f877 as i have that one too. I know i may be asking too much, but please help me. Thanx
just in case one of you has mercy on my soul... my email is [email protected]

[GrandPa]

Mister e, you said

"ADC_CLOCK 2 refer to ADCS1:ADCS0 bits (ADCON0<7:6>)"

I would like to know where I can find information about this. Or ,maybe easier, can you explain how ADC_CLOCK is "translated" to Focs/32. Is this simply the decimal value of ADCS1:ADCS0 bits?

Thanks!

[Melanie]

GrandPa...

"ADC_CLOCK 2 refer to ADCS1:ADCS0 bits (ADCON0<7:6>)"

I would like to know where I can find information about this

You can find the information you seek and it's all explained in great detail in the DATASHEET for the PIC you are using. Download it from www.microchip.com and study...

Tip: NEVER program a PIC without first studying it's Datasheet.

evilpic...

No, you're not asking too much, but this is very basic stuff that you should be capable of figuring for yourself.

Take a look at the LCDOUT command located here... http://www.melabs.com/resources/pbpmanual/

Scroll down until you find the DEFINE statements and change them accordingly for your preferred hardware connections.

Tip: NEVER program anything without first studying the compiler manual.

[GrandPa]

Thank's Melanie, but I've actually read the datasheet and use it currently. I'm actually setting the ADCON0 register directly instead if using the define.

My question is very specific about the DEFINE ADC_CLOCK.
What I don't understand is the meaning of the parameter (number) after the define:

In the book you have :
DEFINE ADC_CLOCK 3 'ADC clock source (rc = 3)
WHY does 3 mean RC clock ?

And

Mister e wrote:
DEFINE ADC_CLOCK 2 ' ADC clock source (Fosc/32)
Why does 2 mean Fosc/32

After reading the datasheet, I came to the conclusion that this number is the binary values of ADCS0:ADCS2 (PIC18F4620 here). But I wanted to make sure. So let me ask again:

----> Is this the decimal value of ADCS0:ADCS2 ?


(btw: I'm french, trying my best to explain my question)

J-P