16f88 - pin RA4 as analog input

**savnik** · - 29th October 2006, 12:07

I have the below code with 16f88 , and i want to know if may use the pin RA4
as analog input.
I want to read the voltage from a tuner.The range of voltage is 0.5-3.5V.

Code:

            CMCON = 7                                  ' PortA = digital I/O
             
	DEFINE LCD_DREG	PORTB	'Selection of the port B
	DEFINE LCD_DBIT 0	    'Selection one RB0 with RB3
	DEFINE LCD_RSREG PORTA	'RS on port A
	DEFINE LCD_RSBIT 2	    'RS on RA2
	DEFINE LCD_EREG	PORTA   'E on port A
	DEFINE LCD_EBIT 3	    'E on RA3
	DEFINE LCD_BITS 4		'Mode 4 bits
	DEFINE LCD_LINES 2	    '2 lines

	DEFINE I2C_SCLOUT 1
	
	PAUSE 500
	
' ** DEFINITION OF THE ENTREES - EXITS

' Exits I2C

	SCL var PORTA.1         'SCL on RA1 (pine 18)
	SDA	var	PORTA.0		    'SDA on RA0 (pin 17)

' Boutons

	UP	    var	PORTB.6		'increase the frequency (on RB6)
	DOWN	var	PORTB.7		'decrease the frequency (on RB7)
	CH_PAS	var	PORTB.5		'Change the step of synth (on RB5) 
 
	
	Input	UP			    'Up and Down are entries
	Input	DOWN
	Input	CH_PAS

**sayzer** · - 29th October 2006, 14:43

Hi Savnik,

RA4 can be used as analog input as data sheet says (16F88).

In this case, you need to add ANSEL = %00010000 to your code.
ANSEL = %00010000 will set RA4 as analog and all others as digital.
Make sure you set RA4 as an input pin prior to ANSEL.

You may need to work around CMCON a little.

------------------------

**savnik** · - 29th October 2006, 20:13

i have add this in my code:

Code:

    CMCON = 7               ' PortA = digital I/O
	ANSEL = %00010000       ' Will set RA4 as analog and all others as digital
    ADCON0 = %11100001	   
    ADCON1 = %10000010 	   
    adval   var Byte		     'Create adval to store result
    IN	    var	PORTA.4
    Input	IN

loop: 	ADCIN 0, adval					' Read channel 0 to adval

	    Lcdout $fe, 1   				' Clear LCD
        Lcdout "Value: ", DEC adval		' Display the decimal value  

        Pause 100       				' Wait .1 second

        Goto loop       				' Do it forever
        End

need to add this;

Code:

   
    Define  ADC_BITS        8     	' Set number of bits in result
    Define  ADC_CLOCK       3     	' Set clock source (3=rc)
    Define  ADC_SAMPLEUS    50    	' Set sampling time in uS

but show on LCD Value:3 continues

**Darrel Taylor** · - 29th October 2006, 22:26

Read from AN4

ADCIN 4, adval

**savnik** · - 30th October 2006, 06:33

Originally Posted by Darrel Taylor

Read from AN4

ADCIN 4, adval

Thank you.
At 0 volt show value: 0 and at 5 volt show value:3
How i can at 0 volt show value: 0 and at 5 volt show value: 50 or 100 or something greater from 3;
Is easy to show the level as bargaph on LCD;

**sayzer** · - 30th October 2006, 08:16

Post the schematic.
Let us see your ADC reading part also.

---------------------

**Darrel Taylor** · - 30th October 2006, 08:50

At 0 volt show value: 0 and at 5 volt show value:3

For 8 bit, you should Left justify the results.

ADCON1.7 = 0

**savnik** · - 30th October 2006, 09:30

Originally Posted by Darrel Taylor

For 8 bit, you should Left justify the results.

ADCON1.7 = 0

i have this

Code:

' Define ADCIN parameters
    
    DEFINE  ADC_BITS        8     	'Set number of bits in result
    DEFINE  ADC_CLOCK       3     	'Set clock source (3=rc)
    DEFINE  ADC_SAMPLEUS    50    	'Set sampling time in uS
    CMCON = 7                                'PortA = digital I/O    
    ANSEL = %00010000                   'Will set RA4 as analog and all others as digital     
    ADCON0 = %11100001	            'Configure and turn on A/D Module
    ADCON1 = %00000010 	            'Set PORTA analog and RIGHT justify result

and modify the result:
adval = adval*2/100
and at 0 volt show value: 0 and at 5 volt show value:5

**Darrel Taylor** · - 30th October 2006, 13:50

For 8-bit results, the largest number will be 255 at +5V.

255 * 2 = 510
510 / 100 = 5 (integer)

So let's assume you were trying to convert the A/D reading to a Voltage number.

<pre>255 * 5 / 255 = 5 ; Single digit 255 * 50 / 255 = 50 ; 1 decimal place (5.0) 255 * 500 / 255 = 500 ; 2 decimals (5.00)</pre>Those could also be done with the */ (Mid word) multiplication.<pre>255 */ 5 = 5 255 */ 50 = 50 255 */ 500 = 500</pre>Be sure to use WORD variables for the calculation.

Then to display it ...<pre>LCDOUT DEC value,"V" ; Single digit LCDOUT DEC value/10,".",DEC value // 10, "V" ; 1 decimal place LCDOUT DEC value/100,".",DEC value // 100, "V" ; 2 decimals</pre>

If you go with 2 decimals, you may want to use 10-bit values from the A/D for better accuracy.
In which case you would Right Justify, and the math changes to...<pre>1023 * 5 / 1023 = 5 ; Single digit 1023 * 50 / 1023 = 50 ; 1 decimal place 1023 * 500 / 1023 = 500 ; 2 decimals</pre>But you'll need to use DIV32 for those.

**savnik** · - 30th October 2006, 14:19

ADCIN 4, adval 'Read channel 4 to adval
adval1 = adval*2/100
adval2 = adval*4//10
Lcdout "POWER: ", DEC2 adval1, ".", DEC1 adval2," WATT "

I have use this code and show ok

**sayzer** · - 30th October 2006, 15:05

I was going to ask how would you see say 2.30V, but Darrel already touched that point.

Now I wonder where did this "Watt" come from?

Lcdout "POWER: ", DEC2 adval1, ".", DEC1 adval2," WATT "

---------------------

**savnik** · - 30th October 2006, 15:23

Originally Posted by sayzer

Now I wonder where did this "Watt" come from?

I measure the RF of a FM linear with a wattmeter.The output is in volt.
This volt i want to measure , and show on LCD.

**sayzer** · - 30th October 2006, 16:18

Ok, that makes sense now.

-----------------------------

**Darrel Taylor** · - 30th October 2006, 16:24

ADCIN 4, adval 'Read channel 4 to adval
adval1 = adval*2/100
adval2 = adval*4//10
Lcdout "POWER: ", DEC2 adval1, ".", DEC1 adval2," WATT "

I don't think that's what you want.

Let's say that you have 4.8 V on the input. You'll get an A/D reading of 249.

249 * 2 / 100 = 4   This part is ok
249 * 4 = 996, and //10 gives 6
So that would display as 4.6 instead of 4.8

Or if you had 4.2 V, (214 A/D)

214 * 2 / 10 = 4   Still OK
214 * 4 = 856, and //10 gives 6
Still displays as 4.6 instead of 4.2

Here are some more results

Code:

Volts	A/D	Whole#	4*A/D	//10	Result
5.00	255	5	1020	0	5.0
4.90	249	4	996	6	4.6
4.85	247	4	988	8	4.8
4.80	244	4	976	6	4.6
4.75	242	4	968	8	4.8
4.70	239	4	956	6	4.6
4.65	237	4	948	8	4.8
4.60	234	4	936	6	4.6
4.55	232	4	928	8	4.8
4.50	229	4	916	6	4.6
4.40	224	4	896	6	4.6
4.30	219	4	876	6	4.6
4.20	214	4	856	6	4.6

I think you should take another look at the formulas in post #9

**savnik** · - 30th October 2006, 16:40

Originally Posted by Darrel Taylor

I don't think that's what you want.

Let's say that you have 4.8 V on the input. You'll get an A/D reading of 249.

249 * 2 / 100 = 4   This part is ok
249 * 4 = 996, and //10 gives 6
So that would display as 4.6 instead of 4.8

Or if you had 4.2 V, (214 A/D)

214 * 2 / 10 = 4   Still OK
214 * 4 = 856, and //10 gives 6
Still displays as 4.6 instead of 4.2

Here are some more results

Code:

Volts	A/D	Whole#	4*A/D	//10	Result
5.00	255	5	1020	0	5.0
4.90	249	4	996	6	4.6
4.85	247	4	988	8	4.8
4.80	244	4	976	6	4.6
4.75	242	4	968	8	4.8
4.70	239	4	956	6	4.6
4.65	237	4	948	8	4.8
4.60	234	4	936	6	4.6
4.55	232	4	928	8	4.8
4.50	229	4	916	6	4.6
4.40	224	4	896	6	4.6
4.30	219	4	876	6	4.6
4.20	214	4	856	6	4.6

I think you should take another look at the formulas in post #9

You are right , but I don't understand how to write the code for the remainder to show right the decimal

**Darrel Taylor** · - 30th October 2006, 16:57

**savnik** · - 30th October 2006, 18:46

Originally Posted by Darrel Taylor

Thank you

**savnik** · - 31st October 2006, 09:32

Darrel Taylor,
thank you and for this thread : http://www.picbasic.co.uk/forum/show...light=bargraph
I use it to show to the second line on the LCD the volt as bargraph.

**savnik** · - 15th December 2006, 09:38

Originally Posted by Darrel Taylor

If you go with 2 decimals, you may want to use 10-bit values from the A/D for better accuracy.
In which case you would Right Justify, and the math changes to...<pre>1023 * 5 / 1023 = 5 ; Single digit 1023 * 50 / 1023 = 50 ; 1 decimal place 1023 * 500 / 1023 = 500 ; 2 decimals</pre>But you'll need to use DIV32 for those.

I want to use 10-bit values.
But i can use the DIV32 command to show the result on LCD.

Now for 8 bit i have this code:

Code:

    ADCIN 0, adval	                       ' Read channel 0 to adval
    value = adval*50/255                  ' 1 decimal place (5.0)
    
    LCDOUT $FE,1,"VOLT : ",DEC value/10, ".",DEC value//10, " V"

**savnik** · - 15th December 2006, 12:59

i use this:
ADCIN 0, adval ' Read channel 0 to adval
dummy = adval * 5 * 100 ' Multiply to load internal registers with 32-bit value
value = Div32 1023 ' Divide 32-bit value by word and store in word
Lcdout $fe,1, "VOLT : ", DEC value/10,".", DEC value//10, " V"

**CocaColaKid** · - 15th December 2006, 13:55

Why not use:

adcin 0, adval
adval = adval * 196 / 100
lcdout $fe,1, "VOLTS: ", DEC1 adval/100,".", DEC2 adval//100, " V"

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