CONFIG ADC

Action

Configures the A/D converter.

 

 

Syntax

CONFIG ADC = single, PRESCALER = AUTO, REFERENCE = opt

 

 

Remarks

ADC	Running mode. May be SINGLE or FREE.
PRESCALER	A numeric constant for the clock divider. Use AUTO to let the compiler generate the best value depending on the XTAL
REFERENCE	The options depend on the used micro. Some chips like the M163 have additional reference options. In the definition files you will find : ADC_REFMODEL = x This specifies which reference options are available. The possible values are listed in the table below.

 

 

Chip	Modes	ADC_REFMODEL
2233,4433,4434,8535,m103,m603, m128103	OFF AVCC	0
m165, m169, m325,m3250, m645,   m6450, m329,m3290, m649, m6490,m48,m88,m168	OFF AVCC INTERNAL or INTERNAL_1.1	1
tiny15,tiny26	AVCC OFF INTERNAL INTERNALEXTCAP	2
tiny13	AVCC INTERNAL	3
tiny24,tiny44,tiny85	AVCC EXTERNAL or OFF INTERNAL or INTERNAL_1.1	4
m164,m324,m644,m640,m1280, m1281,m2561,m2560	AREF or OFF AVCC INTERNAL1.1 INTERNAL_2.56	5
tiny261,tiny461,tiny861, tiny25,tiny45,tiny85	AVCC EXTERNAL or OFF INTERNAL_1.1 INTERNAL_2.56_NOCAP INTERNAL_2.56_EXTCAP	7
CAN128, PWM2_3,USB1287, m128, m16, m163, m32, m323, m64	AREF or OFF AVCC INTERNAL or INTERNAL_2.56	8
	You may also use VALUE=value

 

When you use VALUE=value, you may specify any value. The disadvantage is that when you port your code from one chip to another it will not work.

While the AREF, AVCC, etc. are all converter to the right settings, the value can not be converted.

 

 

The AD converter is started automatic when you use the CONFIG ADC command.

You can use STOP ADC and START ADC to disable and enable the power of the AD converter.

 

The GETADC() function is intended to be used with the SINGLE running mode. This means that each time you call GETADC(), a conversion is started. If you use the free running mode, you need to retrieve the value from the AD converter yourself. For example by reading the internal ADC word variable.

 

 

See also

GETADC , CONFIG ADCx

 

 

 

Example

'--------------------------------------------------------------------------------
'name : adc.bas
'copyright : (c) 1995-2005, MCS Electronics
'purpose : demonstration of GETADC() function for 8535 or M163 micro
'micro : Mega163
'suited for demo : yes
'commercial addon needed : no
'use in simulator : possible
' Getadc() will also work for other AVR chips that have an ADC converter
'--------------------------------------------------------------------------------
$regfile = "m163def.dat" ' we use the M163
$crystal = 4000000
 
$hwstack = 32 ' default use 32 for the hardware stack
$swstack = 10 'default use 10 for the SW stack
$framesize = 40 'default use 40 for the frame space
 
 
'configure single mode and auto prescaler setting
'The single mode must be used with the GETADC() function
 
'The prescaler divides the internal clock by 2,4,8,16,32,64 or 128
'Because the ADC needs a clock from 50-200 KHz
'The AUTO feature, will select the highest clockrate possible
Config Adc = Single , Prescaler = Auto
'Now give power to the chip
Start Adc ' NOT required since it will start automatic
 
'With STOP ADC, you can remove the power from the chip
'Stop Adc
 
Dim W As Word , Channel As Byte
 
Channel = 0
'now read A/D value from channel 0
Do
W = Getadc(channel)
Print "Channel " ; Channel ; " value " ; W
Incr Channel
If Channel > 7 Then Channel = 0
Loop
End
 
'The new M163 has options for the reference voltage
'For this chip you can use the additional param :
'Config Adc = Single , Prescaler = Auto, Reference = Internal
'The reference param may be :
'OFF : AREF, internal reference turned off
'AVCC : AVCC, with external capacitor at AREF pin
'INTERNAL : Internal 2.56 voltage reference with external capacitor ar AREF pin
 
'Using the additional param on chip that do not have the internal reference will have no effect.

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