ReadAD10

Syntax:

For a normal ( also called a Single Channel ) read use.

    user_variable = ReadAD10( ANX )

For a Differential Channel read use the following. Where ANpX is the positive port, and ANnY is the negative port.

    user_variable = ReadAD10( ANpX , ANnY )

Command Availability:

When using ReadAD10 ( ANX ) the returned value is the full range of the ADC module then can be an 8 bit value [0-255]or an 10 bit value [0-1023]. The user variable can be a word, integer or long.

When using ReadAD10 ( ANpX , ANnY ), for differential ADC reading, the returned value is an integer as negative values can be returned.

ReadAD10 is a function that can be used to read the built-in analog to digital converter that many microcontroller chips include. The port should be specified as AN0, AN1, AN2, etc., up to the number of analog inputs available on the chip that is in use. Those familiar with Atmel AVR microcontrollers can also refer to the ports as ADC0, ADC1, etc. Refer to the datasheet for the microcontroller chip to find the number of ports available. (Note: it’s perfectly acceptable to use ANx on AVR, or ADCx on the microcontroller.)

Another function, ReadAD is similar to ReadAD10. The only difference is that it returns a byte variable.

AD_Delay controls is the acquisition delay. The default value is 20 us. This can be changed to a longer acquisition delay by adding the following constant.

    #define AD_Delay 4 10us

ADSpeed( controls the source of the clock for the ADC module. It varies from one chip to another. InternalClock is a microcontroller only option that will drive the ADC from an internal RC oscillator. The default value is 128.

    'default value
    #define ADSpeed MediumSpeed


    'pre-defined constants
    #define HighSpeed 255
    #define MediumSpeed 128
    #define LowSpeed 0

Example1 - Read 10-bit ADC

    #chip 16F819, 8
    #config osc = int


    'Set the input pin direction
    Dir PORTA.0 In


    'Print 255 reading
    For CurrentAddress = 0 to 255

        'Take a reading and show it
        Print str(ReadAD10(AN0))

        'Wait 10 minutes before getting another reading
        Wait 10 min
    Next

Example 2 - Reading Reference Voltages:

When selecting the reference source for ADC on ATmega328 Great Cow BASIC will overwrite anything that you put into te ADMUX register - but this option allow you change the ADC reference source on Atmel AVR microcontrollers. You can set the AD_REF_SOURCE constant to whatever you want to use. It defaults to the VCC pin, as example you can set the Atmel AVR to use the 1.1V reference with this: #define AD_REF_SOURCE AD_REF_256 where 256 refers to the 2.56V reference on some older AVRs, but the same code will select the 1.1V reference on an ATmega328p

    ' Dynamically switching reference.
    #define AD_REF_SOURCE ADRefSource
    #define AD_VREF_DELAY 5 ms
    AdRefSource = AD_REF_AVCC
    HSerPrint ReadAD10(AN1)
    HSerPrint ", "
    AdRefSource = AD_REF_256
    HSerPrint ReadAD10(AN1)

The example above sets the AD_REF_SOURCE to a variable, and then changes the value of the variable to select the source. With this approach, we also need to allow time to charge the reference capacitor to the correct voltage.

See Also ReadAD, ReadAD12