oFreqL Object

A Hardware Object that generates and outputs a low frequency tone.

The following table lists the size and availability of the oFreqL Object.

	Object	Size	Description	A1	A2	B1	B2	C1
	oFreqL	5 Bytes	An Object that outputs a low frequency square wave on any I/O line.			x	x	x

Operation:

When the Operate property is 1, the oFreqL Object cycles the I/O line specified by the IOLine property at a rate specified by the Divisor property.

The Rate property is a clock divider value that specifies the frequency. The Frequency is derived from a 1,132kHz clock divided by 128 minus the value of the Rate property. [Frequency = 1132/(128-Rate)] For example, a Divisor of 120 will produce a frequency of 141.5Hz. [141.5 = (1132/(128-120))] If 0 is given as the Divisor, then the output is shut off. This is useful for some rudimentary low frequencies. If you need a higher frequency, see the oFreqH object. if you want music, see the oSoundgin object.

The Rate can be calculated for the desired frequency using the following formula: Rate = [128 - (1132 / Frequency)

The lowest frequency that can be generated is 8.913Hz [8.913 = (1132/(128-1))]
The highest frequency that can be generated is 1132Hz [1132 = (1132/(128-127))]

Note that the frequencies are not linear. This will be most noticeable at the higher frequencies.
(1132/1=1132Hz, 1132/2=566hz).

The actual output is done by inverting the state of the I/O Line. The result is a square wave output at the specified frequency. If two or more oFreqL Objects are set to the same I/O line, the output is effectively the two tones combined.

The oFreqL Object's output shares its timing with the rest of the ooPIC's multitasking objects. A large number of Objects running concurrently with the oFreqL Object can result in distortions on the higher frequency tones.

Properties:

The following table lists the properties of the oFreqL Object:

Property
Description

Rate

A value that specifies a 7-Bit divisor to a fixed frequency of 1132 kHz.

Object Class: oByte Value Range: 0 - 127 (MSB of byte not used)

Data Type: Numeric Default Value: 0

Determines the frequency using the following formula: Frequency = (1132/(128-Rate)

Rate Description

0 The square wave is disabled.

1 The square wave is generated at 8.913Hz.

2 The square wave is generated at 8.984Hz.

3-125 The square wave is generated at the specified frequency.

126 The square wave is generated at 566Hz.

127 The square wave is generated at 1132Hz.

IOLine

A value that specifies which I/O Line to output the square wave on.

Object Class: oIOLine Value Range: 0 - 31

Data Type: Numeric Default Value: 0

Some I/O Lines have special purposes. Be sure to see oIOLine help file for details.

Operate

A value that selects whether or not the square wave is outputted.

Object Class: oOperate Value Range: 0 - 1

Data Type: Numeric Default Value: 0

Operate Constant Description

0 cvOff The square wave is disabled.

1 cvOn The square wave is generated and outputted.

Address

Returns a pointer to the address of the oCounter Object instance.

Object Class: oAddress Value Range: 0 - 127

Data Type: Pointer (Read Only) Default Value: Address of Object

Examples:

In the following examples, the oFreqL Object is used.

' Produce an alarm every 
'  two seconds.

Dim T As New oFreqL

Sub Main()
  T.IOLine = 21
  Do
    Call Alarm
    ooPIC.Delay = 200
  Loop
End Sub

Sub Alarm()
  T.Operate = 1    
  Do 5 Times
    T.Divisor = 120
    ooPIC.Delay = 3
    T.Divisor = 117
    ooPIC.Delay = 3
  Loop
  T.Operate = 0
End Sub

' Combine 2 tones

Dim T As New oFreqL
Dim G As New oFreqL

Sub Main()
  T.IOLine = 21
  T.Divisor = 113
  T.Operate = 1
  G.IOLine = 21
  G.Divisor = 127
  G.Operate = 1
  Do 
    ooPIC.Delay = 15
    G.Operate = 0
    ooPIC.Delay = 15 
    G.Operate = 1
    G = G - 1
  Loop
End Sub