Built-In Processors, Constants, and Switches (Part II)

Let’s improve on our previous example and add level control to the output signal.

In the previous example, the properties of Level() were fixed. What if we want to bypass the processor using a latching switch connected to digital input 1? Here’s how it is done:

DigitalIn[1] >> LevelSwitch;

# Property assignment to control the behaviour of Level()
Microphone
>> Level (
        gainType:       GainValue
        gain:           3.98
        offset:         0.0
        bypass:         LevelSwitch
)
>> MainOutput;

We could have also avoided declaring LevelSwitch and assigned DigitalIn[1] to bypass:

# Property assignment to control the behaviour of Level()
Microphone
>> Level (
        gainType:       GainValue
        gain:           3.98
        offset:         0.0
        bypass:         DigitalIn[1]
)
>> MainOutput;

DigitalIn_1 is a switch block declared in the platform descriptor file. Its input port is connected to a digital input hardware resource. The output port of DigitalIn_1 is of type boolean and can connect to the bypass port of gainDB().

We could also control the amplification/attenuation level of gainDB() by physically connecting a potentiometer to analog input 1 on the hardware and running the following program.

#Declare a control block labelled 'GainValue'

signal GainValue {
        default:        0.0
        rate:           ControlRate
        reset:          MasterReset
        meta:           'Gain level control with potentiometer at analog input 1'
}

# Connect 'ControlIn[1]' to input of 'GainValue' after value mapping
ControlIn[1]
>> Map (
        mode:           'Linear'
        minimum:        0.0
        maximum:        3.98
        bypass:         off
)
>> GainValue;

#Add variables to control the behaviour of gainDB
Microphone
>> Level (
        gainType:       'Linear'
        gain:           GainValue
        offset:         0.0
        bypass:         LevelSwitch
)
>> MainOutput;

ControlIn is a signal block declared in the platform descriptor file. Its input port is connected to an analog input hardware resource. The output port of ControlIn[1] is of type control real and can connect to the levelDB port of gainDB().

The values received by the input port of GainValueDB from the output port of ControlIn[1] are in the +/- 10.0 range. However, we would like to control the levelDB property of gainDB() between the values of -96.0 and 6.0 dB. This can be achieved through the mapping property of a control block by applying a linear transformation.

signal GainValueDB {
        default:        -96.0
        rate:           ControlRate
        reset:          MasterReset
        meta:           'Gain level control with potentiometer at analog input 1'
}

ControlIn[1]
>> Map (
        mode:           'Exponential'
        minimum:        -96.0
        maximum:        12.0
        bypass:         off
)
>> Round (
        mode:           'Truncate'
        increment:      0.1
        bypass:         off
)
>> GainValueDB;

Microphone
>> Level (
        gainType:       'Decibel'
        gain:           GainValueDB
        offset:         0.0
        bypass:         LevelSwitch
)
>> MainOutput;