Polycom SoundStructure C16 Design Manual page 67

Logic Inputs
All digital logic inputs (logic inputs 1 - 22) operate as contact closures and may
either be connected to ground (closed) or not connected to ground (open). The
logic input circuitry is shown in the following figure. The default value for
logic inputs is 1 due to the pull up resistor. The value for the pin changes to 0
when the pin is shorted to ground. The value of the logic pin is read or written
with the digital_gpio_value parameter. See Chapter 9 and Appendix A for
more details.
SoundStructure Logic Input
Logic
Status
Analog Gain Input
The analog gain inputs (analog gain 1 and 2) operate by measuring an analog
voltage between the analog input pin and the ground pin. The maximum input
voltage level should not exceed +6 V. It is recommended that the +5 V supply
on Pin 1 be used as the upper voltage limit.
The next figure shows the analog gain input pin and the associated +5 V and
ground pins that are used with the analog gain input pin. The analog voltage
on the analog gain input pin is converted to a digital value via an ana-
log-to-digital converter for use within the SoundStructure devices. The
maximum voltage value, that is, 0 dBFS on the analog gain input, is 4.096 V.
0V is converted to 0 and 4.096 V and above is converted to 255.
SoundStructure Logic Input
Analog
Voltage
Value
SoundStructure Design Concepts
3.3V
Logic Input Pin
Logic Pin 25 (Ground)
5V Logic Pin 1 (+5V)
Analog Gain Input Pin
Logic Pin 25 (Ground)
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