USB-I/O interface adapter has 5 analog inputs connected to 10-bit analog-to-digital converter (ADC). When you switch on the ADC module, the C.1, C.2, C.5, C.6 and B.3 pins automatically become analog inputs. You can use these inputs to measure voltage, current and resistance generated by wide range of analog sensors.
The ADC module converts an input voltage relative to voltage reference. The analog inputs may have a voltage range from VRefLow to VRefHi for making conversion. VRefLow can be either internal (the adapter negative supply voltage – VSS) or external (the voltage level on the C.5 pin). And VRefHigh can be either internal (the adapter positive supply voltage – VDD) or external (the voltage level on the C.6 pin). For more detailed information see Section 7.3, “Analog Reference Voltage”.
The ADC module is software controlled. Using ADC commands, you can enable/disable the ADC module and select the analog reference voltage. You can request the analog input value at any time. Besides, ADC module may periodically send events containing the analog input values. Or you can define limits (high and low threshold values) and ADC module will generate events when the threshold values are reached. For more detailed information about the ADC module events see Section 7.4, “ADC Event”.