SENA Rhio232 - Manual (Page 24)

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Figure 3-7 Connection of Digital Input Port
3.5.3 ADC Input Port
An ADC input port is a non-insulated input port. If possible, a circuit should be made using
AVCC (+5V) voltage supplied from internal circuits. When operating in Switch mode, a threshold
voltage should be specified. Input is set to ON and the ADC status LED is ON if the input
voltage is higher than the specified threshold value. Conversely, input is set to OFF and the LED
turns off when the input voltage is lower than the threshold. The ADC status LED operates only
when it is set as Switch mode.
1) Connecting reference voltage (AREF) in analog input
AREF can be set as either internal 2.56 V, internal AVCC or external AREF point. Internal input
can be set using command. The external input can be set by splitting the AVCC voltage into R1
and R2 as shown below. The ideal resistance of split resistors R1 and R2 should be within the
range of 1㏀ - 5㏀.
Note) AREF voltage cannot be set to the value less than 2 V.
Figure 3-8 Connecting Aref