BitsyXb - User Manual
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110118-0001A
4.3.2
ADSmartIO Features
The following are some of the functions that the ADSmartIO can perform. The functions actually
implemented depend on the firmware loaded on your system:
•
General purpose digital I/O and A/D
•
Keypad scan (section 4.3.6)
•
PS/2 keyboard input
•
Backlight on/off and brightness control (section 4.6.6)
•
Contrast control for display (enabled only when pixel clock is running) (section 4.6.7)
•
Read/set real-time clock (RTC) (section 4.2)
•
Wakeup via /RQOnOff signal (section 5.3.3)
•
Trickle-charge a battery (section 5.3.7)
•
Read a temperature sensor (section 4.3.5)
•
Monitor system power
•
Reset CPU
4.3.3
Digital I/Os
All available ports on the ADSmartIO controller can be individually configured as inputs or
outputs. If you write a "1" to an I/O port when it is configured as an input, it enables a pull-up
resistor. Electrical specifications are listed in section 6.3.6.
4.3.4
Analog Inputs (A/D)
Each of the Port A I/Os (PA0-PA7) includes an analog-to-digital (A/D) converter. The converters
give full-scale readings when the input voltage is equal to voltage reference Vref
(e.g. V=Vref
reading/1023). Not all ports are available for external A/D use; see section 4.3.7 for
port assignments. Electrical specifications are listed in section 6.3.6.
4.3.5
Temperature Sensing
The BitsyXb ADSmartIO can read the temperature of an external
thermistor connected across pins 5 and 7 of J3. The ADSmartIO
controller drives a transistor to energize the thermistor, then reads
the result through the voltage divider created by the thermistor (R
th
)
and an internal resistor (R
tl
). The thermistor circuit is shown at
right.
Electrical specifications for the temperature sensing circuit are
listed in section 6.3.6.
Vref
PD1
PA4
R
tl
J3
7
5
R
th
