Eurotech BitsyXb, User Manual

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BitsyXb - User Manual
40 110118-0001A
4.7 Discrete IOs
This section describes discrete signals on the BitsyXb that can be used for measurement and
control.
4.7.1 Digital IOs
The BitsyXb supplies a number of discrete digital I/Os for application use. These are referred to
as general-purpose digital inputs and outputs (GPIOs), as each discrete digital signal can be
configured as an input or as an output. The PXA270 and ADSmartIO controller drive the GPIOs
on the BitsyXb.
The cross-reference in section 4.1.6 is a complete list of all PXA GPIO ports. Section 4.3.7 lists
the usage of all ADSmartIO ports. Electrical specifications for PXA270 GPIOs are listed in
section 6.3.9, while section 6.3.6 lists ADSmartIO electrical specifications.
The following table lists the number of GPIOs available from each source, the series resistance,
whether the signals include ESD protection, the header number and notes about functions of the
port signals.
#
signals Source
Series
Resistance
ESD
prot. Header Usage Notes
5 PXA270
1 k Ω
Y J3 EIO5-9
5 PXA270
1 k Ω
Y J10 EIO0-4
5 ADSmartIO
1 k Ω
Y J10 PC0-4 or ROW0-4
4 ADSmartIO
1 k Ω
Y J10 PA0-3 or COL0-3
2 ADSmartIO
1 k Ω
Y J10
PD0 or Passive panel enable
PD1 or Thermistor energize
4.7.2 Analog Inputs
The BitsyXb uses the ADSmartIO controller to perform analog-to-digital (A/D) conversions.
These A/D inputs are typically used for low-speed, uncalibrated applications (e.g. user input,
ballpark voltage measurement, etc) as the noise margins on the BitsyXb A/Ds are not suited for
most instrumentation applications. For precision A/D readings, consider taking averages of
several readings, performing two-point calibrations or using an external A/D converter (e.g. over
SSP).
The following table summarizes the A/D inputs available on the BitsyXb. The Ref column
indicates reference sections for their use.
Range # lines Rin Source Header Ref Details
0–2.5 V up to 4 100 M Ω ADSmartIO J10
4.3.4,
6.3.6
PA0-3
0-2.5 V 1 100 M Ω ADSmartIO J3
4.3.4,
6.3.6
Thermistor (PA4)
4.7.3 Analog Outputs (PWM)
The BitsyXb has two filtered, pulse-width-modulated outputs that serve as analog control outputs.
These are used to control LCD backlighting and contrast (sections 4.6.6 and 4.6.7).