Murata DNT24 Series, Руководство по интеграции

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3.3 Digital I/O
The DNT24’s six digital (state) I/O ports are labeled GPIO0 through GPIO5. GPIO5 has an alternate function of /HOST_
RTS and GPIO4 of /HOST_CTS, providing hardware handshaking for the serial port and SPI slave mode operation. If se-
rial port hardware handshaking is not required and SPI slave mode is not enabled, GPIO4 and GPIO5 can be used for
other digital I/O functions. When SPI slave mode is enabled, GPIO5 and GPIO4
must be used for /HOST_RTS and
/HOST_CTS respectively, and GPIO3 must be used to provide the DAV signal (SPI slave mode overrides any other con-
figuration for these ports).
Except in SPI slave mode, GPIO0 through GPIO5 are available for customer-defined functions:
- The direction of each GPIO pin can be set for both active and sleep modes.
- The initial state (power on) of all GPIO pins configured as outputs can be set.
- The state of all GPIO pins configured as outputs in sleep mode can be set.
- GPIO triggering of I/O event reporting can be configured.
- GPIO level control of sleep hold-off can be configured.
See Section 5.3 for recommendations on configuring the digital I/O, and Sections 7.4.6 and 7.4.7 for
detailed information on GPIO parameters.
3.4 Analog I/O
The DNT24’s three ADC input channels are labeled ADC0 through ADC2. The ADC can be disabled if unused to reduce
current consumption. The ADC can be operated in either single-ended mode or differential mode. In single-ended mode,
up to three sensor inputs can be measured. The negative sensor
inputs are connected to ground and the positive sensor inputs are connected to ADC0, ADC1 and ADC2 respectively.
Single-ended measurements are unsigned 11-bit values. In differential mode, one or two sensor inputs can be measured
as 12-bit signed values. The first differential measurement is the difference between the voltage on ADC1 and the voltage
on ADC0, and is referred to as the ADC0 differential measurement. The second differential measurement is the difference
between ADC2 and ADC0, and is referred to as the ADC1 differential measurement. Operating the ADC in differential
mode takes advantage of common mode rejection to provide the best measurement stability. Differential mode also incor-
porates a programmable gain preamplifier function, with gains settings from 1 to 64 available.
There are two options for the ADC full-scale reference:
1. The DNT24 regulated supply voltage divided by 1.6, or about 2.06 V
2. A low impedance voltage source applied to the DNT24’s ADC_EXT_REF input pin, 2.7 V maximum. If no connec-
tion is made to this pin, a voltage equal to about 2.7 V will be present.
Note that when differential ADC mode is used, the maximum output voltage available from the preamplifier at any gain
setting is 2.4 V, so the maximum ADC reading that can be made using a 2.7 V ADC reference will be about 88.9% of full
scale. The ADC channels are read each ADC sample interval, which is configurable. High and low measurement thresh-
olds can be set for each ADC channel to trigger I/O event reporting messages.
The DNT24’s two DAC outputs are labeled DAC0 and DAC1. The DACs can be disabled if unused to reduce current con-
sumption. The DAC settings have 12-bit resolution. There are two options for the DAC full-scale reference:
1. The DNT24 regulated supply voltage, about 3.3 V
2. A low impedance voltage source applied to the DNT24’s ADC_EXT_REF input pin, 2.7 V maximum. If no connec-
tion is made to this pin, a voltage equal to about 2.7 V will be present.
See Section 5.4 for recommendations on configuring the analog I/O, and Sections 7.4.6 and 7.4.7 for
detailed information on analog I/O parameters.
©2009-2014 by Murata Electronics N.A., Inc.
DNT24 Integration Guide R2.0 - 10/27/14
www.murata.com