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DNT90 Integration Guide - 05/10/12
4. Reconfigure the ADC measurement interval as needed by setting the
AdcSampleIntvl
parameter.
The default is 100 ms, and applies to all ADC channels.
5. Set
the
AdcAveSelect
parameter to the number of ADC readings to be averaged to produce a
measurement. The larger the
AdcAveSelect
parameter is set, the greater the noise filtering effect,
but the longer it takes to produce a measurement. Setting this parameter to 8 or more when the
ADC is operating in single-ended mode is especially helpful in stabilizing ADC measurements.
6. Measurements on each ADC input can be compared to high/low threshold values, triggering an
I/O event report if the measurements go above/below the respective thresholds. The thresholds
for each ADC channel are set by loading the
AdcXThresholdLo
and
AdcXThresholdHi
, where
X
refers to the ADC channel designator, 0 through 2. When the ADC is operating in differential
mode, the ADC1 to ADC0 differential measurement is compared to the “0” high and low thresh-
olds, and the ADC2 to ADC0 differential measurements is compared to the “1” high and low
thresholds. In this case the “2” threshold values are not used.
7. Set
the
IoPreDelay
parameter as needed in Bank 6 to allow signals to stabilize following a mod-
ule wakeup event.
8. Set
the
AdcSkipCount
parameter in Bank 6 as needed to allow
internal
transients in the ADC
sample-and-hold circuit to settle out. This parameter must be set to at least 3 when
AdcDiffMode
is selected. Note that the
IoPreDelay
parameter discussed above provides a delay to allow sig-
nals
external
to the DNT90 to settle following an event, while
AdcSkipCount
skips measurements
that may be distorted because the
internal
voltage on the ADC sample-and-hold has not settled.
9. Select the DAC full scale reference by setting
DacReference
in Bank 6. This setting applies to
both DAC channels. The default is the ADC_EXT_REF input. If DAC operation is not needed, set-
ting this parameter to 0x03 will disable DAC operation, reducing current consumption.
10. Configure the initial (power on) output level for DAC0 and DAC1 by loading the initial settings in
the
Dac0Init
and
Dac1Init
parameters respectively.
The ADC and DAC channels are factory calibrated. It may be desirable to fine tune these calibrations
after the DNT90 has been integrated with the customer’s hardware in some applications. For analog
calibration support, contact RFM technical support.
5.5 Configuring I/O Event Reporting and I/O Binding
1. Select the analog, digital and timing events that will trigger an I/O event report by setting the
respective bits in the
IoReportTrigger
parameter in Bank 6. The default is no triggers set.
2. Configure the trigger behavior bits in the
GpioEdgeTrigger
parameter, Bank 6, for each GPIO
input selected to generate an I/O event report.
3. For each ADC channel selected to generate an I/O event, set the high and low measurement
threshold values. The
AdcThreshold
parameters are in Bank 6. When the ADC is operating in dif-
ferential mode, the ADC1 to ADC0 differential measurement is compared to the “0” high and low
thresholds, and the ADC2 to ADC0 differential measurements is compared to the “1” high and low
thresholds. In this case the “2” threshold values are not used.
4. If the periodic timer has been selected to generate an event report, load the required timer report
interval into the
IoReportInterval
parameter in Bank 6. The default timer interval is 30 seconds.
