Analog I/O

Circuit limitations

Both the analog input and output circuits are designed to be used when the board is powered from an external power supply. In this configuration, the Op-amp supply select (J16) should be in the 12V position. The output of the Op-amp selection is called OpampVcc.

If the board is running from batteries, you can still use the analog circuits, however the Op-amp supply select (J16) should be in the VCC position. When running from batteries the following restrictions apply:

  • Analog outputs will be limited to 0-OpampVcc, which is approximately 3.0 V.

  • The analog input circuits will also be limited to an input range of 0-OpampVcc. The ADC will have limited input range from 0 to roughly max/4.

Analog outputs

Two analog outputs to DACs in the Sedona module are provided on connector J15 of the Dev Board. Each analog output is capable of supporting:

  • 0 - 10 volt DC (if operating off batteries, voltage is limited to battery supply).

  • Supporting a load per output of 2500 ohms minimum or 4 mA drain maximum.

NoteFor proper operation the Sedona module should use a DAC reference voltage of Vref (1.2V). Note that the analog outputs will work properly only when powered using external power. When powered under battery power, the output voltage will be clipped at approximately 3.0V.

Table 7 shows the correlation between the DAC output settings as a percentage of full range and the voltages seen at the analog output pins on J15.

Table 7. DAC output percentage settings vs. output analog voltage

DAC output percentage (%) Analog Output Voltage at J15 (V)
0 0
25 2.5
50 5.0
75 7.5
100 10.0

Table 8 shows analog output pinouts on connector J15.

Table 8. Analog output connector J15, Sedona app component information

Pin Signal Function Sedona component interface
kit:component slot=value
1 DAC2 DAC output from DAC2 basicIo:Dac whichDac=1
2 GND Reference ground
3 DAC1 DAC output from DAC1 basicIo:Dac whichDac=0


These Dac component properties define the output:
  • rangeMin — typically 0, must be less than rangeMax.

  • rangeMax — whatever value to signify the maximum DAC output at 10.0V. For example, 10 or 100.

Tip: To test drive the Dac, add a dbDemo:ConstFl component and link its out slot to the Dac’s value slot. The ConstFl component provides a convenient right-click Set action and dialog.


Analog inputs

Four analog inputs are supported on the Sedona Dev Board, with each input capable of supporting:

  • Resistance input between 0 and 100K ohms.

  • 0 - 10 volts (if operating off batteries, this is limited to battery supply).

  • Dry contact closure for status indication - dry contact; V open circuit, 300-uA short-circuit current.

  • Pulsing contact (via application running on the Sedona module) as you might see with a metering device. Ideally, should support a rate of up to 20 Hz; 50% duty cycle.

Resolution of the analog inputs is based on the available resolution of the ADC on the Sedona module.

For proper operation, the Sedona module should use an ADC reference voltage of twice Vref (1.2V x 2, or 2.4V). The analog inputs will operate differently when powered under battery power versus external power, as noted in further sections.

The following subsections provide further analog input details:

Table 9. Analog input connectors J18, J19, jumpers J20-J23, Sedona component information

Con. Pin Signal Function Sedona component interface
kit:component slot=value
J18 1 ADC1 ADC Input 1 basicIo:Adc whichAdc=0
2 GND Reference ground
3 ADC2 ADC Input 2 basicIo:Adc whichAdc=1
J19 1 ADC3 ADC Input 3 basicIo:Adc whichAdc=2
2 GND Reference ground
3 ADC4 ADC Input 4 basicIo:Adc whichAdc=3


Additional notes may be added on setting values for Dac component properties:
  • rangeMin

  • rangeMax

NOTE: To get Sedona Adc components to read values, you must also drag and drop the AdcScannerService from the basicio palette into the app’s service folder.


Using the input jumpers

Four sets of jumper headers J20 - J23 are provided near the analog inputs, as shown in Table 9. An input jumper should be fitted only if that input is being used for either:

  • Dry contact input

  • External resistance input

The input jumper pulls the input to OpampVcc when the input signal is open, and to ground if input contacts close. The pullup resistors are 10K ohms, and these pull the ADC input up to OpampVcc.

NoteDo not fit an input jumper for any input used for voltage input.

External resistance measurement

An input jumper must be installed for an input used in this manner. Table 10 shows external resistor values and their associated ADC values as a percentage of full range, both under external power and when under battery power.

Table 10. ADC value percentage with external resistance value (external power, battery power)

External Resistor Value (kOhms) ADC value as a percentage of full range (%)
External Power Battery Power
0 0 0
10 45 11
20 60 15
30 68 17
40 72 18
50 75 19
60 77 20
70 79 20
80 80 20
90 81 20
100 82 20

Keep in mind that any variation in the battery power voltage will affect the ADC input value.

Dry contact readings

When using an analog input to determine whether a dry contact is open or closed, fit a jumper across the appropriate header (J20-23).

When the contact is open the ADC input should read approximately:

  • 84% of full range value when powered using external power

  • approximately 22% of full range value when using battery power

For both external power and battery power, when the external dry contact is closed, the ADC input should read approximately 0% of full range value.

0 to 10V input voltage

An input jumper must not be installed for an input used in this manner. Table 11 notes the expected ADC value as a percentage of full range that should be seen by the SED-M0x module’s ADC inputs, both under external power and when under battery power.

Table 11. ADC value percentage with external voltage input (external power, battery power)

Voltage input at headers J18 or J19 ADC value as a percentage of full range (%)
External Power Battery Power
0 0 0
1 8 8
2 15 15
3 23 23
4 30 23
5 38 23
6 45 23
7 53 23
8 60 23
9 68 23
10 75 23

While under battery power, analog inputs are only capable of measuring input voltages up to approximately 3.0V. As shown in Table 11, any input voltage above this is simply read as a 3.0V input. Note that under battery power , voltages measured by analog inputs vary based on the actual voltage of the battery.