Expansion Port
Expand Otii hardware capabilities: additional measurements or trigger external events
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Expand Otii hardware capabilities: additional measurements or trigger external events
Last updated
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The expansion port on the front of the Otii hardware is designed to enhance the hardware functionality, allowing users to measure additional voltages and currents or trigger external events. These enable complex testing setups, allowing users to expand measurement capabilities beyond standard power analysis, offering flexibility across diverse use cases from development to debugging.
Fourteen additional pins are available on the expansion port, which features multi-input and multi-output for analog and digital signals, serial communication, and additional power and ground points. Depending on the project requirements, these pins can be easily enabled and set up as needed within the Otii 3 Desktop App.
Note that the expansion port is designed to be identical across the Otii hardware versions, but capabilities in terms of voltage range, impedance and resolution differ from one version to the other.
The Otii Arc Pro features the following extension port:
RX
UART RX / Additional Digital Input (exclusively under scripting).
TX
UART TX / Additional Digital Output (exclusively under scripting).
GPI1
Digital Input #1
GPO1
Digital Output #1
GPI2
Digital Input #2
GPO2
Digital Output #2
SENSE+
Analog input with the AGND as reference/return.
SENSE-
Analog input with the AGND as reference/return.
ADC+
Differential input for current measurement. It also measures single-ended voltage with respect to AGND. Connect this input to the high side of the external shunt resistor
ADC-
Differential input for current measurement. Connect this input to the low side of the external shunt resistor
AGND
Analog ground. Return current / reference point for analog measuring.
DGND
Digital ground. Return current / reference point for digital signals.
+5V
5 V output (max 500 mA).
The serial ports known as RX (received data) and TX (transmitted data) enable serial communication between the Otii hardware and the Device Under Test (DUT) to provide real-time logs of how the code is impacting the battery draining. Moreover, these ports can be designated as GPIOs at the software level through the scripting feature using Otii Toolbox.
The digital I/O (GPIO) ports consist of six ports in total: two input ports and two output ports on the hardware level, plus additional input and output ports that can be set up on a software level by scripting.
These ports manage a voltage range from 1.2V to 5V, which can be set within the Otii 3 Desktop App. Check out the corresponding documentation to set up the ports according to your system's needs.
The chosen voltage level will be applied to all six (6) available digital I/O ports.
The analog ports consist of four analog inputs subdivided into two groups:
SENSE ports are general-purpose analog-to-digital inputs.
ADC ports are used to measure current over a shunt resistor.
General purpose analog to digital inputs enable voltage measurement using the AGND port as a reference. In addition, 4-wire measurements can be used to compensate for the voltage drop in the power supply leads.
Using the scripting feature—available with Otii Toolbox—one signal minus the other can be configured to measure differential voltages.
These ports manage a voltage input range of 0V to 5V with a 12-bit resolution and an input impedance >1 Mohm.
These ports are dedicated to measuring the current over a shunt resistor or the voltage from one node of the resistor with the AGND port as a reference; note that the voltage over the resistor is measured differentially. The ADC ports can manage either positive or negative currents.
These ports manage a single-ended voltage input range of 0V to 5V and a differential voltage range of -81.9175 mV to 81.2 mV, managing both voltage and current with 16-bit resolution.
The use case "Measuring a subsystem" is highly suggested to understand how to measure current over a shunt resistor, as well as the guidelines on how to choose the proper resistor.
The Otii Arc Pro provides three ground (GND) ports: one analog ground (AGND) port dedicated to analog measurements and two digital ground (DGND) ports dedicated to digital signals.
In addition, it has an additional 5V (max 500 mA) output voltage port that can be switched on and off as required via the Otii 3 Desktop App under the "CONTROL" section once the Otii Arc Pro is successfully connected. It can also be switched by the scripting feature using the Otii Toolbox.
Powering the Otii Arc Pro with a DC adapter is highly recommended if this pin is used for 5V output voltage.
Bitrate
110 bps
5.25 Mbps
Digital IO operating voltage
1.2 V
Vio ⁽⁷⁾
5 V ⁽⁸⁾
VIL Low-level input voltage. VIL
Vio*0.2V
VIH High-level input voltage
Vio*0.8V
Imax, Max sink/source current (total for GPIOs)
-10 mA
10 mA
Voltage input
0 V
5 V
Shunt voltage range
-81.9175 mV
81.2 mV
Resolution
2.5 µV
Accuracy
±(0.1% + 10 µV)
Input impedance
220 kΩ
Voltage input
0 V
5 V
Resolution
1.25 mV
Accuracy
±(0.1% + 7.5mV)
Input impedance
830 kΩ
Voltage input
0 V
5 V
Resolution
1.5 mV
Accuracy
1%
Input impedance
1 MΩ
Output voltage
5 V
Output current
500 mA
GPI1
Digital Input #1
0 V
5.5 V
GPO1
Digital Output #1
0 V
5.5 V
GPI2
Digital Input #2
0 V
5.5 V
GPO2
Digital Output #2
0 V
5.5 V
SENSE+
Analogue
0 V
5.5 V
SENSE-
Analogue
0 V
5.5 V
ADC+
Analogue
0 V
5.5 V
ADC-
Analogue
0 V
5.5 V
Do not exceed the minimum or maximum voltages on any port. This may cause damage to the Otii hardware.
