Expansion Port

Expand Otii hardware capabilities: additional measurements or trigger external events

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.

Otii Arc Pro

The Otii Arc Pro features the following extension port:

Otii Arc Pro expansion port

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Pin	Description
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).

Serial ports

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.

Digital I/O ports

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.

Analog 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.

SENSE ports

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.

ADC ports

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.

Power & Ground ports

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.

Technical specifications

UART	Min	Typical	Max
Bitrate	110 bps		5.25 Mbps

DIGITAL I/O	Min	Typical	Max
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

Differential ADC, pins ADC- and ADC+	Min	Typical	Max
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

Single ended ADC, pins ADC- and ADC+	Min	Typical	Max
Voltage input	0 V		5 V
Resolution		1.25 mV
Accuracy		±(0.1% + 7.5mV)
Input impedance		830 kΩ

SENSE, pins SENSE- and SENSE+	Min	Typical	Max
Voltage input	0 V		5 V
Resolution		1.5 mV
Accuracy		1%
Input impedance		1 MΩ

EXPANSION PORT POWER SUPPLY	Min	Typical	Max
Output voltage		5 V
Output current			500 mA

Absolute maximum ratings

Pin	Description	Minimun Rating	Maximum Rating
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.

Otii Ace Pro

The Otii Ace Pro features the following extension port:

Otii Ace Pro expansion port

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Pin	Description
RX / GPI3	UART RX / Additional Digital Input #3 (exclusively under scripting)
TX / GPO3	UART TX / Additional Digital Output #3 (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.
0-15V	Adjustable output between 0V and 15V, max 600mA

Serial ports

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.

Digital I/O ports

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.

Analog 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.

SENSE ports

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 -10V to 25V with a 24-bit resolution and an input impedance >100 Mohm.

ADC ports

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 -10V to 35V and a differential voltage range of -102.4mV to 102.4mV, managing both voltage and current with 24-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.

Power & Ground ports

The Otii Ace 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 voltage output ranging from 0V to 15V (max 600mA), which can be switched ON or OFF, as needed, from the Otii 3 Desktop App under the "CONTROL" section once the Otii Ace Pro is successfully connected. It can also be switched by the scripting feature using the Otii Toolbox.

Powering the Otii Ace Pro with a DC adapter is highly recommended if this pin is used for 0-15V output voltage.

Technical Specifications

UART	Min	Typical	Max
Bitrate	50 bps		5.25 Mbps

DIGITAL I/O	Min	Typical	Max
Digital IO operating voltage	1.2 V	Vio ⁽⁷⁾	5 V
VIL Low-level input voltage			Vio*0.2V
VIH High-level input voltage	Vio*0.8V
Imax, Max sink/source current (total for GPIOs)	-10 mA		10 mA

Differential ADC, pins ADC- and ADC+	Min	Typical	Max
Voltage input	-10 V		25 V
Shunt voltage range	-102.4mV		102.4mV
Resolution		12.2nV
Accuracy		±(0.1% + 1µV)
Input impedance		>100Mohm

Single ended ADC, pins ADC- and ADC+	Min	Typical	Max
Voltage input	-10 V		25 V
Resolution		3.1µV
Accuracy		±(0.1% + 250 µV)
Input impedance		>100Mohm

SENSE, pins SENSE- and SENSE+	Min	Typical	Max
Voltage input	-10V		25 V
Resolution		3.1µV
Accuracy		±(0.1% + 250µV)
Input impedance		>100Mohm

EXPANSION PORT POWER SUPPLY	Min	Typical	Max
Output voltage	0V		15V
Output voltage setting resolution		5mV
Output current			600mA
Voltage between USB/DC jack & DGND/AGND	-200V ⁽²⁻³⁾		-200V ⁽²⁻³⁾

Absolute maximum ratings

Pin	Description	Minimun Rating	Maximum Rating
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	-10 V	25 V
SENSE-	Analogue	-10 V	25 V
ADC+	Analogue	-10 V	25 V
ADC-	Analogue	-10 V	25 V

Do not exceed the minimum or maximum voltages on any port. This may cause damage to the Otii hardware.