EP-0257

Level-Shift Shield for Arduino UNO Q

SKU: EP-0257

Description

The Level-Shift Shield for Arduino UNO Q is a bidirectional level translation shield purpose-built for the Arduino UNO Q platform. Featuring a standard Shield plug-and-play form factor, it stacks directly onto the mainboard. The core employs the Texas Instruments (TI) TXS0108EPWR, an 8-bit auto-direction sensing bidirectional voltage-level translator that enables seamless signal conversion between 1.2V–3.6V (VCCA) and 1.65V–5.5V (VCCB) without requiring direction control signals.

This shield equips the Arduino UNO Q's 5V logic system with reliable 3.3V peripheral interfacing capabilities, making it ideal for connecting I2C sensors, SPI modules, UART wireless communication devices, and other GPIO peripherals—completely eliminating risks of communication failures and device damage caused by logic level mismatches.

Special Design: The board features a rectangular central cutout that avoids obstructing the LED Matrix on the Arduino UNO Q mainboard, ensuring users can still directly observe the board's LED display status even with the Shield stacked on top.

Features

• Standard Arduino UNO Q Shield form factor, stacks directly with zero additional wiring
• 3× TI 8-bit auto-direction sensing translators, 24 channels total
• Rectangular central cutout preserves visibility of Arduino UNO Q mainboard LED Matrix
• 8-bit parallel conversion with fully independent per-channel operation
• Push-pull signals up to 110 Mbps (for SPI / UART / GPIO)
• Integrated 10 kΩ pull-ups, open-drain signals up to 1 Mbps
• Outputs capable of driving capacitive loads up to 50 pF
• Supports Partial Power-Down mode with automatic high-impedance I/O state
• Retains standard pin headers, allowing additional Arduino Shield stacking
• Color-coded headers (red/yellow/blue/black/white) for quick identification and wiring

Protection Features

Leveraging the TXS0108EPWR silicon architecture, the Level-Shift Shield for Arduino UNO Q provides the following hardware protections during operation:

• Logic Level Mismatch Protection： Automatically performs bidirectional translation between 1.2V–3.6V and 1.65V–5.5V, fundamentally preventing logic misinterpretation, communication failures, or permanent CMOS breakdown damage when 3.3V devices are connected to 5V systems.
• ESD Protection： Compliant with JESD22-A114 standard, providing 2000V Human Body Model (HBM) ESD protection to absorb electrostatic discharge during daily handling, safeguarding downstream sensitive sensors and communication modules.
• Overvoltage Tolerance Protection: Input pins tolerate up to 5.5V overvoltage, preventing internal chip structure damage from accidental misconnection or signal crosstalk.
• Power-Down Protection (Partial Power-Down): When either VCCA or VCCB is disconnected, the TXS0108E automatically places all I/Os in high-impedance state, blocking current backflow paths and preventing abnormal device startup or damage from reverse power supply through signal lines.
• Power Domain Isolation & Backflow Prevention: VCCA and VCCB are fully independent power domains; internal isolation mechanisms prevent high-voltage side transient noise from coupling to the low-voltage side, avoiding power backflow damage to precision 3.3V devices.
• Hot-Swap Surge Suppression: Built-in edge-rate acceleration and transient suppression circuitry reduces voltage spike impacts on the Arduino UNO Q microcontroller during live insertion and removal.

Interface Layout

Based on the physical board design, the interface layout is organized as follows:

• Left Side — Digital Level-Shift Area

Pin Label	Color	Function
GND	Black	Ground reference
3V3	Yellow	3.3V power output (low-voltage side)
5V	Red	5V power output (high-voltage side)
D0–D13	Blue	Digital I/O level-shifted channels (Arduino UNO Q D0–D13 mapped to 3.3V-compatible signals)

Three TXS0108EPWR devices provide level translation for all digital pins D0 through D13, with color-coded headers for quick identification and wiring.

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• Right Side — System & Analog Area

Upper Section (Green/Black Headers)

Pin Label	Color	Function
VIN	Green	Arduino UNO Q external voltage input (pass-through)
REF	Green	Voltage reference (pass-through)
RESET	Green	System reset (pass-through)
IOREF	Green	I/O reference voltage (pass-through)
BOOT	Green	Boot mode select (pass-through)
GND	Black	Ground reference (pass-through)

NOTE: System control pins are routed through via pass-through headers, maintaining full compatibility with Arduino UNO Q standard pinout.

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• Middle Section (Power Rails)

Pin Label	Color	Voltage	Current Capability
5V	Red	5.0V	Sourced from Arduino UNO Q regulated 5V rail
3V3	Yellow	3.3V	Sourced from Arduino UNO Q onboard 3.3V regulator

Dedicated power rail headers provide easy access for external 3.3V peripherals and modules.

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• Lower Section (White Headers)

Pin Label	Color	Function
A0	White	Analog input A0, level-shifted to 3.3V logic
A1	White	Analog input A1, level-shifted to 3.3V logic
A2	White	Analog input A2, level-shifted to 3.3V logic
A3	White	Analog input A3, level-shifted to 3.3V logic
A4	White	Analog input A4, level-shifted to 3.3V logic
A5	White	Analog input A5, level-shifted to 3.3V logic

Analog pins A0–A5 are routed through dedicated TXS0108E channels, enabling 3.3V sensor interfacing while preserving analog read capability on the Arduino UNO Q mainboard.

• Central Cutout

Feature	Description
Rectangular opening	Strategic cutout positioned directly above the Arduino UNO Q onboard LED Matrix
Purpose	Preserves full visual access to LED Matrix status indicators during Shield operation
Benefit	Eliminates need to remove Shield for visual debugging or status monitoring

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• Component Placement

Reference	Component	Package	Function
U1	TXS0108EPWR	TSSOP-20	8-bit level translator (Digital pins D0–D7)
U2	TXS0108EPWR	TSSOP-20	8-bit level translator (Digital pins D8–D13 + reserved)
U3	TXS0108EPWR	TSSOP-20	8-bit level translator (Analog pins A0–A5 + reserved)
C1–C8	Decoupling capacitors	0402/0603 VCCA/VCCB supply filtering per device
R1–R4	Pull-up/pull-down resistors	0402/0603	OE enable control and signal conditioning

Pin Mapping Summary

Arduino UNO Q Pin	Shield Channel	TXS0108E Device	Side A (3.3V)	Side B (5V)
D0 (RX)	CH1	U1	3.3V logic	5V logic
D1 (TX)	CH2	U1	3.3V logic	5V logic
D2	CH3	U1	3.3V logic	5V logic
D3 (PWM)	CH4	U1	3.3V logic	5V logic
D4	CH5	U1	3.3V logic	5V logic
D5 (PWM)	CH6	U1	3.3V logic	5V logic
D6 (PWM)	CH7	U1	3.3V logic	5V logic
D7	CH8	U1	3.3V logic	5V logic
D8	CH1	U2	3.3V logic	5V logic
D9 (PWM)	CH2	U2	3.3V logic	5V logic
D10 (PWM/SS)	CH3	U2	3.3V logic	5V logic
D11 (PWM/MOSI)	CH4	U2	3.3V logic	5V logic
D12 (MISO)	CH5	U2	3.3V logic	5V logic
D13 (SCK)	CH6	U2	3.3V logic	5V logic
A0	CH1	U3	3.3V logic	5V logic
A1	CH2	U3	3.3V logic	5V logic
A2	CH3	U3	3.3V logic	5V logic
A3	CH4	U3	3.3V logic	5V logic
A4 (SDA)	CH5	U3	3.3V logic / I2C	5V logic / I2C
A5 (SCL)	CH6	U3	3.3V logic / I2C	5V logic / I2C

Color Code Reference

Color	Category
Black	Ground (GND)
Yellow	3.3V power / low-voltage side reference
Red	5V power / high-voltage side reference
Blue	Digital I/O signals
Green	System control pass-through
White	Analog input signals

Typical Applications

• I2C bus peripherals: BMP280 barometric sensors, SHT30 temperature/humidity sensors, SSD1306 OLED displays, RTC modules;
• SPI communication devices: W25Q128 Flash storage, ILI9341 TFT displays, RC522 RFID readers, 3.3V SD card modules;
• UART wireless modules: ESP8266/ESP32 Wi-Fi modules, HC-05/HC-06 Bluetooth modules, LoRa wireless serial;
• GPIO digital peripherals: 3.3V relay drivers, PWM speed controllers, encoder interfaces;
• low-voltage modern sensors: 1.8V/2.5V image sensors, MEMS microphones, biosignal acquisition front-ends.

Usage Notes

Note	Description
VCCA ≤ VCCB	The A-side voltage must be less than or equal to the B-side voltage. Typically, the A-side connects to 3.3V and the B-side connects to 5V. Reversing this relationship will result in improper translation and potential device damage.
LED Matrix Visibility	The central rectangular cutout ensures full visibility of the Arduino UNO Q mainboard LED Matrix. This allows real-time debugging and status monitoring without removing the Shield.
Integrated Pull-Up Resistors	The TXS0108EPWR integrates 10 kΩ pull-up resistors on each channel. For I2C applications, external pull-ups are typically unnecessary unless driving long bus lines or heavily loaded networks.
Automatic Mode Adaptation	The TXS0108E automatically distinguishes between push-pull signals (SPI / UART / GPIO) and open-drain signals (I2C). No manual mode switching or direction control is required.
OE Enable Control	Each TXS0108E device features an Output Enable (OE) pin. Driving OE high enables translation on all 8 channels of that device. Driving OE low places the corresponding 8 channels into high-impedance state. Tie OE to VCCA if always-on operation is desired.
Power Supply Sequencing	Ensure stable power on both VCCA (3.3V) and VCCB (5V) rails before asserting OE high. Glitch-free power-up sequencing prevents transient bus contention.
Maximum Capacitive Load	Do not exceed 50 pF per channel to guarantee specified edge rates and signal integrity. Heavy loads may require buffer amplification.
Hot-Swap Precaution	While the TXS0108E provides surge suppression, avoid hot-swapping 3.3V peripherals under active communication to prevent data corruption. Power down the peripheral side when possible.
ESD Handling	Although 2000V HBM protection is provided, standard ESD precautions are recommended during handling and assembly to maximize long-term reliability.
I2C Bus Speed Selection	The integrated 10 kΩ pull-ups support standard-mode (100 kHz) and fast-mode (400 kHz) I2C. For fast-mode plus (1 MHz), verify bus capacitance and consider external pull-up optimization.
Unused Channels	Unused TXS0108E channels may be left floating or tied to a valid logic level on either side. Floating inputs will not cause device malfunction due to auto-direction architecture.

Installation Guide

Step 1: Pre-Installation Check

Before installing the Level-Shift Shield, verify the following:

• Ensure the Arduino UNO Q mainboard is powered off and disconnected from USB or external power.
• Confirm all pins on the Shield are straight and properly aligned—no bent pins.
• Check that the central cutout orientation matches the LED Matrix position on the Arduino UNO Q.

Step 2: Physical Installation

• Align the Shield's female headers with the male pin headers on the Arduino UNO Q.
• The USB connector side of the Shield faces the same direction as the Arduino UNO Q USB port.
• Gently press the Shield down evenly until all pins are fully seated and the boards are parallel.
• The central cutout should sit directly above the LED Matrix with no obstruction.

Step 3: Power Verification

• Connect the Arduino UNO Q to USB or external power via USB-C.
• Verify the 3V3 (yellow) and 5V (red) power rails on the Shield are active.
• Confirm the TXS0108E devices are receiving proper VCCA and VCCB supplies.

Step 4: Enable Translation

• The OE pins are tied to VCCA by default (always-on operation) via onboard pull-ups.
• If manual control is required, connect the OE pin of any TXS0108E to a digital output and drive HIGH to enable or LOW to disable that channel group.

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Usage Instructions

Basic I/O Level Translation

Connect any 3.3V digital peripheral to the corresponding blue header pin on the Shield:

Shield Pin	Arduino UNO Q Pin	Voltage on Peripheral Side
D0–D13 (blue)	D0–D13	3.3V logic levels
A0–A5 (white)	A0–A5	3.3V logic levels

Example: A 3.3V active-low push button connects between Shield D2 (blue) and GND (black). The Arduino reads LOW when pressed, HIGH when released—no voltage conflict occurs.

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I2C Bus Connection

The Arduino UNO Q uses A4 (SDA) and A5 (SCL), which are routed through U3 on the Shield:

Signal	Shield Pin	Connect To
SDA	A4 (white)	SDA of 3.3V I2C sensor/module
SCL	A5 (white)	SCL of 3.3V I2C sensor/module
GND	GND (black)	GND of sensor/module
3V3	3V3 (yellow)	VCC of sensor/module

Example: Connect a BMP280 pressure sensor:

• BMP280 VCC → Shield 3V3 (yellow)
• BMP280 GND → Shield GND (black)
• BMP280 SDA → Shield A4 (white)
• BMP280 SCL → Shield A5 (white)

Use the standard Arduino Wire.h library. The Shield handles all level translation automatically.

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SPI Bus Connection

SPI pins D10–D13 are routed through U2:

Signal	Shield Pin	Connect To
SS	D10 (blue)	CS of 3.3V SPI device
MOSI	D11 (blue)	DIN/SDI of 3.3V SPI device
MISO	D12 (blue)	DOUT/SDO of 3.3V SPI device
SCK	D13 (blue)	CLK of 3.3V SPI device

Example: Connect a W25Q128 Flash module:

• Flash VCC → Shield 3V3 (yellow)
• Flash GND → Shield GND (black)
• Flash CS → Shield D10 (blue)
• Flash DI → Shield D11 (blue)
• Flash DO → Shield D12 (blue)
• Flash CLK → Shield D13 (blue)

Use the standard Arduino SPI.h library at full speed—the Shield supports up to 110 Mbps.

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UART Serial Connection

Digital pins D0 (RX) and D1 (TX) are routed through U1:

Signal	Shield Pin	Connect To
RX	D0 (blue)	TX of 3.3V UART module
TX	D1 (blue)	RX of 3.3V UART module

Example: Connect an ESP8266 Wi-Fi module:

• ESP8266 VCC → Shield 3V3 (yellow)
• ESP8266 GND → Shield GND (black)
• ESP8266 TX → Shield D0 (blue)
• ESP8266 RX → Shield D1 (blue)

Use Serial.begin(115200) or higher baud rates. The Shield automatically translates both directions.

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Analog Sensor Interfacing

Analog pins A0–A5 support 3.3V sensor output:

Shield Pin	Arduino UNO Q Pin	Application
A0–A5 (white)	A0–A5	3.3V analog sensors, digital I/O, or I2C (A4/A5)

Note: For true analog voltage reading, the Arduino UNO Q internal ADC still references 5V or the AREF pin. The Shield translates logic levels but does not scale analog voltages. Ensure 3.3V analog outputs are within the ADC measurable range.

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Power Output Usage

The power rail headers supply regulated voltage for external peripherals:

Rail	Color	Voltage	Typical Use
5V	Red	5.0V	5V sensors, relay modules, servos
3V3	Yellow	3.3V	3.3V sensors, wireless modules, displays
GND	Black	0V	Common ground reference

• Current Budget: Do not exceed the Arduino UNO Q onboard regulator current limits (typically 150 mA for 3.3V rail, 500 mA total via USB). For high-current loads, use external power with common ground.

LED Matrix Monitoring

With the Shield installed:

• The central cutout provides unobstructed view of the Arduino UNO Q LED Matrix.
• Use the LED Matrix for runtime status indication, error codes, or animation feedback.
• No disassembly required for visual debugging.

Disassembly

• Power off and disconnect all cables from the Arduino UNO Q.
• Grasp the edges of the Level-Shift Shield firmly.
• Pull straight up evenly to avoid bending pins.
• Store in anti-static packaging if not in immediate use.

Gallery

TBD.

Package Includes

TBD.