Wired 5 V and GND to the sensor, LCD interface, and support parts.
Connected Arduino I2C to the LCD interface: U1 SDA/SCL -> U3 SDA/SCL.
Connected DHT22 data: U2 DATA -> U1 D2 with R1 as a 10k pull-up to 5 V.
Added 100 nF decoupling with C1 and C2 across the 5 V rail.
Mapped the LCD in 4-bit mode through U3: P0->RS, P1->E, P4->D4, P5->D5, P6->D6, P7->D7.
Success criteria review
✅ The schematic now includes U1, LCD1, and U2 with the required support circuitry.
✅ Power and ground are distributed to the display path, sensor, pull-up, and decoupling parts.
✅ The I2C path and DHT22 data path are connected and ready for firmware work.
✅ The exact integrated 16x2 I2C LCD assembly was not available in the library, so I implemented the intended I2C LCD function using LCD1 plus U3, which preserves the required Arduino-to-I2C-display architecture.
Next steps
There are ERC warnings for intentionally unused pins on the Arduino board symbol and unused LCD/expander pins in this minimal implementation, but the required functional connections are in place. If you want, I can next clean this up further by adding explicit no-connect handling, a backlight current-limiting path, or moving on to layout preparation.
Temperature indicator using an Arduino Uno, a 16x2 LCD display controlled over an I2C interface, and a DHT22 temperature and humidity sensor.
Architecture
Diagram
Functional Requirements
Arduino Uno provides the 5 V rail and main controller logic.
DHT22 connects with VCC, GND, and a single digital DATA line.
DATA line includes a 10k pull-up to 5 V.
LCD is intended to be used through I2C using SDA and SCL from the Arduino Uno.
Minimal supporting capacitors are included for local decoupling and power stabilization.
Implementation Notes
Use Arduino Uno SDA and SCL pins for the display interface.
Use one Arduino digital GPIO for the DHT22 DATA signal.
Establish a common 5 V and GND network across all components.
If the exact integrated 16x2 I2C LCD assembly is unavailable in the library, use the closest available library representation and keep the intended I2C architecture documented here.