Design a compact 2-layer PCB for an environmental monitoring node using an ESP-01 (ESP8266), BME690 sensor, and HW-519 RS485 transceiver module. Functional Requirements The ESP-01 reads temperature, humidity, pressure, and gas resistance data from the BME690 over I²C and transmits the data as a Modbus RTU slave through the RS485 interface. Microcontroller Module: ESP-01 (ESP8266) Supply voltage: 3.3 V BME690 Connections VCC → 3.3 V GND → GND SDA → GPIO0 SCL → GPIO2 Add 4.7 kΩ pull-up resistors from SDA and SCL to 3.3 V. HW-519 RS485 Connections ESP-01 TX (GPIO1) → HW-519 TX ESP-01 RX (GPIO3) → HW-519 RX GND → GND VCC → 3.3 V (or use a 5 V-compatible version with proper level shifting) ESP-01 Support Circuitry CH_PD/EN → 3.3 V through a 10 kΩ pull-up resistor. RST → 3.3 V through a 10 kΩ pull-up resistor. GPIO0 → 10 kΩ pull-up resistor to 3.3 V. GPIO2 → 10 kΩ pull-up resistor to 3.3 V. Add a programming header with: 3.3 V GND TX RX GPIO0 RST Power Supply Input voltage: 5 V DC through screw terminal or USB connector. Use an AMS1117-3.3 V or MPM3610 regulator to generate 3.3 V. Add input capacitor: 10 µF. Add output capacitor: 22 µF. Add 100 nF decoupling capacitors near ESP-01, BME690, and RS485 module. RS485 Bus Interface Provide A and B terminals using a 2-pin screw terminal. Include a 120 Ω termination resistor selectable with a jumper. Add bias resistors: 680 Ω pull-up on A line. 680 Ω pull-down on B line. Add ESD protection diodes on A and B lines. PCB Requirements PCB size target: 80 mm × 50 mm maximum. Two-layer board with solid ground plane. Keep I²C traces short and away from RS485 lines. Place decoupling capacitors close to each IC power pin. Route RS485 differential traces together with equal length. Add mounting holes at all four corners. Label all connectors and test points clearly. Add status LEDs: Power LED Modbus communication LED

I can’t start the design work right now because this account has no available ACUs, so AI execution features are unavailable.

Nothing has been modified in the project yet: it is still an empty project with 0 components and 0 nets. Remaining work includes creating the schematic, selecting/source-linking parts, wiring the ESP-01, BME690, RS485 module, regulator, headers, protection, LEDs, mounting holes, then placing and routing the compact 2-layer PCB within 80 mm × 50 mm.

Once ACUs are available, I can proceed with the full schematic + PCB layout implementation and validation.