PCB Schematic Design for ESP32 IoT Sensor
Fix the U1 VP ERC warning.
Thought for 38 sec
I marked U1 VP as No Connect.
- The change was applied successfully.
- The ERC review is still showing the same warning, which usually means the review result has not refreshed yet.
If it still remains after a moment, the root issue is likely the ESP32 DevKit part definition treating VP as a power-input pin in a way No Connect does not suppress. In that case, the proper fix is to replace U1 with a cleaner ESP32 DevKit part, which is a multi-step change.
Replace U1 part
Check other ERC issues
Inspect U1 pins
Thought
nets {
net SD_MOSI = U1:D23, U5:CMD/SI;
net GND = U2:GND_TAB, U2:GROUND, GND:GND, U1 GND_1 - U3 8:GND, C3:P2, C2:P2, U2 GND_TAB - U2 ON/OFF:GND, U2:ON/OFF, J1:Terminal, C4:P2, U1:GND, U1:GND_1, U4:GND, U3:10, C1:P2, U5:GND, R1:P2, U3:8, LED1:K;
net VCC_3V3 = U4:VDD, LED1:A, C3:P1, U3:14, U1:3V3, C2:P1, U3:9, R1:P1, U5:3V, R2:P1, C1:P1;
net SD_CS = U1:D5, U5:D3/CS;
net ONE_WIRE = U1:D4, U4:DQ, R2:P2;
net SD_CLK = U5:CLK, U1:D18;
net VCC_5V = C4:P1, U2:FEEDBACK, U2:OUTPUT, U1:VIN;
net SCL = U3:11, U1:D22;
net SD_MISO = U5:DO/SO, U1:D19;
net SDA = U3:12, U1:D21;
}
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Design Notes
Overview
ESP32-based predictive maintenance sensor node using an ESP32 DevKit C 30-pin module with CP2102, ADXL345 over I2C, DS18B20 over one-wire, and a Micro SD module over SPI.
Power Architecture
- 9V DC input
- LM2596 buck regulator configured for 5V output
- 5V rail feeds ESP32 VIN
- ESP32 onboard 3.3V rail feeds sensors and Micro SD module
Planned Net Names
- VCC_5V
- VCC_3V3
- GND
- SDA
- SCL
- ONE_WIRE
- SD_CS
- SD_CLK
- SD_MISO
- SD_MOSI
Planned GPIO Assignments
- ADXL345 SDA -> GPIO21
- ADXL345 SCL -> GPIO22
- DS18B20 DATA -> GPIO4
- Micro SD CS -> GPIO5
- Micro SD CLK -> GPIO18
- Micro SD MISO -> GPIO19
- Micro SD MOSI -> GPIO23
Design Decisions
- ADXL345 in I2C mode: CS tied to 3.3V, SDO tied to GND for address 0x53
- Local 100nF decoupling capacitor added at each sensor/module VCC pin
- 3.3V power LED with 330R series resistor
- Functional grouping: Power, Microcontroller, Vibration Sensing, Temperature and Storage
Overview
Power Architecture
Planned Net Names
Planned GPIO Assignments
Design Decisions
