Schematic Design Review

sudaraka

sudaraka

just remove the esp32 from the circuit and instead use a pin header.

flux

I’ll replace the ESP32-C3 module interface with a simple pin header while preserving the existing signals for an external controller connection, then verify the schematic connectivity.

flux

Done — I removed the ESP32-C3 module U4 and replaced it with J2, a 1x08 external-controller pin header.
J2 pinout:
  • Pin 1: 3V3
  • Pin 2: GND
  • Pin 3: SDA
  • Pin 4: SCL
  • Pin 5: ALT
  • Pin 6: ADR
  • Pin 7: DQ
  • Pin 8: GND
Verification passed: the new header nets are connected and ERC checks showed no open schematic issues. I also updated Concise BOM - Part Name, Value, Designators and Circuit and Documentation Reverification.
Fix issues and verify
Add ALRT pull-up
Make pull-ups populated
Update all documentation
Run full review
Explain header wiring
U1
C7 P2 - R6 P1
U2 VDD - R7 P1
J1 Signal - R3 P1
R14 P1 - U1 ADDR
R8 P2 - U1 SCL
J5 GND - R10 P1
J1 GND - C6 P1
R10 P2 - C14 P2
U1 A0 - C11 P1
U2 VINB+ - R2 P1
J5 GND - R10 P1
U4 GPIO4 - J4 P1
U2 VDD - R7 P1
SW1 2 - J6 Pin_3
J1 GND - C6 P1
U1 A2 - C14 P1
U2 VDD - R7 P1
U1 A1 - R6 P2
U4 GPIO4 - J4 P1
U4 GPIO10 - U1 ALRT
J5 GND - R10 P1
U2 VDD - R7 P1
U2 VINB+ - R2 P1
R14 P1 - U1 ADDR
U2 VDD - R7 P1
J5 GND - R10 P1
R12 P1 - J5 Signal
C13 P1 - R12 P2
J1 GND - C6 P1
U1 A0 - C11 P1
R14 P1 - U1 ADDR
U1 A2 - C14 P1
R4 P1 - U2 VINB-
R8 P2 - U1 SCL
U2 VINB+ - R2 P1
R4 P1 - U2 VINB-
U4 GPIO8 - R7 P2
C13 P1 - R12 P2
R10 P2 - C14 P2
SW1 2 - J6 Pin_3
U2 VDD - R7 P1
J1 Signal - R3 P1
USB5
C13 P1 - R12 P2
U1 A1 - R6 P2
C7 P2 - R6 P1
U1 A2 - C14 P1
U1 A0 - C11 P1
U3 VOUTB - R13 P1
R5 P1 - U2 VINA-
C7 P1 - U2 VINA+
U4 GPIO4 - J4 P1
U2 VDD - R7 P1
C7 P2 - R6 P1
U2 VDD - R7 P1
BAT
J1 GND - C6 P1
U4 GPIO8 - R7 P2
U3 VOUTA - R9 P1
U3 VOUTB - R13 P1
J5 GND - R10 P1
R10 P2 - C14 P2
U4 GPIO4 - J4 P1
C7 P1 - U2 VINA+
U2 VDD - R7 P1
U1 A2 - C14 P1
U2 VDD - R7 P1
U2 VDD - R7 P1
U1 A0 - C11 P1
U2 VDD - R7 P1
U2 VDD - R7 P1
U1 A1 - R6 P2
U4 GPIO10 - U1 ALRT
U2 VINB+ - R2 P1
R8 P2 - U1 SCL
C7 P1 - U2 VINA+
U1 A1 - R6 P2
U2 VINB+ - R2 P1
R12 P1 - J5 Signal
U3 VOUTA - R9 P1
R5 P1 - U2 VINA-
U4 GPIO8 - R7 P2
U2 VDD - R7 P1
R10 P2 - C14 P2
C4
Capacitance
1 µF
R12
Resistance
1000000 Ω
R3
Resistance
1000000 Ω
R11
Resistance
4700 Ω
C1
Capacitance
100 nF
C8
Capacitance
100 nF
R6
Resistance
1000 Ω
R5
Resistance
1000 Ω
R10
Resistance
1000 Ω
C2
Capacitance
100 nF
C10
Capacitance
100 nF
R9
Resistance
1000 Ω
C6
Capacitance
100 nF
R8
Resistance
10000 Ω
C11
Capacitance
100 nF
R14
Resistance
10000 Ω
C7
Capacitance
100 pF
C13
Capacitance
100 pF
R4
Resistance
1000 Ω
R13
Resistance
1000 Ω
R2
Resistance
100000 Ω
C16
Capacitance
100 nF
C14
Capacitance
100 nF
C12
Capacitance
100 nF
C9
Capacitance
100 nF
R1
Resistance
100000 Ω
C3
Capacitance
10 µF
C5
Capacitance
10 µF
C15
Capacitance
100 nF
R7
Resistance
10000 Ω
GND
GND
R14 P2 - J2 8
GND
J1
GND
GND
U3 VSS - C15 P2
GND
J3 Pin_3 - J4 P2
GND
C11 P2 - C12 P2
GND
J3
U3 VSS - C15 P2
J2
GND
GND
C11 P2 - C12 P2
GND
U2
U3 VSS - C15 P2
U3
J5
J3 Pin_3 - J4 P2
GND
R14 P2 - J2 8
J6
J4
SW1

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Schematic and Documentation Reverification
Date: 2026-07-11 Project: ESP32-C3 ADS1115 pH ORP Sensor Interface 4412
Scope
This reverification checked the current schematic/netlist, automated ERC/passive/component-review checks, and the existing project files. Findings below are limited to issues observable in the current schematic or direct documentation mismatches.
Current Automated Check Status
The selected ERC/passive/component checks returned no open ERROR/WARNING/UNCERTAIN/OPEN items at the time of review. In particular, the automated checks did not flag floating pins, power-pin faults, shorts, undriven nets, missing decoupling, resistor power, capacitor voltage, pull-up/pull-down, or parts-available issues.
This does not clear design-intent issues that depend on ESP32-C3 boot behavior, exact module identity, or stale documentation.
Current Schematic Connectivity Observed
Main blocks
  • U4 ESP32-C3 Supermini is powered from 3V3 on U4:3V3; U4:5V is not part of the active power net.
  • U1 ADS1115 Module is powered from 3V3 and GND.
  • U2 and U3 MCP6002-I/P op amps are powered from 3V3 and GND.
  • J6 is an external power-module header: USB5 only connects to J6 pin 1, BAT only connects to J6 pin 2, and 3IN connects J6 pin 3 to SW1 pin 2.
  • SW1 connects the external 3IN rail to the board 3V3 rail through pins 2 and 1.
Digital/control nets
  • SDA: U1 SDA, U4 GPIO8, R7 P2.
  • SCL: U1 SCL, U4 GPIO9, R8 P2.
  • DQ: J3 pin 2, J4 P1, U4 GPIO4, R11 P2.
  • ADR: U1 ADDR, R14 P1, U4 GPIO5.
  • ALT: U1 ALRT, U4 GPIO10.
Analog nets
  • pH path: J1 center PHE -> R3 -> PHI -> U2A buffer -> PHB -> R5 -> PH+ -> U1 A0; biased reference PHR -> R6 -> PH- -> U1 A1.
  • ORP path: J5 center ORE -> R12 -> ORI -> U3A buffer -> ORB -> R9 -> OR+ -> U1 A2; biased reference ORR -> R10 -> OR- -> U1 A3.
  • VBD is formed by R1/R2 and filtered by C4; U2B and U3B buffer this bias into VBI and VBO.
Confirmed Schematic-Level Issues
1. I2C remains connected to ESP32-C3 boot/strap-sensitive pins
Observed current schematic:
  • SDA connects to U4:GPIO8.
  • SCL connects to U4:GPIO9.
The existing schematic review correctly identifies GPIO8/GPIO9 as ESP32-C3 boot/strapping-sensitive pins. This remains unchanged in the current schematic.
Actionable correction:
  • Move I2C to non-strap pins on U4, such as GPIO6/GPIO7 if those are available in the selected ESP32-C3 Supermini pinout and not otherwise used.
  • Update firmware pin definitions and all documentation after the schematic move.
2. Baseboard I2C pull-ups are optional/DNP, so I2C pull-ups are not guaranteed by the BOM
Observed current schematic:
  • R7: 10 kΩ from 3V3 to SDA, Exclude from BOM: true.
  • R8: 10 kΩ from 3V3 to SCL, Exclude from BOM: true.
  • U1 is labeled ADS1115 Module, but the exact module identity is not controlled by a real purchasable module MPN/datasheet in the schematic.
Actionable correction:
  • Either include R7/R8 in the BOM as fitted pull-ups, or specify the exact ADS1115 module with documented onboard pull-ups.
  • If both module pull-ups and baseboard pull-ups may be fitted, document the resulting parallel pull-up value and confirm it is acceptable for the bus.
3. ADS1115 ALRT/RDY is connected to GPIO10 but has no schematic pull-up
Observed current schematic:
  • ALT connects only U1 ALRT and U4 GPIO10.
  • No resistor from ALT to 3V3 is present.
Because the alert/ready pin is wired to the MCU, the schematic should define how it reaches a valid high state.
Actionable correction:
  • Add a 4.7 kΩ to 10 kΩ pull-up from ALT to 3V3, or explicitly mark ALT as firmware-internal-pull-up required.
  • If ALERT/RDY will not be used, disconnect/NC it instead of routing it as an apparently usable signal.
4. U1 implementation is still ambiguous: module symbol but bare-family metadata
Observed current schematic:
  • U1 part name: ADS1115 Module.
  • U1 MPN: ADS111X, a family label rather than an exact part/module.
  • U1 package/case: 10-VSSOP, which describes the bare IC package, not a typical header breakout module.
  • U1 role details rely on likely onboard 103 pull-ups from a user photo.
Actionable correction:
  • Choose and document one controlled implementation:
    • exact ADS1115 breakout module with verified header pinout, onboard pull-ups, and footprint; or
    • bare ADS1115 IC with correct IC footprint and all required external support circuitry included on this board.
5. Power entry remains external-module-dependent and should be clearer on the schematic
Observed current schematic:
  • USB5 and BAT are singleton nets at J6 pins 1 and 2.
  • The active board rail enters through J6 pin 3 as 3IN, passes through SW1, then becomes 3V3.
  • There is no onboard charger, battery protection, regulator, or power-path circuitry.
Actionable correction:
  • If intentional, add a schematic note at J6: “External power module required; J6 pin 3 must be regulated 3.3 V.”
  • If the board is meant to be standalone battery-powered, add the missing charger/protection/regulator circuitry.
6. ESP32-C3 Supermini is powered by its 3V3 pin, not the documented 5V input path
Observed current schematic:
  • U4 3V3 is connected to the board 3V3 rail.
  • U4 5V is not connected.
This can be valid only if the external rail is a regulated 3.3 V rail and the module supports direct 3V3-pin powering in the intended usage.
Actionable correction:
  • Add a note that the board must be powered only from regulated 3.3 V when U4 is populated this way.
  • Avoid simultaneous USB/module power unless the module power architecture is confirmed safe for backfeed conditions.
7. BNC shell pins are named GND in the connector symbols while intentionally biased above ground
Observed current schematic:
  • J1 shell/mechanical pins are symbol pins named GND but connect to PHR, not the schematic GND net.
  • J5 shell/mechanical pins are symbol pins named GND but connect to ORR, not the schematic GND net.
  • The component role notes correctly say these pins are biased reference nodes, not ground.
Actionable correction:
  • Rename/annotate connector pins as SHIELD, SHELL, or BIASED_SHIELD if the part can be edited.
  • Place a visible schematic note near J1/J5: “BNC shell/reference pins are biased nodes, not system GND.”
Items Verified as Coherent in the Current Schematic
  • The pH and ORP differential ADS1115 channel mapping is coherent: pH uses A0-A1, ORP uses A2-A3.
  • U2A/U3A are configured as voltage followers for the probe center inputs.
  • U2B/U3B are configured as voltage followers for the mid-supply bias node.
  • DS18B20 header J3 is coherent: pin 1 3V3, pin 2 DQ, pin 3 GND; R11 pulls DQ to 3V3.
  • Local decoupling/bulk capacitors are represented for U1, U2, U3, and the rail/bias nodes.
  • No LED components were found, so no missing LED current-limit resistor issue is present in the current schematic.
Documentation Reverification Findings
Firmware Starter - ESP32-C3 pH/ORP ADS1115
This file mostly matches the current schematic for SDA, SCL, and DQ, but has two direct mismatches:
  • It says ALT is optional but does not identify the current schematic connection to U4 GPIO10.
  • It says ADR is none/pulled low only, but the current schematic connects ADR to U4 GPIO5 as well as R14.
It also preserves the current GPIO8/GPIO9 I2C assignment, which matches the schematic but conflicts with the confirmed schematic review recommendation to move I2C off strap-sensitive pins.
ESP32-C3 ADS1115 pH/ORP Sensor Validation and Firmware Handoff Report
This file is partly current but has stale references:
  • It describes the ESP32-C3 header as J2; the current schematic uses U4 for the ESP32-C3 Supermini and does not show J2 as the active MCU header.
  • It maps ALT and ADR as optional header-style signals, but the current schematic connects ALT to U4 GPIO10 and ADR to U4 GPIO5.
  • It recommends/records GPIO8/GPIO9 I2C and treats that as acceptable if not forced low, while the later schematic review flags this as an issue to correct.
ADS1115 pH Sensor Design Notes
This file is substantially stale relative to the current schematic:
  • It describes an Arduino/5 V design, but the current schematic is ESP32-C3/3.3 V.
  • It says J3 pin 1 and R11 pull-up use VCC_5V; the current schematic uses 3V3.
  • It describes ADS1115 A2/A3 as auxiliary channels; the current schematic uses A2/A3 for ORP differential measurement.
  • It describes J2 Arduino/header pin maps and VCC_5V/I2C_SDA/I2C_SCL style nets, while the current schematic uses U4 and short nets 3V3, SDA, SCL, etc.
Actionable correction: mark this file as historical/obsolete or update it to the current ESP32-C3 + ORP design.
ESP32 and Arduino Uno Datasheet Summary
This file is general background and not fully current project documentation:
  • It compares Arduino Uno, classic ESP32-WROOM-32, and ESP32 DevKit usage rather than the current ESP32-C3 Supermini design.
  • It contains many 5 V Arduino and classic ESP32 pin recommendations that should not be treated as the current wiring map.
Actionable correction: keep it only as background, or add a top note saying it is not the authoritative current project pinout.
Schematic-Level Design Review
This file remains aligned with the current schematic. The same main issues are still present: GPIO8/GPIO9 I2C, optional/DNP I2C pull-ups, no ALT pull-up, ambiguous U1 identity, external-module-dependent power path, direct U4 3V3 powering, and misleading BNC shell pin names.
  1. Move I2C from U4 GPIO8/GPIO9 to safer ESP32-C3 GPIOs and update firmware/docs.
  2. Decide whether R7/R8 are fitted baseboard pull-ups or the exact ADS1115 module provides guaranteed onboard pull-ups.
  3. Add/annotate the ALT pull-up or remove the ALT MCU connection if unused.
  4. Replace or fully specify U1 as either an exact ADS1115 module or a bare ADS1115 IC implementation.
  5. Add explicit schematic notes for J6 power requirements and U4 direct-3V3 powering.
  6. Rename/annotate biased BNC shell pins.
  7. Update the firmware and handoff files so they no longer conflict with the current schematic.

  • Scope

  • Current Automated Check Status

  • Current Schematic Connectivity Observed

  • Main blocks

  • Digital/control nets

  • Analog nets

  • Confirmed Schematic-Level Issues

  • 1. I2C remains connected to ESP32-C3 boot/strap-sensitive pins

  • 2. Baseboard I2C pull-ups are optional/DNP, so I2C pull-ups are not guaranteed by the BOM

  • 3. ADS1115 `ALRT/RDY` is connected to GPIO10 but has no schematic pull-up

  • 4. U1 implementation is still ambiguous: module symbol but bare-family metadata

  • 5. Power entry remains external-module-dependent and should be clearer on the schematic

  • 6. ESP32-C3 Supermini is powered by its `3V3` pin, not the documented `5V` input path

  • 7. BNC shell pins are named `GND` in the connector symbols while intentionally biased above ground

  • Items Verified as Coherent in the Current Schematic

  • Documentation Reverification Findings

  • Firmware Starter - ESP32-C3 pH/ORP ADS1115

  • ESP32-C3 ADS1115 pH/ORP Sensor Validation and Firmware Handoff Report

  • ADS1115 pH Sensor Design Notes

  • ESP32 and Arduino Uno Datasheet Summary

  • Schematic-Level Design Review

  • Recommended Fix Order

ESP32-C3 ADS1115 pH ORP Sensor Interface 4412

ESP32-C3 ADS1115 pH ORP Sensor Interface 4412 thumbnail
ESP32-C3 battery-powered pH and ORP probe interface using ADS1115 differential ADC, MCP6002 through-hole buffers, DS18B20 temperature compensation, and short net labels for firmware handoff.

Properties

Sensor

3.3

V

Arduino

I2C

Battery

Pricing & Availability

Distributor

Qty 1

Arrow

$8.74–$11.13

Digi-Key

$3.68

LCSC

$16.69–$17.39

Mouser

$11.45

TME

$6.21

Verical

$7.55–$15.85

Controls