Meshtastic Sensor Node Schematic

flux

  • Connected J1:VBUS_A, J1:VBUS_B, U7:VCC, C17:P1, C18:P1, C22:P1, C23:P1 to ^SOLAR_IN
  • Connected U7:MPPT, R8:P1, R9:P2 to ^MPPT_SET
  • Connected R8:P2, J1:VBUS_A, J1:VBUS_B, U7:VCC, C17:P1, C18:P1, C22:P1, C23:P1 to ^Net 1
  • Connected R9:P1, C26:P2, C25:P2 to ^GND
  • Connected U7:COM, R7:P1 to ^CHG_COMP
  • Connected R7:P2, C26:P1 to ^Net 2
  • Connected U7:BAT, R10:P1 to ^BAT_CHG
  • Connected U7:CSP, R10:P2, SW1:1, J2:1, C24:P1, C25:P1 to ^BAT
  • Connected SW1:2, U6:VIN, C19:P1 to ^VSYS
  • Disconnected U7:BAT, SW1:1, J2:1, C24:P1
nets {
net 3V3 = R15:P1, C20:P1, C7:P1, R2:P1, C5:P1, C3:P1, C4:P1, C13:P1, U6:CE, R4:P1, R3:P1, R12:P1, C14:P1, U2:VBAT_IO, U2:VBAT, U1:VDD_SPI, U1:VDDA2, U1:VDDA1, U1:VDD3P3_RTC, U1:VDD3P3_CPU, U1:3, U1:2, U2:VDD_IN, C11:P1, C6:P1, R11:P1, R16:P1, U6:VOUT, C8:P1, C2:P1, C12:P1, R1:P1;
net GND = X2:2, X1 GND - X1 GND:GND, R9 P1 - C26 P2:GND, C25:P2, C26:P2, R9:P1, U4 GND - U5 GND:GND, C3:P2, R13 P2 - R14 P2:GND, C17:P2, C15:P2, U7:GND, C1:P2, C2:P2, J1:GND_A, C6:P2, D1:A, C14:P2, R13:P2, GND:GND, U2:GND_1, U2:GND_2, C4:P2, U2 GND_5 - U3 GND:GND, R14:P2, C9:P2, Q1:S, C13:P2, U2:GND_5, U2:GND_4, X1:2, C18:P2, X1:4, C12:P2, Q2:S, U2 GND_2 - U2 GND_3:GND, J2:2, LED2:K, R5:P2, C19:P2, U5:GND, U3 GND - U4 GND:GND, C20:P2, J1:GND_B, U2:GND_3, C21:P2, C7:P2, C11:P2, X2:4, R6:P2, C10:P2, C24:P2, U1:GND, C5:P2, U6:GND, C16:P2, LED1:K;
net USB_CC2 = J1:CC2, R14:P1;
net VBUS_5V = U5:VCC, D1:2, D1:1, R8:P2, C23:P1, C22:P1, C18:P1, C17:P1, U7:VCC, J1:VBUS_B, J1:VBUS_A;
net DONE = R12:P2, U7:~DONE;
net USB_CC1 = J1:CC1, R13:P1;
net CHRG = U7:~CHRG, R11:P2;
net MPPT_SET = U7:MPPT, R9:P2, R8:P1;
net CHG_COMP = U7:COM, R7:P1;
net Net 2 = R7:P2, C26:P1;
net BAT_CHG = U7:BAT, R10:P1;
net BAT = U7:CSP, C25:P1, C24:P1, J2:1, SW1:1, R10:P2;
net VSYS = SW1:2, C19:P1, U6:VIN;
}

flux

Work done
  • Audited the existing U7 charger block against datasheet guidance and identified the missing support elements: input bypassing, COM compensation, MPPT divider, and BAT-path current sense/filtering.
  • Added new support parts around U7: C22, C23, C25, C26, R7, R8, R9, and R10.
  • Wired the new network so the solar/input side is bypassed at U7VCC, U7MPPT has a divider, U7COM has the required RC compensation, and the BAT path now includes a current-sense element between U7BAT and the project BAT rail.
Success criteria review
  • ✅ The missing passive support network was substantially added around U7.
  • ✅ BAT, VSYS, and the charger-related nets now have explicit connectivity reflecting the intended power path.
  • ❌ I could not finish verification and documentation because execution is blocked in this session before I can perform the final schematic review pass and update the project document.
  • ❌ One net naming cleanup is still needed: the input rail write reused the existing VBUS_5V net instead of creating a distinct solar-specific label, so I could not complete the requested net-label cleanup/documentation step.
Next steps
The charger support components are now in place, but the project still needs one cleanup pass to rename the input rail appropriately, run a targeted review on the U7 section, and update Project Specification. Once execution is available again, I can finish those remaining steps.
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Schematic

Layout

Preview

U1
Manufacturer Part Number
ESP32-S3FN8
U7
C14
Capacitance
10uF
C4
Capacitance
100nF
C5
Capacitance
100nF
C1
Capacitance
100nF
C24
Capacitance
10uF
C23
Capacitance
100nF
R1
Resistance
10kΩ
C11
Capacitance
100nF
C12
Capacitance
100nF
C20
Capacitance
10uF
C17
Capacitance
10uF
R5
Resistance
10kΩ
R15
Resistance
330 Ω
R7
Resistance
120Ω
C25
Capacitance
4.7uF
R16
Resistance
330 Ω
R14
Resistance
5.1kΩ
C16
Capacitance
12pF
C19
Capacitance
10uF
R12
Resistance
10kΩ
R6
Resistance
10kΩ
C21
Capacitance
100nF
C8
Capacitance
10uF
C15
Capacitance
12pF
R8
Resistance
178kΩ
C7
Capacitance
100nF
C9
Capacitance
12pF
R2
Resistance
10kΩ
C26
Capacitance
220nF
C3
Capacitance
100nF
C2
Capacitance
100nF
R10
Resistance
100mΩ
C18
Capacitance
100nF
R13
Resistance
5.1kΩ
R11
Resistance
10kΩ
R3
Resistance
10kΩ
C6
Capacitance
100nF
C10
Capacitance
12pF
R4
Resistance
10kΩ
R9
Resistance
22kΩ
C13
Capacitance
100nF
C22
Capacitance
4.7uF
X2
LED1
L1
Inductance
3.9nH
J1
X1
LED2
D1
U6
U5
J2
SW1
Q2
J3
Q1
U2
Manufacturer Part Number
SX1262IMLTRT
Project Specification
Overview
A Meshtastic-compatible solar-powered sensor node built around an ESP32-S3FN8 MCU and SX1262 LoRa transceiver. The design includes LiPo battery support, solar charging, 3.3 V regulation, USB-UART flashing with auto-reset, external sensor inputs, status LEDs, and an RF path to an SMA antenna connector.
Architecture
Diagram



  
    
  
  
    
  































USB-C node_5V Input
LiPo Charger
Solar Input
LiPo Battery
Battery Switch
3.3V LDO
ESP32-S3 MCU
SX1262 LoRa Radio
Sensor Interfaces
USB-UART Bridge
Auto Reset MOSFETs
RF Matching Network
SMA Antenna
Status LEDs
Functional Blocks
  • ESP32-S3FN8 MCU with external 40 MHz crystal, boot/reset support, and decoupling.
  • USB-UART programming interface with automatic boot and reset control.
  • SX1262 LoRa transceiver with crystal, RF matching/filter network, and SMA connector.
  • Analog sensor inputs for MQ-2 smoke sensing and rain sensing with ADC-safe scaling.
  • Solar/LiPo charging subsystem and battery-powered 3.3 V rail.
  • Status indication LEDs for power and MCU activity.
Design Decisions
  • Use USB-UART instead of native USB so the flashing interface remains explicit and compatible with standard ESP32 auto-reset behavior.
  • Use a simple LiPo charger plus solar input path to satisfy the requested solar charging requirement.
  • Use an LDO for 3.3 V generation because the node is battery powered from a single-cell LiPo and low noise is preferred for RF and ADC sections.
  • Keep external sensor inputs on headers so MQ-2 and rain sensor modules can be attached without forcing a specific transducer footprint.
Intended Nets
  • Power: 3V3, GND, VBUS_5V, BAT, VSYS, SOLAR_IN
  • ESP32 programming/control: U0TXD, U0RXD, EN, BOOT, DTR, RTS
  • LoRa: LORA_SCK, LORA_MOSI, LORA_MISO, LORA_NSS, LORA_BUSY, LORA_DIO1, LORA_NRST
  • Sensors: MQ2_AO, MQ2_DO, RAIN_AO
  • Status: LED_PWR, LED_STATUS
Notes
This specification records the intended architecture before schematic completion. Exact GPIO assignments and part substitutions may be refined during implementation based on library availability and pin compatibility.

  • Overview

  • Architecture

  • Functional Blocks

  • Design Decisions

  • Intended Nets

  • Notes