Meshtastic Sensor Node Schematic
Thought
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 U7
VCC, U7MPPThas a divider, U7COMhas the required RC compensation, and the BAT path now includes a current-sense element between U7BATand the projectBATrail.
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_5Vnet 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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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
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
