• Outdoor livestock collar electronics module exposed to rain, mud, snow, dust, vibration, and impact.
• Temperature target: -40C to +50C.
• Not a bench development board; design should include production-style protection, test access, isolation, and keepouts.

• Run main control firmware on ESP32-S3-WROOM-1-N16R8.
• Communicate via 915 MHz LoRa using an SX1262 transceiver and external U.FL antenna.
• Receive GNSS position data from a u-blox MAX-M10S module with external U.FL antenna.
• Read motion from BMA400 accelerometer over I2C.
• Read ambient/local temperature from TMP117 over I2C.
• Capture audio using ICS-43434 I2S MEMS microphone.
• Drive one off-board vibration motor and one off-board waterproof piezo buzzer through low-side MOSFET drivers.
• Provide local 2 x 32700 LiFePO4 cell solder-tab/holder pads tied to the shared 1S pack bus.
• Pass solar panel A input through to an external power board; this board does not charge the battery.
• Carry an isolated high-voltage electrode pad from an external stimulation board; this board does not generate high voltage.

• ESP32-S3 MCU with EN/reset, IO0 boot/programming, UART debug/programming header, and test points.
• SX1262 LoRa RF section with 915 MHz matching/pi tuning footprint, RF ESD, U.FL, and antenna keepout.
• MAX-M10S GNSS section with filtered 3V3 supply, backup supply footprint if supported, RF ESD, U.FL, and antenna keepout.
• I2C sensor bus with pull-ups and sensor interrupt nets.
• I2S MEMS microphone with acoustic port keepout and port marker.
• Local actuator drivers with gate resistors, pulldowns, transient protection, and test points.
• Soldered flex-tail landing area with four physical zones: low-voltage signal, high-current battery, solar pass-through, and isolated HV electrode.
• Extensive labeled test points.

Diagram

• Required nets: CELL_PACK_PLUS, PACK_GND, 3V3.
• 3V3 is received already regulated from external power board through soldered flex tail.
• No charger, BMS, 3V3 regulator, or stimulation generator on this PCB.
• Bulk capacitance near flex tail 3V3 input.
• 0.1uF decoupling near every IC.
• 10uF or larger near ESP32, SX1262, and GNSS.
• Battery and solar voltage sense dividers to ESP32 ADC with protection/clamp as needed.

• ESP32-S3-WROOM-1-N16R8 main MCU.
• EN/reset RC circuit and reset access.
• IO0 boot/programming circuit.
• UART programming/debug header.
• Test points: ESP_EN, ESP_IO0, UART_TX, UART_RX, 3V3, GND.

• SX1262 LoRa on SPI with LoRa control pins.
• 915 MHz matching network and pi-network tuning footprint.
• U.FL antenna connectors and ESD protection.
• MAX-M10S GNSS on UART with clean filtered 3V3 supply and optional backup supply footprint if supported.
• RF and GNSS sections near outside board edge with antenna keepouts and no copper under keepouts.

• BMA400 I2C accelerometer: I2C_SCL, I2C_SDA, IMU_INT1, IMU_INT2.
• TMP117 I2C temperature sensor: I2C_SCL, I2C_SDA; place away from heat sources.
• ICS-43434 I2S MEMS microphone: MIC_BCLK, MIC_WS, MIC_SD; place away from motor, buzzer, high-current pads, switching noise, and vibration sources.

• Vibration motor A on connector/pads J_VIB_A with N-channel low-side MOSFET, gate resistor, gate pulldown, flyback/transient protection, and test points VIB_A_PWM and VIB_A_OUT.
• Waterproof piezo buzzer A on connector/pads J_BUZZ_A with N-channel low-side MOSFET, gate resistor, gate pulldown, transient protection if needed, and test points BUZZ_A_PWM and BUZZ_A_OUT.

• J_ELECTRODE_A isolated pad/connector on ELECTRODE_A_HV.
• HV arrives from external stimulation board through soldered flex tail.
• Keep ELECTRODE_A_HV isolated from RF, GNSS, microphone, 3V3, I2C, SPI, and UART.
• Add copper keepout and silkscreen warning around electrode route.

• LoRa SPI/control nets: LORA_SCK, LORA_MOSI, LORA_MISO, LORA_NSS, LORA_RESET, LORA_BUSY, LORA_DIO1.
• GNSS UART nets: GNSS_TX, GNSS_RX.
• I2C nets: I2C_SCL, I2C_SDA.
• Sensor/actuator nets: IMU_INT1, IMU_INT2, MIC_BCLK, MIC_WS, MIC_SD, VIB_A_PWM, BUZZ_A_PWM.
• Power/sense nets: CELL_PACK_PLUS, PACK_GND, 3V3, BAT_SENSE_A, SOLAR_A_PLUS, SOLAR_A_SENSE.
• Flex-tail low-voltage Zone 1 pinout: GND, GND, 3V3, 3V3, I2C_SCL, I2C_SDA, ACTUATOR_B_VIB_PWM, ACTUATOR_B_BUZZ_PWM, SHOCK_ENABLE, SHOCK_PULSE, SHOCK_FAULT, CHG_STAT1, CHG_STAT2, BAT_TEMP_B, BAT_SENSE_B, SOLAR_A_SENSE, SPARE_GPIO1, SPARE_GPIO2, SPARE_GPIO3, GND.
• Flex-tail Zone 2: at least two CELL_PACK_PLUS pads and two PACK_GND pads rated for at least 5A margin.
• Flex-tail Zone 3: SOLAR_A_PLUS pass-through pad; solar return uses PACK_GND.
• Flex-tail Zone 4: isolated ELECTRODE_A_HV pad.

• External board provides regulated 3V3.
• Local cells are LiFePO4 32700, final pack configuration 4P1S, with local two cells tied to shared 1S pack bus.
• Solar panel A: 6V nominal, 1W, approximately 110 mm x 60 mm; this board only passes solar input through.
• Runtime target not specified yet.

• 4-layer rigid FR4 PCB.
• Stackup target: L1 signal/components, L2 solid GND plane, L3 power routing, L4 signal.
• Target assembly through JLCPCB/LCSC where practical.
• Exposed soldered flex-tail landing area instead of FPC/ZIF connector.
• Production prototype: include fiducials/alignment marks, test points, protection, keepouts, and silkscreen warnings.

• ESP32-S3 pin assignment must support LoRa SPI, GNSS UART, I2C sensors, I2S microphone, PWM actuator outputs, ADC battery/solar sensing, and flex-tail external control/status nets.
• Boot and reset access required through IO0 and EN.
• UART programming/debug header required.
• Firmware starter file will be generated after schematic pin assignments are finalized.

• Board target size: 120 mm x 80 mm.
• RF and GNSS near outside board edge.
• Antennas clear of battery cells and flex tail.
• Microphone away from vibration motor, buzzer, high-current pads, and switching noise.
• TMP117 away from heat sources.
• Electrode route isolated with copper keepout and HV warning.
• No autorouting until placement is approved.

• Use module-based ESP32-S3 to avoid custom WiFi/BLE RF design.
• Use external U.FL antennas for LoRa and GNSS.
• Keep charging, BMS, 3V3 regulation, and stimulation generation off-board per user request.
• Use a 4-layer stackup with solid L2 ground plane for RF return paths and signal integrity.

• SMD assembly is preferred because this is a production-prototype board and JLCPCB/LCSC assembly is targeted.
• External power board can supply sufficient 3V3 peak current for ESP32-S3 WiFi/BLE plus SX1262 transmit and GNSS operation.
• Flex-tail pads and battery solder pads may require custom footprint/layout nodes if exact mechanical drawing is not available.
• Exact RF matching values may need tuning with VNA measurements; schematic will include pi-network footprints and nominal reference values from datasheets/reference designs where available.

• Initial specification created from the user request.