IoT Platform PCB & System Design
Budget: ₹1,500 – ₹12,500 INR
FSN-L1 Universal Field Sensor Node — Full Hardware Requirement Specification (v3.4)
Client: Swaroop Dasari / qb³
Revision: v3.4 (Freelancer Handoff Edition)
Purpose: Create the production-grade PCB & system design for the FSN-L1 Universal Sensor Node — a rugged, outdoor, multi-interface, solar-powered IoT platform.
1. Project Vision
FSN-L1 is the flagship universal sensor gateway for the Agriscience & Robotics ecosystem.
Designed for outdoor, agricultural, industrial, research, robotics, drone, and general IoT use cases, FSN-L1 connects any sensor, logs data locally, and transmits over LoRaWAN or Wi-Fi.
The board must be:
Rugged, outdoor-ready
Modular and future-proof
Universal across sectors
Battery + solar powered
Safe, reliable, and secure
Expandable (AI, camera, robotics, etc.)
2. Core Hardware Architecture
Primary Components
MCU: ESP32-S3-WROOM-1
Radio: SX1262 LoRa 868 MHz
Charger: LTC4015 (1S LiFePO₄, MPPT)
Battery: 1S LiFePO₄ (3–20 Ah), with expansion header
Fuel Gauge: MAX17055
RTC: RV-3028 (ultra-low drift)
IMU: BMI270 (6-axis), center-mounted
Storage: microSD (power-gated, 4 KB cluster control)
3. PCB / Mechanical Requirements
4-layer PCB, FR-4, 1.6 mm
Black solder mask, ENIG finish
Max PCB size: 160 × 120 mm
All ports on bottom edge → cables exit horizontally
8 mm edge clearance for enclosure slot
15 mm no-go zone behind connector row (for latch release)
Top edge reserved for LoRa antenna with keep-out
4× M3 mounting holes, 3 mm keep-out radius
Ground plane split A/D with single star join
4. Power System Requirements
4.1 Battery + Solar
1S LiFePO₄ only (3.65 V CV)
3–20 Ah supported
Main battery connector: Phoenix/Amphenol locking 2-pin, ≥10A rated
Expansion battery header allowed (parallel, same voltage)
Reverse polarity protection mandatory
Safety fuse 5A (resettable or fast-blow) on main battery path
Battery NTC for LTC4015 (temperature protection)
4.2 Power Rails
Solar/DC → LTC4015 → Battery
Battery → Load-switch → 5.2 V main bus
5.2 V → Buck → 3.3 V
Boost converter → 6–12 V adjustable for RS-485 / 4–20 mA
Active current limiting on 3.3 V and 5 V rails
Brown-out protection clearly defined
4.3 Deep-Sleep Behavior
All rails OFF
Target draw ≤ 80 µA
microSD rail OFF
Camera/AI rail OFF
5. Sensor Ports (P1–P10 + D1)
All ports must support ESD protection, TVS diodes, ferrite beads, and correct pull-ups.
P1 & P2 — I²C (Level-Shifted)
JST-GH 4-pin (horizontal)
3.3V/5V selectable
PCA9306-based level shifting
Pull-ups: 4.7k
P3 — UART
JST-GH 4-pin
3.3V TTL
Series 100Ω resistors
P4 — RS-485 (Isolated)
M12 A-coded 4-pin
ISO1410 isolation
6–12 V adjustable supply (boost converter)
120Ω termination (solder bridge selectable)
P5 — SDI-12
M8 3-pin
Pull-up 1k–4.7k
P6 — 1-Wire
JST-GH 3-pin
4.7k pull-up
P7a/P7b — Analog (0–3.2V)
3-pin JST-GH
100Ω + 0.1 µF RC filter
Guard traces
P8 — 4–20 mA
Phoenix 2-pin
OPA333 precision amplifier
100Ω shunt
P9 — Pulse / Dry Contact
M8 3-pin
10k pull-up
Debounce RC
P10 — Vision / AI Expansion Port
Connector: JST-GH 8-pin
Voltage: 5V @ 1A fused
Signals:
5V_OUT
GND
UART_TX / UART_RX
VISION_TRIG
VISION_INT
SCL / SDA
Additional Requirements:
CAM_DETECT pin
CAM_EN load switch
TVS for all lines
100µF + 0.1µF local caps
D1 — Display/Debug Port
SPI/I²C display connector
Touch interrupt GPIO
300 mA power budget
Auto-detection recommended
6. Protection Requirements
6.1 Electrical Protection
Surge suppressor (SMBJ/SMCJ) on external ports
ESD protection (USBLC6-2, ESD9x, etc.)
Reverse-polarity MOSFET
Short-circuit detection per rail
Under-voltage lockout
Over-temperature cutoff
EMI filtering (ferrite beads on all sensor ports)
6.2 RF Protection
50Ω microstrip
Ground moat
Antenna clearance ≥ 10 mm
7. microSD Logging Requirements
4KB cluster-aligned writes
Store-forward behavior
Wear-leveling strategy
Power-gated with load-switch
“SD fault” detection LED state
Flush buffer before sleep
8. Buttons & LEDs
Buttons
RESET (to ESP32 RESET)
USER / CONFIG (GPIO)
BOOT/DFU Mode option (GPIO0 or dedicated pad)
LED Indicators
LED Color Meaning
STATUS Green/Red boot, idle, error
COMM Blue/Amber LoRa TX/RX
PWR Red power-good
LED behavior table must be implemented by freelancer.
9. IMU Requirements
BMI270 centered, away from inductors & RF
Guard ring + shielding
INT pin routed to ESP32
Mechanical stability pads
NVS storage for calibration table
10. Firmware-Support Requirements
(Not implemented by freelancer — but hardware must support.)
ESP32 WDT enabled (5–10 sec)
Safe-mode boot logic
Time sync via RTC → NTP fallback
LoRaWAN ADR + retry logic
Port-level fault detection (short, overload)
Camera power control + detect
microSD journal mode
11. Mechanical / Enclosure Requirements
All connectors on bottom edge only
8 mm exit slot
LoRa antenna on top edge
Camera port clustering near D1
External button provision (via harness)
QR label area for serial number
12. Deliverables
The freelancer must submit:
12.1 Hardware Files
Full schematic (KiCad or Altium)
Full PCB layout
4-layer stackup
Gerber, drill, IPC-2581
CPL / Pick-and-place files
3D STEP model
12.2 Documentation
BOM (with alternates)
Assembly notes
Silkscreen labeling
README explaining:
pinouts
placement decisions
fuse ratings
sensor compatibility
power rail behavior
AI/vision port details
13. Success Criteria
For acceptance:
All hardware blocks implemented
All ports protected & labeled
All rails meet current requirements
Deep sleep ≤ 80 µA
microSD + LoRa coexistence validated
IMU interference minimized
Vision port fully functional
Boost converter + isolation verified
DFM clean, no errors
Freelancer provides final renders + documentation
14. Optional (Future-Proofing)
Pads for antenna diversity
Pads for secondary MCU (co-processor)
Room for spectral sensors (AS7341)
MIPI/CSI pads for FSN-L3 variant
USB-C PD input protection option
Client: Swaroop Dasari / qb³
Revision: v3.4 (Freelancer Handoff Edition)
Purpose: Create the production-grade PCB & system design for the FSN-L1 Universal Sensor Node — a rugged, outdoor, multi-interface, solar-powered IoT platform.
1. Project Vision
FSN-L1 is the flagship universal sensor gateway for the Agriscience & Robotics ecosystem.
Designed for outdoor, agricultural, industrial, research, robotics, drone, and general IoT use cases, FSN-L1 connects any sensor, logs data locally, and transmits over LoRaWAN or Wi-Fi.
The board must be:
Rugged, outdoor-ready
Modular and future-proof
Universal across sectors
Battery + solar powered
Safe, reliable, and secure
Expandable (AI, camera, robotics, etc.)
2. Core Hardware Architecture
Primary Components
MCU: ESP32-S3-WROOM-1
Radio: SX1262 LoRa 868 MHz
Charger: LTC4015 (1S LiFePO₄, MPPT)
Battery: 1S LiFePO₄ (3–20 Ah), with expansion header
Fuel Gauge: MAX17055
RTC: RV-3028 (ultra-low drift)
IMU: BMI270 (6-axis), center-mounted
Storage: microSD (power-gated, 4 KB cluster control)
3. PCB / Mechanical Requirements
4-layer PCB, FR-4, 1.6 mm
Black solder mask, ENIG finish
Max PCB size: 160 × 120 mm
All ports on bottom edge → cables exit horizontally
8 mm edge clearance for enclosure slot
15 mm no-go zone behind connector row (for latch release)
Top edge reserved for LoRa antenna with keep-out
4× M3 mounting holes, 3 mm keep-out radius
Ground plane split A/D with single star join
4. Power System Requirements
4.1 Battery + Solar
1S LiFePO₄ only (3.65 V CV)
3–20 Ah supported
Main battery connector: Phoenix/Amphenol locking 2-pin, ≥10A rated
Expansion battery header allowed (parallel, same voltage)
Reverse polarity protection mandatory
Safety fuse 5A (resettable or fast-blow) on main battery path
Battery NTC for LTC4015 (temperature protection)
4.2 Power Rails
Solar/DC → LTC4015 → Battery
Battery → Load-switch → 5.2 V main bus
5.2 V → Buck → 3.3 V
Boost converter → 6–12 V adjustable for RS-485 / 4–20 mA
Active current limiting on 3.3 V and 5 V rails
Brown-out protection clearly defined
4.3 Deep-Sleep Behavior
All rails OFF
Target draw ≤ 80 µA
microSD rail OFF
Camera/AI rail OFF
5. Sensor Ports (P1–P10 + D1)
All ports must support ESD protection, TVS diodes, ferrite beads, and correct pull-ups.
P1 & P2 — I²C (Level-Shifted)
JST-GH 4-pin (horizontal)
3.3V/5V selectable
PCA9306-based level shifting
Pull-ups: 4.7k
P3 — UART
JST-GH 4-pin
3.3V TTL
Series 100Ω resistors
P4 — RS-485 (Isolated)
M12 A-coded 4-pin
ISO1410 isolation
6–12 V adjustable supply (boost converter)
120Ω termination (solder bridge selectable)
P5 — SDI-12
M8 3-pin
Pull-up 1k–4.7k
P6 — 1-Wire
JST-GH 3-pin
4.7k pull-up
P7a/P7b — Analog (0–3.2V)
3-pin JST-GH
100Ω + 0.1 µF RC filter
Guard traces
P8 — 4–20 mA
Phoenix 2-pin
OPA333 precision amplifier
100Ω shunt
P9 — Pulse / Dry Contact
M8 3-pin
10k pull-up
Debounce RC
P10 — Vision / AI Expansion Port
Connector: JST-GH 8-pin
Voltage: 5V @ 1A fused
Signals:
5V_OUT
GND
UART_TX / UART_RX
VISION_TRIG
VISION_INT
SCL / SDA
Additional Requirements:
CAM_DETECT pin
CAM_EN load switch
TVS for all lines
100µF + 0.1µF local caps
D1 — Display/Debug Port
SPI/I²C display connector
Touch interrupt GPIO
300 mA power budget
Auto-detection recommended
6. Protection Requirements
6.1 Electrical Protection
Surge suppressor (SMBJ/SMCJ) on external ports
ESD protection (USBLC6-2, ESD9x, etc.)
Reverse-polarity MOSFET
Short-circuit detection per rail
Under-voltage lockout
Over-temperature cutoff
EMI filtering (ferrite beads on all sensor ports)
6.2 RF Protection
50Ω microstrip
Ground moat
Antenna clearance ≥ 10 mm
7. microSD Logging Requirements
4KB cluster-aligned writes
Store-forward behavior
Wear-leveling strategy
Power-gated with load-switch
“SD fault” detection LED state
Flush buffer before sleep
8. Buttons & LEDs
Buttons
RESET (to ESP32 RESET)
USER / CONFIG (GPIO)
BOOT/DFU Mode option (GPIO0 or dedicated pad)
LED Indicators
LED Color Meaning
STATUS Green/Red boot, idle, error
COMM Blue/Amber LoRa TX/RX
PWR Red power-good
LED behavior table must be implemented by freelancer.
9. IMU Requirements
BMI270 centered, away from inductors & RF
Guard ring + shielding
INT pin routed to ESP32
Mechanical stability pads
NVS storage for calibration table
10. Firmware-Support Requirements
(Not implemented by freelancer — but hardware must support.)
ESP32 WDT enabled (5–10 sec)
Safe-mode boot logic
Time sync via RTC → NTP fallback
LoRaWAN ADR + retry logic
Port-level fault detection (short, overload)
Camera power control + detect
microSD journal mode
11. Mechanical / Enclosure Requirements
All connectors on bottom edge only
8 mm exit slot
LoRa antenna on top edge
Camera port clustering near D1
External button provision (via harness)
QR label area for serial number
12. Deliverables
The freelancer must submit:
12.1 Hardware Files
Full schematic (KiCad or Altium)
Full PCB layout
4-layer stackup
Gerber, drill, IPC-2581
CPL / Pick-and-place files
3D STEP model
12.2 Documentation
BOM (with alternates)
Assembly notes
Silkscreen labeling
README explaining:
pinouts
placement decisions
fuse ratings
sensor compatibility
power rail behavior
AI/vision port details
13. Success Criteria
For acceptance:
All hardware blocks implemented
All ports protected & labeled
All rails meet current requirements
Deep sleep ≤ 80 µA
microSD + LoRa coexistence validated
IMU interference minimized
Vision port fully functional
Boost converter + isolation verified
DFM clean, no errors
Freelancer provides final renders + documentation
14. Optional (Future-Proofing)
Pads for antenna diversity
Pads for secondary MCU (co-processor)
Room for spectral sensors (AS7341)
MIPI/CSI pads for FSN-L3 variant
USB-C PD input protection option