Reading notes from researching hardware for a vehicle-telemetry style project. The product is private, so this keeps to the parts, interfaces and trade-offs, which apply to any IoT or edge build. Most of it is research, not hands-on; the hands-on hardware is the Pi (Raspberry Pi and Single-Board Computers). How to choose and stage a build: Prototyping Hardware - Bench to Field.
The signal chain
flowchart LR
S[Sensors and buses: CAN, GNSS, load, fuel, ID tags] --> E[Edge compute: Pi / MCU / gateway]
E --> M[Modem: LTE / Wi-Fi / satellite]
M --> C[Cloud broker over TLS: MQTT / HTTP]
C --> A[Storage, analytics, dashboards]
Edge Compute
| Option | Strength | Limitation | Best use |
|---|---|---|---|
| Raspberry Pi 5 | Real Linux, containers, Python, huge community | Not automotive-qualified | Main bench computer |
| Raspberry Pi Compute Module 5 + I/O board | Closer to an embedded product | Needs a properly engineered carrier, power, certification | Second bench iteration, enclosure mock-up |
| Arduino Portenta H7 | Real-time MCU work, industrial I/O | Less convenient than Linux for a full app | Deterministic input node |
| ESP32-S3 dev board | Cheap, Wi-Fi and BLE | Dev board only | Many fake BLE sensors and tags |
| Industrial fanless PC | Robust Linux, SSD, expansion | Cost and power | Load testing, site gateway |
CAN Bus and J1939
CAN is the robust two-wire bus used inside vehicles and industrial machines. J1939 is the higher-level protocol used on heavy vehicles and engines (standard rate 250 kbit/s on a 29-bit-ID CAN), defining parameter group numbers (PGNs) and suspect parameter numbers (SPNs) for readings like engine speed or coolant temperature.
| Adapter | Type | Notes |
|---|---|---|
| Kvaser Leaf Light HS v2 (J1939 connector version) | Professional USB-CAN | Good for heavy-vehicle connectors |
| PEAK PCAN-USB FD | Professional USB CAN / CAN FD | Mature tools and API; CAN FD ready |
| CSS Electronics CANedge2 | CAN data logger with Wi-Fi | Logging, DBC decoding workflows |
| CSS Electronics CANmod.input | Analogue / digital / pulse to CAN | Represent bench sensors on CAN without a custom board |
| CANable-style hobby adapters | Low-cost USB-CAN | Fine for early software tests; do not make it the reference |
| SPI CAN HAT on a Pi (MCP2515) | Cheap native CAN | Good for learning with SocketCAN |
Working rules:
- Listen-only mode when connected to anything real, so you cannot disturb the bus
- Generate test frames on an isolated bench bus, never onto a working vehicle
- Decode with a DBC file and tools such as can-utils, python-can, cantools
$ sudo ip link set can0 up type can bitrate 250000
$ candump can0
$ cansend can0 18FEF100#FFFFFFFFFFFFFFFF
Positioning (GNSS)
| Family | Capability | Use |
|---|---|---|
| u-blox ZED-F9R | Dual-band, with dead reckoning | Best accuracy reference |
| u-blox NEO-M9N | Multi-constellation standard precision | Low-cost live-location bench option |
| u-blox M10 modules | Modern, low power | Simple position source |
| Basic USB GNSS puck | NMEA text stream | Cheapest, when accuracy is not under test |
Software should keep fix type, satellite count, accuracy estimates and timestamp quality, not just latitude and longitude. A production device normally uses the GNSS built into its gateway; separate modules are an independent reference to judge it.
Connectivity
| Option | Use | Caution |
|---|---|---|
| Industrial LTE router (Teltonika RUT-class) | Easy Internet for a bench computer | Not the in-vehicle gateway |
| LTE HATs for Pi (Sixfab kits) | Direct modem experiments | Check the bands for your country, approvals and drivers |
| Cellular modules (Quectel EG25-G LTE Cat 4, SIMCom A7672 Cat 1) | Module-level learning | Integration and certification are separate work |
| Smartphone hotspot | Quickest test | Not repeatable |
| Satellite (Iridium short-burst data modems, integrated cellular + satellite trackers) | Where there is no coverage | Needs its own antenna and costs more per message |
| LoRa / LoRaWAN | Long range, tiny payloads | Different network and data rates |
Cellular categories in brief: LTE Cat 1 / Cat 1bis (moderate data, widely supported), Cat M1 / NB-IoT (very low power, small payloads, coverage varies), Cat 4 (higher speed). Check coverage and mobility on the actual routes, not just maps.
Sensing
| Measurement | Bench parts | Field parts and notes |
|---|---|---|
| Weight / payload | Small bar load cell with HX711 amplifier; four-corner platform | Onboard air-suspension scales and industrial Modbus / RS-485 transmitters; readings are estimates needing empty and loaded calibration and comparison with a weighbridge |
| Fuel / liquid level | Water container with ultrasonic or low-voltage level sensor; simulated values | Capacitive tank sensors (digital RS-232 / RS-485, CAN or BLE variants); installation by qualified fitters; the ECU's own fuel value is a baseline but often too coarse |
| Driver / asset ID | PN532 NFC board, USB RFID reader, iButton reader, BLE tags | iButton and RFID are common in commercial trackers; consider cloning risk and enrolment |
| Environment | BME280 (temperature, humidity, pressure), DS18B20 probe | Probes sealed for field use |
| Motion / orientation | IMU: BNO085, ICM-20948 | Harsh-braking and impact detection; do not duplicate if the gateway already provides it |
| Tamper / buttons | Reed switch, push button | Enclosure-open and panic inputs |
| Analogue signal simulation | Rotary potentiometer | Fake an analogue fuel or load signal |
Interfaces you will meet: I2C and SPI (short-range chip buses), UART / RS-232 / RS-485 (serial; RS-485 is differential and runs long cables), Modbus (simple industrial protocol over RS-485 or TCP), 1-Wire, analogue 0-5 V / 4-20 mA, BLE, CAN.
Sensor data is noisy: filter it (median or moving average), calibrate it, store raw and processed values, and keep units and timestamps explicit.
Gateways (Buy Instead of Build)
A telematics gateway collapses several bench devices (GNSS, LTE, CAN, serial I/O, backup battery, certificates) into one certified box.
| Family | Notes |
|---|---|
| Teltonika FMC650 / FMM650 | Professional trackers with CAN and external antennas; LTE Cat 1 and LTE-M variants |
| Digital Matter G150 Global | Cat 1bis, IP68, rich I/O, RS-232, BLE, wide voltage input, optional satellite |
| Ruptela Trace5, Queclink GV350 series | Established vehicle tracker families |
| Linux vehicle computers (Advantech, AAEON, OnLogic class) | Containers and local analytics; higher power and cost |
Do not rely on a marketing page: ask for the datasheet, test on the bench, then test on the intended vehicle class. A weighted scoring method is in Prototyping Hardware - Bench to Field.
Antennas, Enclosures and Connectors
- Antennas: combined LTE + GNSS (+ Wi-Fi) automotive antennas from vendors such as Taoglas, Panorama, PCTEL and 2J. Match connector type, cable loss, bands, mounting surface and ingress rating to the modem; choose antennas after the modem. Satellite needs its own approved antenna
- Enclosures: Hammond, Polycase, Fibox and ROLEC IP-rated boxes; certified cable glands and strain relief
- Automotive connectors: Deutsch DT / DTM, TE AMPSEAL, Amphenol sealed connectors; harness design follows the gateway and installer requirements
- IP ratings: the first digit is dust, the second water (IP67 survives temporary immersion; IP68 continuous immersion to a stated depth)
Prototyping Fabrication
| Option | Use |
|---|---|
| Off-the-shelf ABS or polycarbonate project box | First bench build |
| PETG / ASA FDM print | Fast fit and mounting iterations; ASA tolerates UV and heat better |
| PA12 nylon (SLS / MJF) | Stronger presentation part with fine detail |
| Transparent acrylic | Demo where components should stay visible |
3D printing proves fit and appearance, not fire resistance, EMC, water ingress, vibration or automotive suitability.