The same measurand may ship as analog voltage, 4–20 mA, UART Modbus, or I2C registers. Interface choice drives BOM, EMC, maintenance, and firmware complexity. Senseiot modules span digital and analog outputs—this guide helps pick manufacturable, scalable interfaces early.
Analog Voltage (0–5 V / 0–10 V)
Easy for MCU ADC on short cables (<3 m) but suffers IR drop and EMI on long runs—use shielding and single-point ground.
Match output impedance; add buffers; ratiometric designs cancel supply drift.
PLC cards accept 0–10 V but current loops beat voltage in noisy plants—see Product Catalog analog modules.
4–20 mA Current Loops
Two-wire loops resist line impedance changes and EMI—process industry default. 0 mA signals wire break.
Mind loop voltage budget and IS barriers on multi-drop loops.
Senseiot transmitters digitize sensor cores to 4–20 mA for legacy SCADA—Industry Applications.
I2C and SMBus
Two-wire bus for PCB-level MEMS, RH, light sensors—100/400 kHz, short traces (<30 cm).
Capacitance limits length and device count—extenders or RS485 for field runs; pull-ups and level shifters required.
Gas/IAQ modules expose cal registers over I2C—Product Catalog.
UART and RS485 Modbus
Modbus RTU over UART/RS485 to 1200 m with multi-drop addressing—registers for concentration, T, RH, status.
Mature PLC/gateway ecosystem—plan addresses and termination.
TCP Modbus over IP on Senseiot gateways—Request a Quote for mapping.
SPI and High-Speed Digital
Four-wire SPI at MHz rates for IMU burst reads—on-board only, not long cables.
Remote nodes aggregate on MCU then UART uplink for kHz needs.
SPI sensor + RS485 aggregator common in Industry Application vibration nodes.
Selection Matrix
PCB multi-sensor low power → I2C; field PLC → RS485 or 4–20 mA; legacy DCS → 4–20 mA/HART; onboard speed → SPI.
Score cable length, EMI, controller IO, diagnostics needs.
Never stretch I2C tens of meters—use transmitter boxes.
Integration and Debug Tips
Decouple power, add ESD, IP-rated connectors; digital links need comms-loss fail-safe.
Bring-up: power → idle → registers → dynamic stimulus → drift log.
Senseiot multi-interface modules and SDK—Request a Quote.