Adafruit MAX31865 RTD Amplifier Breakout

SPI resistance-to-digital converter breakout supporting 2-, 3-, and 4-wire PT100 and PT1000 RTDs. Reference resistor is 430 Ω (PT100) or 4300 Ω (PT1000). Supply: 3.3 V or 5 V.

Logical pinout · physical placement not verified

VIN
Supply voltage — 3.3 V or 5 V; Adafruit breakout has onboard 3.3 V LDO
Type · PowerVoltage · 3.3
GND
Ground reference
Type · Ground
SCK
SPI clock from ESP32-S3
Type · SPI
SDI
SPI MOSI — data in to MAX31865
Type · SPI
SDO
SPI MISO — data out from MAX31865
Type · SPI
CS
SPI chip-select (active low); assign a free GPIO on ESP32-S3, avoid flash/JTAG pins
Type · SPI
DRDY
Data-ready interrupt output — optional; can poll instead
Type · Signal
F+
RTD force positive (connect to one RTD lead / Pt probe terminal)
Type · Signal
F-
RTD force negative (connect to other RTD lead / Pt probe terminal)
Type · Signal
RTD+
RTD sense positive (2-wire: jumper to F+; 4-wire: separate sense lead)
Type · Signal
RTD-
RTD sense negative (2-wire: jumper to F-; 4-wire: separate sense lead)
Type · Signal

Pin	Type	Function	Voltage
VIN	Power	Supply voltage — 3.3 V or 5 V; Adafruit breakout has onboard 3.3 V LDO	3.3
GND	Ground	Ground reference
SCK	SPI	SPI clock from ESP32-S3
SDI	SPI	SPI MOSI — data in to MAX31865
SDO	SPI	SPI MISO — data out from MAX31865
CS	SPI	SPI chip-select (active low); assign a free GPIO on ESP32-S3, avoid flash/JTAG pins
DRDY	Signal	Data-ready interrupt output — optional; can poll instead
F+	Signal	RTD force positive (connect to one RTD lead / Pt probe terminal)
F-	Signal	RTD force negative (connect to other RTD lead / Pt probe terminal)
RTD+	Signal	RTD sense positive (2-wire: jumper to F+; 4-wire: separate sense lead)
RTD-	Signal	RTD sense negative (2-wire: jumper to F-; 4-wire: separate sense lead)

Logical pinout · physical placement not verified

Pin details

11 connections

VIN
Supply voltage — 3.3 V or 5 V; Adafruit breakout has onboard 3.3 V LDO
PowerVoltage · 3.3
GND
Ground reference
Ground
SCK
SPI clock from ESP32-S3
SPI
SDI
SPI MOSI — data in to MAX31865
SPI
SDO
SPI MISO — data out from MAX31865
SPI
CS
SPI chip-select (active low); assign a free GPIO on ESP32-S3, avoid flash/JTAG pins
SPI
DRDY
Data-ready interrupt output — optional; can poll instead
Signal
F+
RTD force positive (connect to one RTD lead / Pt probe terminal)
Signal
F-
RTD force negative (connect to other RTD lead / Pt probe terminal)
Signal
RTD+
RTD sense positive (2-wire: jumper to F+; 4-wire: separate sense lead)
Signal
RTD-
RTD sense negative (2-wire: jumper to F-; 4-wire: separate sense lead)
Signal

Start wiring

I2C · SPI · Single data line · 3.3 – 5 V · Breakout

Verify supply voltage and logic levels before powering up.

Module pins: VIN, GND, SCK, SDI, SDO, CS. Schematik maps them to your board in the app.

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