This version (18 May 2023 08:50) was approved by Trisha Cabildo.

MAX31865PMB1 RTD-to-digital converter PMOD User Guide

The MAX31865PMB1 peripheral module provides the necessary hardware to interface the MAX31865 RTD-to-digital converter to any system that utilizes Pmod compatible expansion ports configurable for SPI communication. The IC is an easy-to-use resistance-to-digital converter optimized for platinum resistance temperature detectors (RTDs). This module is set up to operate with a PT100 platinum RTD.


Power Supply Requirements

When using the MAX31865 PMOD board, the 3.3 V power comes directly from the host board it is connected to. The power from the host is generally capable of providing up to 100 mA at 3.3 V; but for complete PMOD power specifications, please clickhere.

RTD Connector

Connector CON1 provides connection to the IC pins, as follows:

  • Connector CON1 pin 1 connects to FORCE+ and FORCE2 (pins 5 and 6) of the IC.
  • Connector CON1 pin 2 connects to RTDIN+ (pin 7) of the IC.
  • Connector CON1 pin 3 connects to RTDIN- (pin 8) of the IC.
  • Connector CON1 pin 4 connects to FORCE- (pin 9) of the IC

RTD configuration

Two jumpers at J2 are provided to select either 2-wire or 3-wire RTD configuration. For 2-wire RTD, install both jumpers, from 1-2 and 3-4. For 3-wire RTD, install jumper from 3-4 only.

Digital Interface (PMOD)

The PMOD interface is a series of standardized digital interfaces for various digital communication protocols such as SPI, I2C, and UART. These interface types were standardized by Digilent, which is now a division of National Instruments. Complete details on the PMOD specification can be found here.

The MAX31865PMB1 peripheral module can plug directly into a Pmod-compatible port (configured for SPI) through connector J1. Connector J1 provides a connection of the module to the host. The pin functions and pin assignments adhere to the Pmod standard recommended by Digilent.

Device Driver Support

There are two device driver solutions that are provided for controlling the MAX31865PMB1:

  1. MAX31865 no-OS Driver
    • The MAX31865 no-OS driver is used in bare-metal applications, typically running on low-power, embedded microcontrollers.
  2. MAX31865 Linux Driver
    • The MAX31865 Linux driver is used in applications running the Linux operating system, typically on larger processors and SoC devices.
    • The MAX31865 Linux driver uses the Industrial Input/Output (IIO) framework, greatly simplifying the development of application code via the cross-platform Libiio library, which is written in C and includes bindings for Python, MATLAB, C#, and other languages. Application code can run directly on the platform board, communicating with the device over the local backend, or from a remote host over the network or USB backends.

Schematics, PCB Layout, Bill of Materials

Additional Information


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resources/eval/user-guides/circuits-from-the-lab/max31865pmb1.txt · Last modified: 09 May 2023 07:59 by Trisha Cabildo