MAX31855 no-OS Example Project

See projects/max31855 (doxygen) for the Doxygen documentation.

Supported Evaluation Boards

Overview

The MAX31855PMB peripheral module provides the necessary hardware to interface the MAX31855 cold-junction compensated thermocouple-to-digital converter to any system that utilizes Pmod-compatible expansion ports. The MAX31855 performs cold-junction compensation and digitizes the signal from a thermocouple. Versions of it are available that operate with a K-, J-, N-, T-, S-, R-, or E-type thermocouple.

This module is set up to operate with a K-type thermocouple. The data is output in a signed 14-bit, SPI-compatible, read-only format. This converter resolves temperatures to 0.25 degrees C, allows readings as high as +1800 degrees C and as low as -270 degrees C, and exhibits thermocouple accuracy of +/-2 degrees C for temperatures ranging from -200 degrees C to +700 degrees C for K-type thermocouples.

Applications

  • Appliances

  • Automotive

  • HVAC

  • Industrial

Hardware Specifications

Power Supply Requirements

When using the MAX31855 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.

Board Connectors

The MAX31855PMB1 peripheral module can plug directly into a Pmod-compatible port (configured for SPI) through connector J1.

Pin

Signal

Description

1

SS

Chip enable (active low)

2

N.C.

Not connected

3

MISO

Serial data output

4

SCK

Serial clock input

5

GND

Ground

6

VCC

Power supply

No-OS Build Setup

Please see: No-OS Build Guide

No-OS Supported Examples

The initialization data used in the examples is taken out from the Project Common Data Path.

The macros used in Common Data are defined in platform-specific files found in the Project Platform Configuration Path.

Basic Example

The basic example initializes the MAX31855 thermocouple-to-digital converter, reads thermocouple and ambient temperature data in a loop, prints the results to the console, and updates readings every two seconds. If initialization or data reading fails, it logs an error and cleans up resources.

In order to build the basic example, make sure you have the following configuration in the Makefile:

# Select the example you want to enable by choosing y for enabling and n for disabling
BASIC_EXAMPLE = y
IIO_EXAMPLE = n

IIO Example

This project is an IIOD demo for the MAX31855PMB1 evaluation board. The project launches the IIOD server on the board so that the user may connect to it via an IIO client application. Using IIO-Oscilloscope, the user can read temperature samples from the device.

If you are not familiar with ADI IIO Application, please take a look at: IIO No-OS

If you are not familiar with ADI IIO-Oscilloscope Client, please take a look at: IIO Oscilloscope

In order to build the IIO project make sure you have the following configuration in the Makefile:

# Select the example you want to enable by choosing y for enabling and n for disabling
BASIC_EXAMPLE = n
IIO_EXAMPLE = y

No-OS Supported Platforms

Maxim Platform

Used Hardware

  • MAX31855PMB1

  • MAX32655FTHR or MAX32650FTHR

  • FTHR-PMD-INTZ

  • MAX32625PICO (required for MAX32650FTHR debugging)

Connections

MAX32655FTHR

  1. Connect the MAX32655FTHR with the FTHR-PMD-INTZ. The Maxim feather board should have stacking headers where the interposer board will be connected.

  2. Connect the MAX31855PMB1 to the FTHR-PMD-INTZ SPI PMOD connector.

MAX31855PMB1

FTHR-PMD-INTZ SPI

Pin 1 (Chip Enable)

CS

Pin 2 (Not connected)

MOSI

Pin 3 (MISO)

MISO

Pin 4 (SCK)

SCK

Pin 5 (GND)

GND

Pin 6 (VCC)

VCC

  1. Power up the MAX32655FTHR by connecting it to the PC using a micro-USB cable.

MAX32650FTHR

  1. Using a 10-pin ribbon cable, connect the MAX32625PICO to the MAX32650FTHR.

  2. Connect the MAX32650FTHR to the FTHR-PMD-INTZ.

  3. Connect the MAX31855PMB1 to the FTHR-PMD-INTZ SPI PMOD connector using the same pinout table above.

  4. Power up the MAX32650FTHR by connecting it to the PC using micro-USB. Connect the MAX32625PICO to the PC as well.

Build Command

# remove sp characters from the build directory
make reset
# build the project
make PLATFORM=maxim TARGET=max32650
# flash the code
make run