---
name: "max31855"
section: "9"
platform: "linux"
package: "linuxcnc-uspace"
version: "1:2.9.4-2+deb13u1"
release: "Debian 13 (Trixie)"
platforms: ["linux"]
url: "https://new.carta.tech/max31855"
---

# max31855(9)

Support for the MAX31855 Thermocouple-to-Digital converter using bitbanged spi

## NAME

max31855 - Support for the MAX31855 Thermocouple-to-Digital converter using bitbanged spi

## SYNOPSIS

**loadrt max31855 \[count=*N*\|names=*name1*\[,*name2...*\]\] \[personality=*P1,P2,...*\]**

## DESCRIPTION

The component requires at least 3 pins to bitbang spi protocol, for example:

 **loadrt max31855 personality=1**

 **setp hm2\_6i25.0.gpio.023.is\_output true**  **setp hm2\_6i25.0.gpio.024.is\_output true**

 **net spi.clk.in    hm2\_6i25.0.gpio.023.out     max31855.0.clk.out**  **net spi.cs.in     hm2\_6i25.0.gpio.024.out     max31855.0.cs.out**  **net spi.data0.in  hm2\_6i25.0.gpio.033.in\_not  max31855.0.data.0.in**

 **addf max31855.0.bitbang-spi servo-thread**

The MAX31855 supports a range of -270C to 1800C, however linearization data  is only available for the -200C to 1350C range, beyond which raw temperature is returned.

Temperature pins are provided for readings in Celsius, Fahrenheit and Kelvin, temperature values are not updated while a fault condition is present.

The personality parameter is used to indicate the number of sensors. Multiple sensors share the clk and cs pins, but connect to discrete data input pins. A maximum of 15 sensors are supported.

## FUNCTIONS

- **max31855.***N***.bitbang-spi** (requires a floating-point thread)

  ## PINS

- **max31855.*N*.data.*M*.in bit in (M=0..( personality & 0xf ))**

  Pin(s) connected to data out.

- **max31855.*N*.cs.out bit out**

  Pin connected to cs, pulled low to shift data, pulled high for data refresh.

- **max31855.*N*.clk.out bit out**

  Pin connected to clk.

- **max31855.*N*.temp-celsius.*M* float out (M=0..( personality & 0xf ))**

  Temperature output values in Celsius.

- **max31855.*N*.temp-fahrenheit.*M* float out (M=0..( personality & 0xf ))**

  Temperature in Fahrenheit.

- **max31855.*N*.temp-kelvin.*M* float out (M=0..( personality & 0xf ))**

  Temperature in Kelvin.

- **max31855.*N*.fault.*M* bit out (M=0..( personality & 0xf ))**

  Fault condition detected.

- **max31855.*N*.fault-flags.*M* u32 out (M=0..( personality & 0xf ))**

  Fault flags: 0x1  = open sensor, 0x2 short to gnd, 0x3 short to vcc.

## AUTHOR

Joseph Calderon

## LICENSE

GPL