Sensors And everything else that plugs into input ports on the EV3

• Types of Sensors
  • Analog Sensors
  • LEGO NXT Color Sensor
  • I2C Sensors
  • UART Sensors
• Using Sensors
  • Automatic Detection
  • General resources
  • I2C sensor resources (applies to both NXT/I2C and Other/I2C)
  • Sensor-specific resources
• Unsupported Sensors
• Supported Sensors

The EV3 has four input ports for connecting sensors and other devices (like sensor multiplexers or motor controllers). If you are trying to use something that plugs into one of those ports, you are in the right place.

Types of Sensors

When dealing with sensors in ev3dev, it is useful to know how it communicates with the EV3 brick. There are four basic kinds of communication that the input ports can use to get information from the sensor: analog, NXT Color Sensor, I2C and UART.

Analog Sensors

These are the simplest type of sensor. The measured value is converted to a voltage (0-5VDC) that is read by the EV3. There are actually two types of analog sensors. We call the first EV3/Analog. These are sensors that were designed specifically for the EV3 and will not work on the NXT because the pinout is different. They contain an ID resistor so that the EV3 can tell different types of sensors apart. The second type is NXT/Analog. These sensors are designed for the NXT, but also work on the EV3. The EV3 cannot differentiate between most of these sensors though, so you have to tell it which one your have or just use the generic driver.

WeDo sensors, referred to as WeDo/Analog, are also analog sensors. They are actually electrically similar to EV3/Analog sensors (require 5V power and have ID resistor). Currently, we only support WeDo sensors attached to a WeDo hub, but if someone would like to design a cable and modify the wedo-sensor and lego-ports drivers, we could easily make them work with the input ports on the EV3.

RCX sensors also fall into this category, but do not work with the EV3 - at least not with the converter cable described in the NXT Hardware Developers kit. This is due to a difference in the input port pins between the EV3 and the NXT. If someone wants design a new converter cable, we could make them work.

LEGO NXT Color Sensor

The LEGO NXT Color Sensor is in a class of its own. It uses a hybrid of analog and (non-standard) digital communications. The NXT Color Sensor is not usable at this point in time. We can detect it with the auto-detect, but we don’t have a driver for it yet.

I2C Sensors

I2C sensors are sensors that communicate with the intelligent brick via the I2C protocol. In the NXT documentation, they are referred to a “digital” sensors. These sensors can be sorted into two categories as well: those that were designed using LEGO’s guidelines and those that use an off the shelf I2C chip. ev3dev supports both kind of sensors, but only the first type is auto-detected. We will refer to the former as NXT/I2C and the latter as Other/I2C

UART Sensors

These is a new type of sensor that is designed specifically for the EV3 (they don’t work with the NXT). They use an UART to send data to the brick. These sensors are a bit “smarter” in that in addition to sending the data of what they measure, they also send information about their capabilities. This means that any new EV3/UART sensors should “just work” without us having to write new drivers. Since the ‘U’ in UART means universal, this also means that EV3/UART sensors can connect to any UART device, not just the input ports.

Using Sensors

Automatic Detection

The EV3 has “smart” sensor ports that can identify most sensors. Beware! Full automatic detection works on EV3 only. And even on EV3, some sensors cannot be automatically detected. See notes below in the table of supported sensors.

For sensors that cannot be automatically detected, you can manually control the input port mode. Read more about it on [the lego-port class page][lego-port-class].

On FatcatLab’s EVB, only EV3 sensors can be automatically detected. For all NXT sensors, you must manually set the mode. (I2C sensors currently do not work on the EVB platform).

On BrickPi, sensors cannot be automatically detected at all. You must manually configure the input ports for all sensors.

On PiStorms, detection of EV3/UART, EV3/Analog and NXT/I2C sensors is semi-automatic. If you put the input port into ev3-uart, ev3-analog, or i2c-thru mode, the specific type of sensor will be automatically detected (assuming it is a LEGO compatible sensor). So you don’t have to write to the set_mode attribute of the port for these sensors.

General resources

• The LEGO Sensor (lego-sensor) Class
• EV3 Input Port Driver

I2C sensor resources (applies to both NXT/I2C and Other/I2C)

• I2C Sensor Addressing
• Using I2C Sensors

Sensor-specific resources

• Follow the links in the Supported Sensors table below

Unsupported Sensors

One of the goals of ev3dev is to support as many sensors as possible. In fact, even if a manufacturer’s documentation says that a device does not work with the EV3, chances are it will work with ev3dev.

If you have a sensor that is not supported yet, let us know about it by opening an issue on GitHub. For many sensors adding a driver is trivial - even if you are not a “kernel hacker” or a “c programmer”. For the non-trivial sensors, see the contributing page for information on how to write a driver or how to donate hardware to someone who will.

Supported Sensors

This is a list of sensors that currently have drivers available in the ev3dev kernel.