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.
This is a list of sensors that currently have drivers available in the ev3dev kernel. The Part Number column links to the vendor website. The Name column links to the sensor's entry in Appendix A.
.. lego-sensor-list::
| [1] | Only touch sensors that shipped with the NXT 2.0 set can be automatically detected. Older touch sensors that shipped with the original NXT sets are missing an electrical connection (pin 2 is not internally connected to pin 3) and cannot be automatically detected. |
| [2] | The automatic detection algorithm detects this sensor
as an NXT/Analog type sensor but it cannot determine
the exact sensor type. The generic analog driver (nxt-analog) will be
loaded by default for this sensor. See the :ref:`lego-port-class` for
information on how to manually load the correct driver. |
| [3] | The automatic detection algorithm detects this sensor as an I2C sensor and the port is automatically put into I2C mode. However, the sensor does not follow the LEGO MINDSTORMS convention for I2C sensors, so the exact type of sensor cannot be determined. See :doc:`i2c` for information on how to manually load the correct driver. |
| [4] | The automatic detection algorithm detects this sensor as an I2C sensor and the port is automatically put into I2C mode. However, this sensor only partially follows the LEGO MINDSTORMS convention for I2C sensors, so the driver must be loaded manually. See the sensor's page for more information. |
| [5] | The Dexter Industries dFlex sensor cannot be automatically
detected (because pin 2 is not connected to pin 3). In order to use this
sensor, you must manually set the port to nxt-analog mode and then set
the driver to di-dflex. |
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.
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 :doc:`ports` page.
On FatcatLab's EVB, EV3/Analog and EV3/UART sensors can be automatically detected. For NXT/Analog sensors, you must manually set the mode. Most NXT/I2C sensors should be automatically detected.
On BrickPi, BrickPi+ and BrickPi3, 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 usually don't have to write to
the set_device attribute of the port for these sensors.
Most of the supported sensors are designed to work with LEGO MINDSTORMS. These
sensors use the LEGO sensor class. You can find these
in sysfs at /sys/class/lego-sensor/. The sensors have modes that select
what type of data is read from the sensor. Generally, you will select a mode
and then read the data value from the sensor. Follow the link above for more
details.
Many sensors that were not specifically designed for LEGO MINDSTORMS can be used
with ev3dev too. You can read more about the "Other" sensor types below. Also,
some MINDSTORMS compatible sensor may have advanced features that are not
accessible using the lego-sensor class.
When using sensors this way, often automatic detection will not work correctly,
therefore it is usually best to manually select the mode of input port (e.g.
other-i2c or other-uart).
For more information on using I2C sensors, check out :doc:`i2c`.
When dealing with sensors in ev3dev, it is useful to know how it communicates with the EV3 brick. There are three basic kinds of communication that the input ports can use to get information from the sensor, Analog Sensors, I2C Sensors and UART Sensors, plus one special type for LEGO NXT Color Sensors.
These are the simplest type of sensor. The measured value is converted to a voltage (0-5VDC) that is read by the EV3.
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 actual analog value is measured on pin6.
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.
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.
WeDo sensors 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.
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 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.
These are sensors designed using LEGO's guidelines for NXT digital sensors. NXT/I2C sensors can be automatically detected because they contain vendor and product IDs at specific I2C registers.
These can be any off-the-shelf I2C device or 3rd party sensors that are designed for LEGO MINDSTORMS, but do not follow the guidelines of NXT/I2C sensors.
The EV3 has a UART transceiver connected to each input port that can be used to communicate with many devices using this widely used standard.
These is a new type of sensor that is designed specifically for the EV3 (they don't work with the NXT). 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.
In addition to sensors designed to work with EV3, any UART device can be connected. But, be careful of voltage levels. The EV3 uses 3.3V I/O. It is safe to connect other devices that use 3.3V or 5V I/O. But, don't connect anything with higher voltage!
.. kernel-doc:: sensors/lego_sensor_class.c :doc: userspace
The sensor drivers are implemented in the following modules:
.. kernel-doc:: sensors/ev3_analog_sensor_core.c :doc: userspace
.. kernel-doc:: sensors/ev3_uart_sensor_ld.c :doc: userspace
.. kernel-doc:: sensors/ev3_uart_sensor_core.c :doc: userspace
.. kernel-doc:: sensors/nxt_analog_sensor_core.c :doc: userspace
.. kernel-doc:: sensors/nxt_i2c_sensor_core.c :doc: userspace