Input / Output Ports¶
This page is about the kind of ports that you plug sensors and motors into. Ports that have more than one connection type will have drivers that let you control the port itself. The input and output ports on the EV3 itself and some sensor multiplexers fall into this category (see list below). Simple multiplexers that only support one connection type will not have a separate driver for the port.
Input Port 5 on the BrickPi is physically wired to the I2C pins on the RaspberryPi. See BrickPi Input Port 5 for the details.
Port drivers use the lego-port-class to provide a common interface for interacting with individual ports. Follow the link for more information.
List of port drivers¶
This is a list of port drivers that are currently available in the ev3dev kernel.
| Name | Description | Connection Types | Module |
|---|---|---|---|
pistorms-out-port |
mindsensors.com PiStorms Output Port | tacho-motor | pistorms |
ms-nxtmmx-out-port |
mindsensors.com NXTMMX Output Port | tacho-motor | ms-nxtmmx |
brickpi-out-port |
Dexter Industries BrickPi Output Port | tacho-motor, dc-motor, led | brickpi |
brickpi-in-port |
Dexter Industries BrickPi Input Port | NXT/Analog, NXT/I2C, EV3/Analog, EV3/UART | brickpi |
legoev3-input-port |
EV3 Input Port | NXT/Analog, NXT/I2C, Other/I2C, EV3/Analog, EV3/UART, Other/UART | legoev3_ports |
legoev3-output-port |
EV3 Output Port | tacho-motor, dc-motor, led | legoev3_ports |
ht-nxt-smux-port |
HiTechnic NXT Sensor Multiplexer Input Port | NXT/I2C, NXT/Analog | ht-nxt-smux |
evb-output-port |
EV3 Output Port | tacho-motor, dc-motor, led | evb_ports |
brickpi3-in-port |
Dexter Industries BrickPi3 Input Port | NXT/Analog, NXT/I2C, EV3/Analog, EV3/UART | brickpi3 |
brickpi3-out-port |
Dexter Industries BrickPi3 Output Port | tacho-motor, dc-motor, led | brickpi3 |
evb-input-port |
EV3 Input Port | NXT/Analog, NXT/I2C, Other/I2C, EV3/Analog, EV3/UART, Other/UART | evb_ports |
ms-ev3-smux-port |
mindsensors.com EV3 Sensor Multiplexer Input Port | EV3/UART, EV3/Analog | ms-ev3-smux |
wedo-port |
LEGO WeDo Port | WeDo/Analog, dc-motor, led | wedo |
pistorms-in-port |
mindsensors.com PiStorms Input Port | NXT/Analog, NXT/Color, NXT/I2C, Other/I2C, EV3/Analog, EV3/UART | pistorms |
The lego-port Subsystem¶
The lego-port class provides an interface for working with input and
output ports that are compatible with LEGO MINDSTORMS RCX/NXT/EV3, LEGO
WeDo and LEGO Power Functions sensors and motors. Supported devices include
the LEGO MINDSTORMS EV3 Intelligent Brick, the LEGO WeDo USB hub and
various sensor multiplexers from 3rd party manufacturers.
Some types of ports may have multiple modes of operation. For example, the input ports on the EV3 brick can communicate with sensors using UART, I2C or analog validate signals - but not all at the same time. Therefore there are multiple modes available to connect to the different types of sensors.
In most cases, ports are able to automatically detect what type of sensor
or motor is connected. In some cases though, this must be manually specified
using the mode and set_device attributes. The mode attribute
affects how the port communicates with the connected device. For example the
input ports on the EV3 brick can communicate using UART, I2C or analog
but not all at the same time, so the mode must be set to the one that is
voltages, appropriate for the connected sensor. The set_device attribute
is used to specify the exact type of sensor that is connected. Note: the
mode must be correctly set before setting the sensor type.
Sysfs¶
Ports can be found at /sys/class/lego-port/port<N> where <N> is
incremented each time a new port is registered.
Note
The number <N> is not related to the actual port at all - use
the address attribute to find a specific port.
| Attribute | Access | Description |
|---|---|---|
address |
read-only | Returns the name of the port. See individual driver documentation for the name that will be returned. |
driver_name |
read-only | Returns the name of the driver that loaded this device. You can find the complete list of drivers in the list of port drivers. |
modes |
read-only | Returns a space separated list of the available modes of the port. |
mode |
read/write | Reading returns the currently selected mode. Writing sets the mode. Generally speaking when the mode changes any sensor or motor devices associated with the port will be removed new ones loaded, however this will depend on the individual driver implementing this class. |
set_device |
write-only | For modes that support it, writing the name of a driver will cause a
new device to be registered for that driver and attached to this port.
For example, since the exact type of an NXT/Analog sensor cannot be
automatically detected, you must use this attribute to load the
correct driver. For I2C sensors, you must write the I2C address in
addition to the driver name. Returns -EOPNOTSUPP if setting a
device is not supported for the current mode of the port. |
status |
read-only | In most cases, reading status will return the same value as mode.
In cases where there is an auto mode additional values may be
returned, such as no-device or error. See individual port
driver documentation for the full list of possible values. |
Events¶
In addition to the usual add and remove events, the kernel change
event is emitted when mode or status changes.