Lego Mindstorms#RCX

The RCX ( Robotic Command Explorer ) of the Lego Mindstorms product line has a Renesas-H8/300-Mikrocontroller than CPU. It is programmed by a program using an IR interface from the PC to the CPU of the RCX is downloaded. Several development environments allow the programming, either by graphically assembling components or finished in a variety of high-level languages ​​.

After the program has started, the robot built with an RCX can act completely autonomously and react to external and internal events, according to the programming instructions. Furthermore, two or more RCX communicate with each other through the IR interface, enabling competitions and cooperations. The RCX has three motor outputs and three sensor inputs. The power control of the motor outputs via pulse width modulation.

Programming languages

The software provided allows you to put together with a graphical user interface programs from building blocks. For more complex tasks of the RCX using different programming languages ​​can be programmed, such as NQC.

  • Developed by Lego ( with graphical interface ): RCX code
  • ROBOLAB ( based on LabVIEW )
  • From other suppliers ( text-based ): leJOS - Programming in Java
  • NQC ( Not Quite C [ dt " Not quite C" ] )
  • BricxCC ( Bricx Command Center ) - development environment that facilitates working with NQC
  • BrickOS (formerly LegOS ) - Programming in C and C
  • Interactive C - Provides additional functions such as text output
  • Robot C - Controls various systems (including RCX and NXT )
  • From other suppliers ( with graphical interface ): Kara - Programming by means of finite state machines

RCX sensor inputs

For many hobbyists who want to develop their own sensors, it is interesting, the output from the RCX sensor value (0 ... 1023 ) to interpret. This value is derived from the pressure at the sensor input voltage. This sensor is not 5 V, but falls when a sensor having a finite resistance is connected. The display of the RCX can be calculated as follows from the applied voltage U:

The voltage U in turn can be calculated at the sensors, for example, from the connected resistor R and the electric current I. The maximum electric current is 0.5 mA ( the sensor is an internal 10 k-ohm resistor upstream ).

The sensors can be in an active ( light sensor, rotary sensor) and a passive mode (switches, temperature sensor ) are operated. In the passive mode is measured as described above, only the voltage drop at the sensor inputs. In the active mode is for each MS 3 on the battery voltage to the sensor input in order to provide the sensor with power. For 0.1 ms is then switched to the passive mode, to detect the sensor value. During this time, the active sensor has its own power source ( capacitor ) must provide.

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