Q&A B58 Sim Terms of use

RealSimControl - I/O Extensions

Input Extension board

The most important component used in the RealSimControl system for input expansion is the CD74HC4067 multiplexer. The CD74HC4067 module (16-channel multiplexer) is widely available online as a cheap breakout board (less than $1 for a piece). Also, you can use the 8-channel 74HC4051 multiplexers if needed.

CD74HC4067 works as simple multiposition electronic "switch" when only one port of 16 is selected with 4 address lines (S0 ... S3) at any given time.

So, you can connect 16 toggle switches or momentary buttons to the multiplexer inputs, or use appropriate number of inputs for rotary switches and encoders. All multiplexers used for inputs are connected to 4 common address lines: S0,S1,S2,S3 (or pins #22,23,24,25).


Outputs Extension for 7-segment displays

To extend a number of 7-segment displays in RealSimControl, the same CD74HC4067 module is used, but used as reversed (output) multiplexer. You can also use several multiplexers for output, but most likely only one output expansion board will be sufficient for your entire system (16 displays).

The difference from the input multiplexer is the connection and direction of signals, in this case Z (SIG) is used as input, and all 16 channels are used as outputs:

  • S0,S1,S2,S3 inputs are connected to the same common 4 address bus lines
  • SIG ("Z") should be connected to the one "S" line on the master board
  • "EN" input is connected to the output pin assigned for this output multiplexer board.
  • C0..C15 outputs are used as input control signals for 7-segment indicators

The RealSimControl firmware program receives formatted data from the plugin that need to be changed for particular display. In the moment when needed channel is opened it sends data for output device connected to the selected channel.


Note: Any single extension board can be used either for inputs or outputs only! Don't try to connect switches to output multiplexer.



Other Output Extensions

  • 1. RealSimControl supports multiple serial outputs (up to 64x LEDs for one signal line), for this you need to use LED drivers or shift registers (see the details in the Wiring Guides).
  • 2. RealSimControl also supports "LED matrix output" (up to 64x LEDs for one output), for this you need to use the MAX7219 controller .
  • 3. To extend the number of PWM outputs in RealSimControl use one 24-channel PWM driver TLC5947 ).

Slave controller Boards

  • 1. For stepper motors control additional RealSimControl Stepper controller board is used. It is one Uno or Nano Arduino board with special RealSimControl stepper control firmware uploaded to it from the RealSimControl plugin menu.
  • 2. For servo control additional RealSimControl Servo controller board is used. It is one Uno or Nano Arduino board with special RealSimControl Servo control firmware uploaded to it from the RealSimControl plugin menu. Also you can use the WitMotion 16-32-channel Servo Controllers.
  • 3. Support for Button Matrix Extension board, the "RealSimControl Matrix" firmware is added and the "Matrix" board is included in the configurator.

NOTE: Though the main input/output connection options mostly stay intact, the configuration protocol and hardware connections can be changed, sometimes drastically.
Please don't rush to make some kind of complex PCBs, modules for yourself (and especially proposing them to the community).

Besides, the RealSimControl architecture is specially designed the way when anyone can simply buy ready-to-use, cheap modules and breakout boards listed on this website and in the "Components" page, connect them as described on our pages, that's all.


Option: 8-channel extension boards

You can also use the 8-channel 74HC4051 multiplexer when you don't need many switches (or 7-segment displays) in one particular place. There is no difference in code performance because the firmware function always counts it as 16-channel MUX.

1) For 8-bit INPUT multiplexer board you should not connect the "EN" input to the "GND". Instead you need to use the first 3 bus address lines for S0..S2 and connect the 4-th address line to the "EN" input of this multiplexer board.

2) For 8-bit OUTPUT multiplexer board the address line S3 is not used at all.


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