Configuration options

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If you already have a FastCLock EX‑FastClock has a number of couple of configuration options which allow you to connect your own clock to a EX‑CommandStation.

The various configuration options are outlined below

Connecting your own FastClock

Connecting via Serial

Connecting via Serial is the simplest option if available.

  • Run a dupont cable from the TX pin on the arduino to a RX pin on the EX-CommandStation. It is not usually necessary to run a cable from RX to the TX on the EX-CommandStation as the FastClock is not receiving data back.

  • Find the Serial defines in the config.h file (or copy config.example.h to config.h if you dont have one), locate the following lines:

    //#define SERIAL1_COMMANDS
    //#define SERIAL2_COMMANDS
    //#define SERIAL3_COMMANDS

    and uncomment the appropriate one for the serial port you are using.

  • Add the following code to your Setup() function:

while (!Serial) {
; // wait for serial port to connect. Needed for native USB port only
  • Include the following routine within your code:

    void SendTime(byte hour, byte mins, byte speed) {
      int itime = (hour * 60) + mins;
      char buffer[20];
      sprintf(buffer, "<JC %d %d>", itime, speed);
  • Each time the time changes call the SendTime routine as follows:

    SendTime(HH, MM, clockSpeed);

    where HH = the hour, MM = minutes and clockSpeed = the fast speed (e.g. at spped 4, 15 seconds represents a minute).

Connecting via I2C

Connecting via I2C involves a HAL driver file to the EX‑CommandStation as well as adding some code to the existing FastClock code. Follow the following steps:

  • In the EX‑CommandStation code copy the file myHal.cpp_example.txt to myHal.cpp.

  • Edit the file myHal.cpp and uncomment the following line near the beginning of the file

    //  #include "IO_EXFastClock.h"  // FastClock driver
  • Uncomment the following line near the end of the file

    //  EXFastClock::create(0x55);

    0x55 (decimal 85) is the default address but needs to match that in the FastClock code (see below).

  • Using Dupont connectors connect SDA/SCL/Gnd on the clock to SDA/SCL/Gnd on the EX‑CommandStation

  • Include the following code in your FastClock code:

    Near the top of the sketch:

    #include <Wire.h>

    Within your Setup():


    Add the following function within the sketch

    void TransmitTime() {
        // send the data over I2C
        // send the time as <mmmm> as two bytes followed by clockspeed
        int timetosend = (HH * 60) + MM;
        byte TimeArray[2];
        TimeArray[0] = (timetosend >> 8);
        TimeArray[1] = timetosend & 0xFF;
        Wire.write(TimeArray, 2);

    In the function above HH is the time as hours (24hr. clock) and MM is the minutes.

  • The CommandStation-EX will now poll the FastClock to request the time. The frequency at which it does so is influenced by the clock speed (i.e. on a slow clock speed it polls less often).

Next Steps

Now that you know how to connect your existing FastCLock, click the “next” button see how you use EX‑FastClock.