Controlling Model Railway with FlashAir GPIO

Contributor: ayase hiro

Latest update: March 2016

Overview

Details

FlashAir CONFIG setting

To enable the GPIO of FlashAir, add 「IFMODE=1」 to the CONFIG file of SD_WLAN in a folder in the FlashAir.

ref. IFMODEof command.cgi

Connect FlashAir and Arduino

The GPIO terminal of the FlashAir is connected to the digital I/O pins of the Arduino.

Bit Assignment	FlashAir	Arduino
0x01	CMD	digital I/O pin No.2(D2)
0x02	D0	digital I/O pin No.3(D3)
0x04	D1	digital I/O pin No.4(D4)
0x08	D2	digital I/O pin No.5(D5)
0x10	D3	digital I/O pin No.6(D6)

In order to use an SD Card with Arudino, we used a SDcard DIP module from Akizuki .

ref. Akizuki SDcard DIP module

GPIO output of FlashAir

From a browser that can connect to the to FlashAir you can pass GPIO commands by accessing the appropriate URL such as http://flashair/command.cgi?op=190&CTRL=0x1f&DATA=0xXX, which set H/L output of GPIO pins. To make this less combersome, I made a JavaScript HTML file List.htm and put it on the FlashAir which has buttons a user can press to set the GPIO register and thus train operations accordingly.

JavaScript for Train Operation Webpage

<script language="javascript" type="text/javascript"> <!—
//Function:HTTP communication to FlashAir
function flashair_get( param ){
  var request = new XMLHttpRequest();
  request.open("GET", param, false);
  request.send(null);
} 

//Global variable definition
var send_mess = "http://flashair/command.cgi?op=190&CTRL=0x1f&DATA=0x"; 
var p = 0x00;  

//Function:to any port in the H/L
function gpio_onoff(port){
  switch( port ){
    case 1:  //Emergency stop
             p |= 0x01;
             document.getElementById('RUN_STOP').style.backgroundColor = '#aa0000';
             url = send_mess + p.toString(16);
             flashair_get(url);
             break; 
    case 20: //point control High： opposite direction
            (approx.)
    case 21:  //point control Low： default direction
            (approx.)
    case 30:  //running direction　High： right
            (approx.)
    case 31:  //running direction　Low： left
            (approx.)
    case 4:  //running control　High： speed up
            (approx.)
    case 5:  //running control　High： slow down
            (approx.)
    case 6:  //running control　Low： coasting
            (approx.)
    } 
    document.getElementById('RESULT').value = p.toString(16);
}
//-->
</script>

Definition of GPIO input status and behavior

In this case, five operations shown in the following table has been achieved so as to correspond to each GPIO. The operation when each GPIO has become HIGH defined as shown in the table below.In the case all of the GPIO is LOW, it has to maintain the current status( speed and direction ).

Bit Assignment	FlashAir	HIGH/LOW	Behavior
0x01	CMD	HIGH	Running stop of the model railway vehicle
0x02	D0	HIGH	To switch the direction of the point to the left.
		LOW	To switch the direction of the point to the right.
0x04	D1	HIGH	To the running direction of the railway model vehicle to the left.
		LOW	To the running direction of the railway model vehicle to the right.
0x08	D2	HIGH	Increase the running speed of the railway model vehicle.(speed up)
0x10	D3	HIGH	Reducing the running speed of the model railroad vehicle.(slow down)

Check GPIO input status on the Arduino

In Arduino, always check the GPIO input status of FlashAir in a loop function. Check the status of No.2~6 pins of H/L of digital I/O, so that you designated operation is performed.

const int sdcard_gpio_pin[5] = { 2, 3, 4, 5, 6 };
const int sdcard_gpio_pin_num = 5;
void loop() {  
  for(int idx=0; idx < sdcard_gpio_pin_num; idx++)
  {
    if(digitalRead(sdcard_gpio_pin[idx]) == HIGH){
      if(idx == 0){
        funcspeed_stop();
        status_stop = 1;
      }
      else if(idx == 1){
        pointswitch(1); 
      }
      else if(idx == 2){
        if(status_LR != 1){
          status_LR = 1;
        }
      }
      else if(idx == 3){
        funcspeed(0); //slow down
      }
      else if(idx == 4){
        funcspeed(1); //speed up
      }
    }
    else{
      if(idx == 0){
        status_stop = 0;
      }
      else if(idx == 1){
        pointswitch(0);
      }
      else if(idx == 2){
        if(status_LR != 0){
          status_LR = 0;
        }
      }
    }
  }
}

Let's Get Moving

The output of the full-bridge driver for the PWM output that is connected to the railway input and the output of the full-bridge driver for point conversion to connected to that point. We are using a Kato Precision Railroad Models (KATO) set but you can connect other sets in the same way, such as Tommy Tech (TOMIX).

In the photo, a personal computer is connected for debugging with the serial monitor, it is not needed for the operation of the model railway. In addition, the iPad connected to the FlashAir displaying the operation web page described above.

Operating the model train with a FlashAir can be seen in this video:

Conclusion

In this case you can operate the model railway as driving the motor by the PWM output of the Arduino. For example, it would also be possible to operate a model car with a FlashAir.