Epson printer at #bcne3

Centronics Handsake

It turns out there are a number of ways to communicate with printers and the Epson supports a number of these methods. I decided to go with the Centronics standard AKA Compatibility Mode since its about as basic as you can get. Heres a diagram from the excellent http://www.beyondlogic.org

Centronics Handshake Diagram from beyondlogic.org

Think of the handshake as; you wait for the printer to be free (busy low) enter the number you want to send (set the 8 bits of your byte on the data lines) then pull the send lever old cash register style  (strobe low wait stobe high). Its not a partuclay dificult concept but I found the diagram hard to understand becuase for some reason I thought it had to be more complicated than it actualy was.

Wiring Up

Nothing too complex here the table below show the Socket to Arduino linkup:

You only need to wire up one of the ground lines since they will all be connected to ground in the printer anyway (lazy method)

Programming

Its worth pointing out at this stage that you might want to make up some kind of parallel port debuger so you can get an idea of whats actualy happening at a low level and that your program is producing the expected output.

First lets setup the pins as in the table above we will also setup a serial connection so we can do debugging.

int strobe = 12;
int busy = 11;
int ack = 10;

void setup()   {
  pinMode(strobe, OUTPUT);
  //setup stobe high
  digitalWrite(strobe, HIGH);
  //setup handshake listeners
  pinMode(busy, INPUT);
  pinMode(ack, INPUT);
  for(int i=2;i<10;i++){
     pinMode(i, OUTPUT);
     //setup inital condition
     digitalWrite(i, LOW);
  }
  Serial.begin(115200);
  Serial.println("READY:");
}

To start with we can actual simplify the handsake further by ignoring the ACK since BUSY should always go low when we are OK to send more data. With this in mind we end up with 3 main steps:

1. Wait for not busy
2. Set Data
3. Strobe

For the wait not busy function i decided to go with a simple poll, every 100 iterations it prints a ‘.’ so we can see in the terminal if its got stuck.

void pollWait(int port){
  int i = 0;
  while(digitalRead(port) == 1){
    i++;
    if(i>100){
      i=0;
     Serial.print(".");
    }
  }
}

Strobe function is nice and simple. Suposidly you can have any value greater than 0.5 microseconds for the strobe and it will work. To keep it simple i just went with 1ms.

void doStrobe(){
    digitalWrite(strobe, LOW);
    delay(1);
    digitalWrite(strobe, HIGH);
}

Setting the datalines we use i+2 as the first bit is written to pin 2 etc.

void setLines(byte out){
  //loop over data lines
  for(int i=0;i<8;i++){
    //check and set
   if(bitRead(out, i) == 1){
     //write to pint we start at 2 so +2
     digitalWrite(i+2, HIGH);
   }else{
     //bit is 0 so set low
     digitalWrite(i+2, LOW);
   }

  }
}

Now we use all these functions to send a byte to the printer

void dataHandShake(byte a){
    pollWait(busy);
    setLines(a);
    doStrobe();
}

Finaly we can make a small program to print somthing. Its worth making sure things only happen once… you dont want your printer spewing paper while you try and turn it off!

Add the following global:

    boolean go = true;

Then quick and dirty hello world:

void loop()
{
 //so we dont end up with a constant stream
 if(go){
     dataHandShake('H');
     dataHandShake('e');
     dataHandShake('l');
     dataHandShake('l');
     dataHandShake('o');
     dataHandShake(' ');
     dataHandShake('W');
     dataHandShake('o');
     dataHandShake('r');
     dataHandShake('l');
     dataHandShake('d');
     //send Line feed so it prints the line
     dataHandShake(0x0A);
     go = false;
     Serial.println("DONE");
   }
}

We now end up with somthing that looks like this:

Hello World!

Thats all for now in a future post (hopefully!) I will be looking at more advanced printing.

The plugin reached its first milestone and has been released here; http://forum.team-mediaportal.com/plugins-47/flicked-flickr-plugin-mediaportal-53103/

Currently im awaiting the release of media portal 1.0.1 before moving on with development due to the plugin/skin revamp.

Soft subs

I watch a bit of anime now and again a needed to use softsubs however media portal dosent really support this out of box. Bit of searching I came across this thread even though its for an older version the solution still works.

DVB-T EPG

This really annoyed me because I was stuck for so long and the solution was so simple! I was getting absolutly no information in my program guide  everything appeared to be setup to get the guide from DVB-T, the answer was to simply disable any encypted channels in the channel list in the TV (wiki link).

Now as you may know laptops are usually what some people might call “a bit of a bastard” when it comes to installing anything other than windows. Now I haven’t seriously used a Linux distro in about 3 years so I decided to check out one that I had heard a lot about recently; Ubuntu as it turned out this was a bit of a mistake the inital startup gladly informed me it was having trouble reading my floppy drive before dying horribly, not surprising really considering I don’t have one. Googling around for a bit revealed this was a known issue with my laptop the other being having the parallel port enabled in BIOS broke the sound card (WTF) with a lot of people not making much progress I decided to turn back to a distro I was familiar with Gentoo.

Gentoo’s inital kernel fired up ok and then came the fun bit; the install. Now Gentoo basically likes to compile everything and give you a load of options about how you set your system up, this is great if you have an old system and you want to install the minimum of stuff so it runs as fast as possible. The downside is it takes forever. Its not for the weak of heart but by the end you feel like you have achieved something and quite possibly learned something too. The main install guide ends with getting your system configured to your preference and fully bootable what it doesn’t do is tell you how to setup X, I really like this because as window managers go i love the little known fluxbox. Fluxbox is quite simple, lightweight and looks good too, its a brilliant window manager I used extensively during my uni days for development. Luckily someone that uses it likes it as much as i do and created a helpful guide for Gentoo users. Flux is .

Now theres quite a difference between setting up for fun and actually using it full time. Yesterday my main PC died the culprit; broken memory, result? one scrambled windows PC. With the postman a few days away I’m back on the laptop so I decide my desktop needs prittying up a bit this is where i hit a problem:


fbsetbg -f mybackground.jpg

produced something along the lines of:


Esetroot: unable to load image file

Helpful it wasn’t I found out that another program called feh could also be used to a background trying to find out if it was a general problem setting background feh firmly pointed the finger at imlib2. Emerging this imlib2 didn’t have any effect until I realised why apparently you need to do this:


USE="jpeg gif" emerge imlib2 --newuse

Now for people that don’t know how emerge works what its basiclay saying is install imlib2 with support for jpeg and gif files, now why it doesn’t do this as a matter of course ill never know and generally such questions are best left unanswered when it comes to Linux as usually there long and boring. In the end things turned out fairly nice: