Fotis Georgatos, <>
Annie Pinder, <>

v0.8, 30 November 2000

One of the most memorable comments about software I have ever heard, is whether this or that can make coffee. Coffee is a world commodity that is second only to oil. Linux DOES make coffee. And it tastes good, as well!

For a long time, humanity was wondering how could a computer make coffee... People need coffee wake up and stay awake in front of the computer for a long time. Everyone knows that coding is better at night...

The main problem is how to manage the coffee machine with the computer, so that it will be controlled by software. This generally means an ON/OFF switch implemented as a circuit which controls the coffee-machine's power supply.

This HOWTO has turned out in a public project, look at,

1. Menu

2. Electronic circuit

3. Software

4. Overdose symptoms

5. Expansions

6. References

7. etc

1. Menu

1.1 French

Popular coffee among programmers because doesn't need a lot of care; like commercial software. Its exciting taste has inspired thousands of programmers in writing incredible software, written in the very first ours of a day. Windows for example was written at 5:00 o'clock in the morning, Due to coffee! A result is guaranteed.

1.2 Nescafe

Nescafe is a rather strong coffee, made by pouring hot water in a mixture of coffee, sugar and some water. You usually take 1 spoon of coffee and 1 spoon of sugar with just a bit of water, to mix it. In the meantime you should have the water boiling. As soon as the water is hot enough, you mix them all together and preferably add milk. Although you can use something simpler than a coffee-machine to boil the water, I have seen this done many times...

1.3 Frappe

A popular variation of the above mentioned coffee. Actually, it doesn't need a coffee-machine, rather a refrigerator for cold water and ice-cubes.

1.4 Freddo

This is a difficult one, read coffee-faq (see references)

1.5 Espresso

Espresso is a very strong, italian sort of coffee. You serve it in small cups (You ask why? See chapter: Overdose Symptomes) with on or to pieces of lump sugar. To produce a good espresso you need fresh grinded coffee beans, water, lump sugar and a special machine. These machines boil the water and press the very hot steam through the grinded coffee beans. You can buy a super-duper-automatic machine for a lot of money. But a low cost machine is useable, too.

OK., lets start. Fill water in your machine. Let it become hot. In the meantime fill about 1 teespoon of coffeepowder in the filterhandle of your machine. Press the coffeepowder down. Not too much. Now the water is at the right temperature. Attach the filterhandle to the machine and let the machine work. After about 30 seconds you can serve a delicate, hot espresso. It is fine after a good meal. You feel good and can code for a few more hours.

1.6 Cappuccino

(See also chapter: Espresso) If you have a more profi-like machine, you can use it, to froth milk with it. You need this feature to make a creamy sort of coffee. It is easy to prepare. Put some frothed milk in a coffee pot and fill it up with espresso. Then decorade with some chokolade flakes. Thatīs it.

2. Electronic circuit

A general diagram is like this:

--------- 0-5V  --------- ~220V  ----------------
|  PC   |===>===|Circuit|========|Coffee-Machine|
---------       ---------        ----------------

The concept is that we take a controling voltage from the computer, which drives an electrically isolated circuit with a Relay or Triac.

You must choose a Relay circuit, if you have a coffee-machine greater than 200W. You can use a triac-based one if your coffee machine isn't high power.

All circuits presented are tested, but the results are YOUR RESPONSIBILITY. If you have no experience with electronics you should NOT try these, otherwise you may get a bad one...

You should be very careful while experimenting with 220V, and using an appropriate fuse is advisable.

2.1 Driving voltage 0-5V from the computer

Here is a simple example to get a voltage 0-5V from the parallel port of the computer.

      Back View          -----    Pin 10 - ACK
      Male DB-25         |   |    Pin  9 - D7
      Connector          |   |                           Pin 2 - D0
                         v   v                           v   Pin 1 -
      /                                                            \
      \     13  12  11  10   9   8   7   6   5   4   3   2   1     /
       \                                                          /
        \     25  24  23  22  21  20  19  18  17  16  15  14     /

Pin 1 is Strobe (inverse logic)

Pins 2-9 is DATA BUS's signals, exactly what was written to the parallel port's latches with an OUTB command.

Pin 10 is the acknowledge signal (ACK), controlled by you, so that you can produce an interrupt to the CPU.

Pins 18-25 are short-circuited and this is the ground (GND).

In detail:

<= in   DB25    Cent    Name of         Reg
=> out  pin     pin     Signal          Bit     Function Notes
------  ----    ----    --------        ---     -----------------------------
=>       1       1      -Strobe         C0-     Set Low pulse >0.5 us to send
=>       2       2      Data 0          D0      Set to least significant data
=>       3       3      Data 1          D1      ...
=>       4       4      Data 2          D2      ...
=>       5       5      Data 3          D3      ...
=>       6       6      Data 4          D4      ...
=>       7       7      Data 5          D5      ...
=>       8       8      Data 6          D6      ...
=>       9       9      Data 7          D7      Set to most significant data
<=      10      10      -Ack            S6+ IRQ Low Pulse ~ 5 uS, after accept
<=      11      11      +Busy           S7-     High for Busy/Offline/Error
<=      12      12      +PaperEnd       S5+     High for out of paper
<=      13      13      +SelectIn       S4+     High for printer selected
=>      14      14      -AutoFd         C1-     Set Low to autofeed one line
<=      15      32      -Error          S3+     Low for Error/Offline/PaperEnd
=>      16      31      -Init           C2+     Set Low pulse > 50uS to init
=>      17      36      -Select         C3-     Set Low to select printer
==      18-25   19-30,  Ground

2.2 Controlling with a Relay

The simplest circuit that one can build is:

                              |    __|__
                            Relay   /^\  Diode 1N4002
                             Coil  /---\
                              |      |
                           | / 
                 4.7K    B |/  C
parallel port >-\/\/\/\/---|        NPN Transistor: BC547A or 2N2222A
data pi                    |\  E
                           | V
parallel port >--------------+
ground pin                   |
Connect Vcc with the same voltage as the relay type (usually 5 or 12V). Obviously, the relay's specifications should be scaled for your coffee-machine.

Barmen, tend to put the relay AFTER the transistor, at the emitter (E) pin instead of the collector (C) pin. This is bad practice because it biases the transistor badly, and may result in bad coffee :-). Diode 1N4002 is useful to protect the transistor from the relay's currents. If you don't use it the transistor will become dark and smelly...

2.3 Controlling with TRIAC #1

If you only want a simple circuit, you can use Motorola's triac driver MOC301[012], together with a general purpose TRIAC like SC141D. This method has the advantage that you don't need an extra power supply.

For non-inductive loads, this is the circuitry:

        270     1 +-------+ 6    180
  +5v -VAVAVA-----+       +----VAVAVA-----+-------------- Line Hot
                2 |  MOC  |               |
  TTL in ---------+ 3012  +nc            VA  SC141D
                  |       | 4           / |
                nc+       +------------/  |
                  +-------+               +----\/\/\/---- Line Neutral

If you are going to work with 220V, try to obtain a 3021. Inductive loads should be used in conjuction with bypass capacitors, see Motorola Application Note AN-780. Coffee-machines are mainly resistive loads and not inductive (like a motor), but who knows what yours is!

2.4 Controlling with TRIAC #2

|    180                      180            2.2k
+---/\/\/\----+-----+   +----/\/\/-+--/\/\/\---+-------> 120V
              |    1|   |6         |           |         Hot
              |    +=====+         |           | MT1
              |    | MC  | TRIAC   |          +-+
              |    | 3032| Driver  |        G | | TRIAC
              |    +=====+         |         /| |
              \    2|   |4         |        / +-+
       2N3904  |----+   |          |        |  | MT2
              /     |   +--------- | -------+  |
             V      \              |        |  |
             |      /              |        \  |
             |      \ 43    .01u  ---   10k /  |
             |      /       500V  ---       \  |
             |      |              |        /  |
             +------+              |        |  |            Neutral
             |                     +--------+--+---o    o--> 120V
             /                                      load
 >-/\/\--|  2N3904
You should change resistors accordingly for 220V.

Circuit description:

The MC3032 is an optoisolator TRIAC driver. The 180-ohm resistor sets the current for the LED emitter in the optoisolator. Change the value of this resistor - if necessary - to get a reasonable current (e.g., 15 mA).

Note that you cannot test this circuit without a load. The TRIAC will not switch unless connected to an AC voltage source, so you can't test it for simple switching without applying AC and a load. Note the 500V rating on the .01 cap.

3. Software

3.1 Software

You will have to build an executable that will work like this:

Change BASE = 0x3bc for /dev/lp0, 0x378 for /dev/lp1, and 0x278 for /dev/lp2, range=8.

It would be useful if you had that program setuid, so that everybody can drink coffee!

3.2 Device driver

Just read kernel hacker's guide, implement a device driver (it could even be user space I think). Please compile it as a module, so that we won't need a kernel compile in every update. Then write:

echo cappuccino >/dev/coffee

And you will have a hot cup of coffee in minutes! Remember to give the right permission to /dev/coffee, depending on whether you want only root making coffee or not.

The advantage of this method is that it supports feedback from the coffee-machine by using the ACK of parallel port, so that smart coffee-machines could produce an interrupt.

Do it as homework.

3.3 Connecting with the Internet

If you have implemented the C program (see above), you just have to write a simple CGI script to turn ON and OFF the coffee-machine. You should write some nice webpages, explaining how to make coffee, and put them on an apache web server...

4. Overdose symptoms

5. Expansions

These are our ideas:

6. References

7. etc

7.1 preface

This document was initially written as part of a small debate in the linux-greek-users list , whether linux can make coffee or not. It has been an article in our beautiful online magazine about Linux called magaz. Remember, that magaz is greek it will look like that to you.

7.2 Authorship and maintenance

My name is Fotis Georgatos and I have also been in the past busy with the greek documentation and wwwpages maintainance. I welcome submissions to this HOWTO, as long as you're not anxious about the changes.

I'm Annie Pinder and a coffee fan. I live in England. I made the language changes on this document. I'm currently in the English equivalent of High School, in my final compulsory year.

7.3 Copyrights

The casual copyright with everything you get with linux... To find it, you'll have to read all of HOWTOs and average out the most common. Otherwise, no, you cannot copy it.

7.4 Credits