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!
Table of Contents
2. Electronic circuit
2.1 Driving voltage 0-5V from the computer
2.2 Controlling with a Relay
2.3 Controlling with TRIAC #1
2.4 Controlling with TRIAC #2
3.2 Device driver
3.3 Connecting with the Internet
4. Overdose symptoms
7.2 Authorship and maintenance
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
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
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.
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...
A popular variation of the above mentioned coffee. Actually, it
doesn't need a coffee-machine, rather a refrigerator for cold water
This is a difficult one, read coffee-faq (see references)
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.
(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. That´s 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
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 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
4.7K B |/ C
parallel port >-\/\/\/\/---| NPN Transistor: BC547A or 2N2222A
data pi |\ E
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
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, 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
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
You should change resistors accordingly for 220V.
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.,
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.
You will have to build an executable that will work like this:
· Get permission to use I/O address space, by calling kernel, with
the command ioperm: eg ioperm( BASE, range ,1);
· Perform an out request instruction, to set the 0-5V voltage to the
parallel port, eg outb( 1, BASE );
· Wait enough time so the coffee is made. It would be nice if that
time is read by looking at the command line.
· Then it will turn off the coffee-machine: outb( 0 , BASE );
· Before ending it should give back the parallel port with a ioperm(
BASE, range, 0);
Change BASE = 0x3bc for /dev/lp0, 0x378 for /dev/lp1, and 0x278 for
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
· tachycardia or cardiac arhythmia
· Hypersensibility to light
· Annoyance in respect with various audio stimuli
· gastrointestinal disturbance
These are our ideas:
· All hardware and software described here, can be expanded so that
it will support toast, beaf, applepies, etc.
· Cluster with 8 coffee-machines. This will let you have coffee even
when the first one gets off. Of course there will be a perfomance
· Parallel vector coffee-machine will be a future release.
· If you want the maximum automation you'll need more circuits and
sensors, so that you can control water flow, temperature, coffee
· In the near future we will implement SNMP features.
· Serial coffee-machine at 115Kbps.
· http://daisy.uwaterloo.ca/~alopez-o/caffaq.html This is most known
· http://faculty.washington.edu/chudler/caff.html Caffeine and
effects of on the Nervous System
· http://www.gardfoods.com/coffee/coffee.coffee.htm A pretty
comprehensive, if informal, history of humans' interaction with the
coffee plant. People have been chewing coffee berries in Africa
for 100,000 years or so. Coffee was definitely growing in Yemen,
where it is not native (so must have been planted), in 525 AD.
· http://www.faqs.org/rfcs/rfc2324.html RFC2324: Hyper Text Coffee
Pot Control Protocol (HTCPCP/1.0)
· http://www.faqs.org/rfcs/rfc2325.html RFC2325: Definitions of
Managed Objects for Drip-Type Heated Beverage Hardware Devices
Programming of I/O ports under popular operating system Linux.
· http://lonestar.texas.net/~andrew/f_pc_.htm A lot of circuits in
ASCII. Some of them are for parallel port.
· http://shell.rmi.net/~hisys/parport.html Whatever you wanted to
learn about a parallel port and didn't dare to ask.
· http://www.redhat.com:8080/HyperNews/get/khg.html How to write your
own device drivers. Come on, go ahead!
Tomi Engdahl's web page is a *must see* for everyone who enjoys
on-line. Unfortunatelly, there are no tests.
· http://www.cs.su.oz.au/~bob/coffee.html This coffee-machine offers
only cappuccino. It has to be upgraded.
· http://einstein.et.tudelft.nl/~janssen/ Hot coffee from
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
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.
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.
· Ethiopia: Identified as the originating country of coffee. As many
people corrected, coffee did not originally come from America nor
was brought by Christofer Colombus. It was popular in the Middle
East long before America was discovered. Still, we can remember
Cristobal Colon, as the person who brought tobacco and chocolate in
· Kostas Lialiambis is the one who dared saying that he can't make
coffee with his Linux box.
· Panagiotis Vrionis, Yannakopoulos Haralambos, for giving me
interesting and humorous notes.
· NUMEROUS people on the internet with additions and remarks.