protocol.md

Communication protocol (EP2220)

The underlining protocol used by this coffee machine is quite simple. The mainboard does all the heavy lifting and the display unit is only responsible for I/O. Upon powering on, the Display unit issues a 'power on' command and then continues to poll the machine status from the mainboard using a request message. The mainboard replies to this request with a message containing all LED states. If the user presses a button this this information is passed along in a message to the mainboard. Once the user releases the button the display returns to sending status requests. If the machine is off/sleeping no messages are sent in either direction. The messages were obtained by listening to the bus.

Messages from the display to the mainboard

All messages have the following structure:

Start Message	Content	Checksum
D5 55	00 01 02 00 02 00 00 00	11 36

The first 2 Bytes are always D5 55. The length of the message is not encoded but it also never changes. The last 2 Bytes are some sort of checksum. The rule for determining this checksum is not known.

Power on message

There seem to be 3 messages responsible for powering on the machine.

D5 55 0A 01 02 00 02 00 00 00 0E 12

Makes the machine beep, but does not actually power on the machine.

D5 55 01 01 02 00 02 00 00 00 25 27

Beeps and powers on the machine, but without a cleaning cycle during startup.

D5 55 02 01 02 00 02 00 00 00 38 15

Beeps, powers on the machine and includes a cycle during startup.

The last 2 Messages are used within this project. The 3rd byte is likely responsible for turning the coffee machine on, since it's 00 in all other messages.

Power off message

D5 55 00 01 02 00 02 01 00 00 1D 3B

When sent, the mainboard proceeds to shut down the machine. The display unit goes to sleep after powering off.

Status request message

D5 55 00 01 02 00 02 00 00 00 11 36

Play/Pause button message

D5 55 00 01 02 00 02 00 00 01 19 32

Drink selection

Byte nr. 8 is used to transmit drink selections. The 4 least significant bits are used. The bit indices and the resulting checksums are listed below.

Button	Message
Espresso	D5 55 00 01 02 00 02 02 00 00 09 2D
Hot Water	D5 55 00 01 02 00 02 04 00 00 21 01
coffee	D5 55 00 01 02 00 02 08 00 00 39 1C
steam	D5 55 00 01 02 00 02 10 00 00 09 26

Settings buttons

The 9th byte is used to transmit the right hand side button group in a similar fashion.

Button	Message
Bean	D5 55 00 01 02 00 02 00 02 00 09 2F
Size	D5 55 00 01 02 00 02 00 04 00 20 05
Aqua clean	D5 55 00 01 02 00 02 00 10 00 0D 36
Calc clean	D5 55 00 01 02 00 02 00 20 00 28 37

Play/Pause button

D5 55 00 01 02 00 02 00 00 01 19 32

Encoding simultaneous button presses

This should be possible but determining the correct checksum is required.

Messages from the mainboard to the display

All messages have the following structure:

Start Message	Content	Checksum
D5 55	00 00 00 00 00 00 00 00 00 00 00 00 00 00 00	39 0D

The structure is similar to the previous messages but the content part is longer. The message above means all LEDs on the display are turned off. The following table show the purpose of each byte and their known states

EP2220

Byte	Purpose	Detail
0	START
1	START
2	INSTRUCTION
3	Espresso-LED	03/07 - half/full brightness ; 38 - 2x espresso
4	Hot Water-LED	03/07 - half/full brightness
5	Coffee-LED	03/07 - half/full brightness; 38 - 2x coffee
6	Steam-LED	03/07 - half/full brightness
7		unknown - probably unused
8	Bean-LED	00 - 1 LED; 38 - 2 LEDs; 3F - 3 LEDs
9	Bean-LED	07 - show led group; 38 - powder selected
10	Size-LED	00 - 1 LED; 38 - 2 LEDs; 3F - 3 LEDs; 07 - Top LED
11	Size/AquaClean-LED	07 - show led group; 38 - aqua-clean-orange
12	Calc/Clean	00 - both off; 38 - calc/clean-orange; other states unknown
13		unknown - probably unused
14	Empty Water-LED	38 - water empty
15	Waste&Warning-LED	07 - waste; 38 - warning sign
16	Play/Pause-LED	07 - on
17	checksum
18	checksum

Off LED states

D5 55 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 39 0D

Idle LED states

D5 55 00 07 07 07 07 00 00 00 00 00 00 00 00 00 00 07 2B

Other machines

The EP2235 uses the same protocol as the EP2220 except for a couple of small differences. The Steam option has been replaced with Cappuccino.

EP2235

Byte	Purpose	Detail
0	START
1	START
2	INSTRUCTION
3	Espresso-LED	03/07 - half/full brightness ; 38 - 2x espresso
4	Hot Water-LED	03/07 - half/full brightness
5	Coffee-LED	03/07 - half/full brightness; 38 - 2x coffee
6	Cappuccino-LED	03/07 - half/full brightness;
7		unknown - probably unused
8	Bean-LED	00 - 1 LED; 38 - 2 LEDs; 3F - 3 LEDs
9	Bean-LED	07 - show led group; 38 - powder selected
10	Size-LED	00 - 1 LED; 38 - 2 LEDs; 3F - 3 LEDs; 07 - Top LED
11	Size/AquaClean-LED	07 - show led group; 38 - aqua-clean-orange
12	Calc/Clean	00 - both off; 38 - calc/clean-orange; other states unknown
13		unknown - probably unused
14	Empty Water-LED	38 - water empty
15	Waste&Warning-LED	07 - waste; 38 - warning sign
16	Play/Pause-LED	07 - on
17	checksum
18	checksum

EP3243/EP3246

The 3200 series follows a similar protocol schema but uses a new set of messages. Note that the milk option is always available when size selection is also available.

Byte	Purpose	Detail
0	START
1	START
2	INSTRUCTION
3	Espresso-LED	03/07 - half/full brightness ; 38 - 2x espresso
4	Cappuccino-LED	03/07 - half/full brightness
5	Coffee-LED	03/07 - half/full brightness; 38 - 2x coffee
6	Latte/Americano-LED	03/07 (half/full) - latte selected; 38 - Americano selected
7	Hot Water/ 2x Americano	07 - 2x Americano; 38 - Hot Water selected
8	Bean-LED	00 - 1 LED; 38 - 2 LEDs; 3F - 3 LEDs
9	Bean-LED	07 - show led group; 38 - powder selected
10	Size-LED	00 - 1 LED; 38 - 2 LEDs; 3F - 3 LEDs; 07 - Top LED
11	Size-AquaClean-LED	07 - show led group (size and milk); 38 - aqua-clean-orange
12	Calc/Clean	00 - both off; 38 - calc/clean-orange; other states unknown
13	Milk-LED	00 - 1 LED; 38 - 2 LEDs; 3F - 3 LEDs
14	Empty Water-LED	38 - water empty
15	Waste&Warning-LED	07 - waste; 38 - warning sign
16	Play/Pause-LED	07 - on
17	checksum
18	checksum

Messages from the display to the mainboard can be found here.