JURA Protocol

C++ JURA protocol implementation for controlling a Jura coffee maker over a serial (UART) connection.

This work is based on the excellent work done by the people over at Protocol JURA. They were able to figure out the basic protocol used for communication with older JURA coffee makers.

Since newer models do not use this old V1-Protocol any more I started this project to understand the new one and create a reference implementation for it.

Table of Contents

0. Example
1. Protocol
2. JURA Commands
3. Requirements
4. Building

Example

The following example shows the interaction with a JURA coffee maker over XMPP. The complete implementation for this demo can be found here.

Protocol

General

There are several steps of obfuscation being done by the JURA coffee maker to prevent others from reading the bare protocol.

Connecting to an JURA coffee maker

To connect to an JURA coffee maker we are using a 5V UART signal with the following configuration:

• Baud Rate: 9600
• Data Bits: 8
• Parity: Disabled
• Stop Bits: 1
• Flow Control: Hardware flow control disabled
• RX Flow Control Threshold: 0

Deobfuscating

Once a connection has been established we can start sending and receiving data.
But all data send and received is obfuscated. The following description shows how to deobfuscate data received from the coffee maker.
To obfuscate data just follow the steps in reverse.

Step 0 The coffee maker always sends 4 "raw" byte per one byte of data with a break of 8ms in between each "raw" byte. This looks something like this:

01011011 <8ms break> 01011111 <8ms break> 01011111 <8ms break> 01011111 <8ms break>
01011111 <8ms break> 01111011 <8ms break> 01011111 <8ms break> 01011111 <8ms break>
01111011 <8ms break> 01111011 <8ms break> 01111111 <8ms break> 01011011 <8ms break>
01011111 <8ms break> 01111111 <8ms break> 01011011 <8ms break> 01011011 <8ms break>
01111011 <8ms break> 01111011 <8ms break> 01011011 <8ms break> 01011011 <8ms break>

Each line corresponds to one actual data byte.

Step 1
Each of our 4 "raw" bytes (each line) contains only 2 bits of our resulting data bit.
Bit 2 and 5.
All other bits (except 0) are set to 1.

0b01011011
    ^  ^
  DB1  DB2

DB1 and DB2 are our actual data bits here. We have to combine alle 8 (of our 4 "raw" bytes) into a single data byte.

Examples:

const std::array<uint8_t, 4> encData{0b01011011, 0b01011111, 0b01011111, 0b01011111};

// Bit mask for the 2. bit from the left:
constexpr uint8_t B2_MASK = (0b10000000 >> 2);

// Bit mask for the 5. bit from the left:
constexpr uint8_t B5_MASK = (0b10000000 >> 5);

uint8_t decData = 0;
decData |= (encData[0] & B2_MASK) << 2;
decData |= (encData[0] & B5_MASK) << 4;
decData |= (encData[1] & B2_MASK);
decData |= (encData[1] & B5_MASK) << 2;
decData |= (encData[2] & B2_MASK) >> 2;
decData |= (encData[2] & B5_MASK);
decData |= (encData[3] & B2_MASK) >> 4;
decData |= (encData[3] & B5_MASK) >> 2; // 0b00010101

Input            -> Output
0 0 0 1  0 1 0 1 -> 0 1 0 1  0 0 0 1
0 1 1 0  0 1 0 1 -> 0 1 0 1  0 1 1 0
1 0 1 0  1 1 0 0 -> 1 1 0 0  1 0 1 0
0 1 1 1  0 0 0 0 -> 0 0 0 0  0 1 1 1
1 0 1 0  0 0 0 0 -> 0 0 0 0  1 0 1 0

Step 2
In this step we switch both nibbles (4 bit) of each byte. Examples: 1100 1100 -> 0011 0011

uint8_t in = 0b00010101;
uint8_t out = ((in & 0xF0) >> 4) | ((in & 0x0F) << 4); // 0b01010001

Input                                                                               -> Output
01011011 <8ms break> 01011111 <8ms break> 01011111 <8ms break> 01011111 <8ms break> -> 0 1 0 1  0 0 0 1
01011111 <8ms break> 01111011 <8ms break> 01011111 <8ms break> 01011111 <8ms break> -> 0 1 0 1  0 1 1 0
01111011 <8ms break> 01111011 <8ms break> 01111111 <8ms break> 01011011 <8ms break> -> 1 1 0 0  1 0 1 0
01011111 <8ms break> 01111111 <8ms break> 01011011 <8ms break> 01011011 <8ms break> -> 0 0 0 0  0 1 1 1
01111011 <8ms break> 01111011 <8ms break> 01011011 <8ms break> 01011011 <8ms break> -> 0 0 0 0  1 0 1 0

Step 3
A last time we have to shift all bits in our byte around. Here we have to split up our byte into two nibbles (4 bit) and switch two bits each.
Examples: 1100 1100 -> 0011 0011

uint8_t in = 0b01010001;
uint8_t out = ((in & 0xC0) >> 2) | ((in & 0x30) << 2) | ((in & 0x0C) >> 2) | ((in & 0x03) << 2); // 0b01010100

Input            -> Output           -> Output_Hex Output_Dec Output_Char
0 1 0 1  0 0 0 1 -> 0 1 0 1  0 1 0 0 -> 54  84  T 
0 1 0 1  0 1 1 0 -> 0 1 0 1  1 0 0 1 -> 59  89  Y 
1 1 0 0  1 0 1 0 -> 0 0 1 1  1 0 1 0 -> 3A  58  :
0 0 0 0  0 1 1 1 -> 0 0 0 0  1 1 0 1 -> 0d  13  '\r'
0 0 0 0  1 0 1 0 -> 0 0 0 0  1 0 1 0 -> 0a  10  '\n'

Which results in the message TY:\r\n.

JURA Commands

Every message/command send from or to the coffee maker has to end with \r\n to be valid. For simplicity reasons we omit the \r\n from all of the following messages and examples.

Command Structure

In general for every valid command a response will be send from the coffee maker. The actual command is always uppercase (e.g. TY:) and the response send back is lowercase (ty:EF532M V02.03).

Available Commands

The following list of commands has been tested on an Jura E6 2019 platin (15326).

Coffee Brewing Sequence

• FN:07 # Grind on
• Sleep 3 seconds # Determines how strong the coffee will be
• FN:08 # Grind off
• FN:22 # Brew group to brewing position
• FN:0B # Coffee press on
• Sleep 0.5 seconds # Compress the coffee
• FN:0C # Coffee press off
• FN:03 # Turn on the coffee water heater
• FN:01 # Coffee water pump on
• Sleep 2 seconds # Initial amount of water
• FN:02 # Coffee water pump off
• FN:04 # Turn off the coffee water heater
• Sleep 2 seconds # Allow the water to run everywhere
• FN:03 # Turn on the coffee water heater
• FN:01 # Coffee water pump on
• Sleep 40 seconds # 40 seconds of water result in 200 ml of coffee
• FN:02 # Coffee water pump off
• FN:04 # Turn off the coffee water heater
• FN:0D # Reset the brew group and throw out the old coffee grain

Requirements

The following requirements are required to build this project.

• A C++20 compatible compiler like gcc or clang
• The build system is written using CMake
• For managing dependencies in CMake, we are using conan

Fedora

To install those dependencies on Fedora, run the following commands:

sudo dnf install -y gcc clang cmake python3 python3-pip
pip install --user conan==1.59.0 # conan 2.x.x is not supported right now

Raspberry Pi

To install those dependencies on a Raspberry Pi, running the Raspberry Pi OS, run the following commands:

sudo apt install -y cmake python3 python3-pip
pip3 install --user conan==1.59.0 # conan 2.x.x is not supported right now

For all the other requirements, head over here: https://github.com/Jutta-Proto/hardware-pi#raspberry-pi-os

Building

Run the following commands to build this project:

# Clone the repository:
git clone https://github.com/Jutta-Proto/protocol-cpp.git
# Switch into the newly cloned repository:
cd protocol-cpp
# Build the project:
mkdir build
cd build
cmake ..
cmake --build .

[1]: https://uk.jura.com/en/homeproducts/accessories/SmartConnect-Main-72167