Overview

This Raspberry Pi HAT （Raspberry Pi not included) makes it easy to interface your Raspberry Pi with an electric vehicle's charge port and lets you program your own AC or DC fast charging communication controller.

In detail it provides a generator for the Control Pilot (CP) signal according to SAE J1772 and IEC 61851 for AC charging.

For DC charging according to the Combined Charging System (CCS) it additionally contains a PLC Modem that is exposed to the Linux kernel as a virtual Ethernet interface.

NOTE: This is not a finished product for a charging station. It is intended to be used as a development and or experimentation platform for ISO 15118 and DIN SPEC 70121. It contains hardware interfaces and driver configuration for this purpose but it does not come with an application software for the charging protocol. However, there are open source projects that offer suitable software stacks：

• https://github.com/qca/open-plc-utils
• https://github.com/V2GClarity/RISE-V2G

For details see Application Note RiseV2G & open-plc-utils

Features

• IEC 61851 compatible Control Pilot (CP) generation via STM8 micro controller (1kHz, +/-12V)
• Qualcomm QCA 7000 HomePlug Greenphy PLC Modem (optional order code!)
• 3 LEDs to indicate CP status (A/B/C)
• Readout of positive and negative Control Pilot voltage via I2C
• 0% to 100% settable Control Pilot duty cycle via I2C
• Control Pilot generator circuit and PLC modem detachable via jumper (Sniffer Mode)
• Automatic driver configuration of Raspberry Pi via preconfigured I2C EEPROM (plug&play)
• SWD pins to reprogram STM8 micro controller for custom applications
• UART attachable to STM8 micro controller via jumper

Detailed Description

Schematic Overview

• An STM8 micro controller creates a PWM signal that then gets boosted from +3.3V to +/- 12V in order to create the CP signal that is compatible to IEC 61851 (see below).
• The Raspberry Pi communicates via I2C what PWM percentage the signal should have. In addition it can also read out the present voltage level on the CP signal via I2C interface.
• The PLC modem can be connected to the CP signal by jumper pins and the the Raspberry Pi exposes a virtual Ethernet interface over which the TCP/IP communication can be established with a compatible car.
• The drivers for the PLC modem are stored in an EEPROM and get loaded automatically by the Raspbian Linux Kernel upon bootup
• The 3 screw terminals expose GND, CP and PLC connections

Electrical characteristics:

Use Cases

Use Case: Charging Station

This simple example use case shows how to wire the the Raspberry Pi in combination with this HAT to create a simple charging station.

Here the Raspberry Pi could for example control when the car charges and how much power it consumes by controlling the CP signal or establishing a TCP connection if the car supports it.

The relays could also be controlled by the Raspberry Pi with a simple board like this: Amazon Link

Use Case Pen-Test

If you are a security researcher it can also help you to do penetration testing and security analysis for the digital charging communication protocol of electric vehicles.

Use Case Sniffer

In order to analyze CCS digital charging Communication between a car and a charging station, the CP generator circuit can also be decoupled and this the PLC modem can be used to listen to the charging communication.

For details on how to do this exactly you can check out this github repository.

EV charging background information

Electric vehicles can be charged in two different ways:

1. AC charging. Called this way since the energy coming into the car is in the form of Alternating Current. But since a battery can only be charged by DC or Direct Current the car must contain a converter circuit. This only requires a relatively simple PWM circuit (also called Control Pilot or CP) that signals the car how fast it can draw the energy from the grid in order to not overload it.

2. DC (fast) charging. Called this way because, the energy coming into the car is in the form of Direct Current, which can be used by the car’s battery without conversion. But because the power grid transports its energy in AC, the charging station must provide a conversion to matches the car’s DC battery. Now that this conversion is taken care of outside the car, these conversion circuits can be much bigger and more powerful, therefore providing fast charging capability.

Charging Standards:

1. AC charging standards: The most widespread standard is the IEC 61851 which most importantly describes a simple PWM method to signal the car how fast it can draw energy (see circuit diagram below). This is there to prevent the car from overloading household electric circuits and prevent fires. In addition, it also signals the charging station when a car is actually connected and wants to be charged. This helps prevent electric shock.

   • Although the communication principles is the same, countries adopted different plug types:

   

   • Basic Circuit Wikipedia:

   

2. DC Charging standards: Unfortunately for DC charging there exist 3 major standards that are widely incompatible in regards to charging communication and plug types.

   • CHAdeMO: This is a standard developed mainly by Japan and thus often found on Japanese cars. It uses CAN communication and other signal lines between car and charging station for signaling.
   • GB/T: This abbreviation is often used to describe the Chinese DC charging standard. It also uses CAN like the Japanese Chademo standard but uses different messages and a different plug.
   • CCS: This stands for Combined Charging Systems. Called this way because it uses an extension of the AC plug with additional lines for DC power and communicates over the same signal lines as AC charging but overlays a digital PLC (Power Line Communication) signal over the PWM, which exchanges information using TCP/IP and a binary XML based messaging (EXI) between car and charging station.
   • Plugs:

   

3. Tesla: This is a bit of a special case. Since Tesla has offered electric cars before most of the standards were officially implemented Tesla had to develop their own charging methods and plugs.

   In the United States Tesla is still using their own plug and communicates via a proprietary CAN interface with their charging stations.

   In Europe, Tesla also started out with their own proprietary charging interface but by now adopted to be CCS compatible. This means that Tesla can charge AC and DC at non Tesla public charging infrastructure as well as their own. Unfortunately, even though the plug is identical on Tesla and CCS fast charging stations, the communication protocol is still proprietary. It appears to be largely based on the CCS standards and therefore TCP/IP as screw-ups on Tesla's charge network have shown when it was temporarily possible to charge other cars at Tesla stations for free.