A Cloud Hardware-Software Innovation Project for a Solar Powers Distributor

The project began with the clear goal of developing a reliable electric vehicle charging station (EVSE) for private use. It has to be compatible with the SAE J1772 standard and capable of reporting energy consumption to the cloud. The device also needed to offer local control through BLE when cloud connectivity was unavailable.

Power and Communication Board Development

We started by designing the two main components of the system: the Power Board and the Communication Board.

The Power Board, based on an STM32 microcontroller, was responsible for managing the relays that control charging and for measuring the energy consumed during the charging process. 

The board needed to accurately handle three-phase current measurement, which involved developing complex algorithms. The task required fine-tuning to make sure the board could accurately capture and report energy data while maintaining safety standards, especially during periods of high current load.

The ESP32-based Communication Board was the bridge between the EVSE and the cloud. 

This board handled data transmission via Wi-Fi and Ethernet, allowing users to monitor and control the EVSE remotely through the cloud. The board was also tasked with sending regular status updates and energy consumption data to the cloud using the MQTT protocol.

Initially, synchronizing the communication between the Power Board and the Communication Board proved challenging. The boards communicated using a UART interface, but timing led to synchronization issues, which disrupted data transmission. After identifying the problem, we adjusted the communication protocol and added error-checking mechanisms.

Cloud Integration and BLE Support

Once the basic functionality of the Power and Communication Boards was established, we moved on to connecting the device to the AWS IoT cloud. This involved setting up secure MQTT communication so the EVSE could send data like energy usage, device status, and charging information to the cloud in real time.

Using MQTT, the EVSE sent regular updates to the cloud every 60 seconds. These updates included data on current consumption, the total energy used during the charging session, and the device’s operating temperature. Users could access this data via a web dashboard or a mobile app, which allowed full remote control and monitoring of the charging station.

One problem we encountered was making sure the device could communicate with the cloud reliably, especially in areas with weak Wi-Fi. The device needed both Wi-Fi and Ethernet as backup options. During testing, switching between these connections caused delays and data loss. We fixed this by setting up the board to keep a stable connection no matter the method used, discreetly switching between Wi-Fi and Ethernet.

Besides cloud communication, we implemented Bluetooth Low Energy (BLE) support. This allowed users to control the charging station locally if the cloud connection was unavailable. BLE was important for initial configuration, where users could set up the network and access basic EVSE parameters directly from their mobile devices.

Initially, we encountered security issues with the BLE pairing process. The BLE system required pairing to establish a secure connection between the user’s device and the EVSE, but the initial pairing mechanism lacked sufficient security measures. The solution involved implementing a passkey system to enforce secure connections.

Web Interface

To make the setup simple, we added a basic web interface on the Communication Board. This interface lets users easily set up network settings like Wi-Fi credentials and check important EVSE status information. It also provided options for those needing more control to adjust the charging current and view diagnostic data.

NFC Support

The final key feature was adding NFC and RFID tag support. This allowed users to start or stop charging sessions by tapping an NFC tag. It was necessary for user authentication and added convenience for people who may not always have access to their phones or the cloud.

The integration of NFC tags had several issues that we needed to fix. At first, the NFC antenna wasn’t strong enough to reliably read some tags. To solve this, we improved the antenna design by following the PN7150 development kit guidelines, which boosted the signal and fixed the detection problem.

Safety and Compliance

We also faced challenges in making sure the EVSE met all safety and certification standards. We needed to pass tests like electrical safety, electromagnetic compatibility (EMC), and functional safety checks. These tests were required to confirm the product was safe and reliable for users. We also developed fault-detection systems to spot problems like ground faults or overheating. 

These safety features were tested thoroughly to meet the highest standards.