What is it

Embedded

Hardware

+

// __attribute__((OS_main)) tells the compiler that this function never
// returns and saves us precious space
__attribute__((OS_main)) int main(void) {

    hal_init(&comm_byte_received_callback);

    // This is the main handling loop
    // It handles all packets that can arrive in the Normal mode
    while (1) {
        if (comm_wait_for_packet(&p[current_packet]) == 0) {
            switch (p[current_packet].id) {
                case packet_GET_STATUS:
                    sendACK();
                    break;
                case packet_RFID_SEND:
                    // We will send data from this packet, and replace them
                    // in-place with what we receive
                    hal_spi_begin_transaction();
                    for (uint8_t i = 0; i < p[current_packet].length; i++) {
                        p[current_packet].data[i] =
                            hal_spi_transfer(p[current_packet].data[i]);
                    }
                    hal_spi_end_transaction();
                    // And suddenly, we are a response packet :)
                    p[current_packet].id = packet_RFID_SEND_COMPLETE;
                    transmit_and_flip();
                    break;
                case packet_RX_ERROR:
                    // Retransmit the last packet
                    comm_transmit_packet(&p[current_packet ^ 1]);
                    break;
                default:
                    // Unacceptable packet was received in this mode
                    p[current_packet].id = packet_INVALID_PACKET;
                    p[current_packet].length = 0;
                    transmit_and_flip();
                    break;

Software

But we already have this system

How does it work?

System architecture

Server

Controller

Reader

Reader

• Reads ID from an ISIC card
• Blinks and beeps :)
• Uses our custom interface or USB
• ARM Cortex M0 MCU
• Programmed in C (+ ChibiOS)

Controller ↔ Reader

• Our custom interface
• Simple to setup from available components
• Power + communication
• Based on RS-232

Controller

• Controls single door
    - Searches database and grants access
    - Sends logs to the server
• (optional) Power over Ethernet
• ARM Cortex M0 MCU
• Programmed in C (+ ChibiOS)

Server ↔ Controller

• Utilizes existing network
• Power over Ethernet
• UDP-based communication protocol
• Encrypted communication

Server

• "One server to rule them all"
• Manages access database
• Distributes access database to doors
• Provides support functions for embedded devices (logs, firmware upgrades)
  

What advantages does it have over the old system?

Price

Open source &

Open hardware

Easy to setup and maintain

Future-proof