--- title: "Setting Up UDP Multicast on W55RP20-EVB-PICO !" url: "https://maker.wiznet.io/Grace_Koo/projects/setting-up-udp-multicast-on-w55rp20-evb-pico-/" markdown_url: "https://maker.wiznet.io/Grace_Koo/projects/setting-up-udp-multicast-on-w55rp20-evb-pico-/md" type: "WCC: WIZnet Created Content" author: "Grace" author_url: "https://maker.wiznet.io/Grace_Koo/" original_author: "Grace Koo" published: "2024-12-12" language: "en" tags: ["W55RP20", "C/C++"] hardware: ["WIZnet W55RP20-EVB-Pico"] likes: 0 views: 2837 comments: 0 source: "WIZnet Makers (https://maker.wiznet.io/)" --- # Setting Up UDP Multicast on W55RP20-EVB-PICO ! > Setting Up UDP Multicast on W55RP20-EVB-PICO Original author: Grace Koo ## Components - **WIZnet W55RP20-EVB-Pico** x 1 ([docs](https://wiznet.io/products/powered-by-raspberry-pi/w55rp20-evb-pico)) ## Documents and links - [UDP multicast receiver](https://github.com/WIZnet-ioNIC/WIZnet-PICO-C/tree/main/examples/udp_multicast/udp_multicast_receiver) (code) ## Article UDP Multicast is a communication method that sends a single data packet to multiple receivers in a **multicast group**, using the network more efficiently than unicast or broadcast. - **Key Features:** 1. Efficient data distribution to multiple receivers. 2. No acknowledgment or retransmission (best effort). - **Common Use Cases:** 1. **Streaming Media:** Live video or audio broadcasting (e.g., IPTV). 2. **Gaming:** Real-time multiplayer game updates. 3. **Financial Systems:** Market data distribution. 4. **IoT Systems:** Device synchronization or firmware updates. 5. **Disaster Alert Systems:** Emergency notifications to multiple devices - **IPv4 Multicast Address Range : 224.0.0.0 ~ 239.255.255.255** This range is reserved for multicast communication and can be divided as follows: 1. **224.0.0.0 ~ 224.0.0.255**: **Local Network Multicast** Limited to the same subnet and does not traverse routers. 2. **239.0.0.0 ~ 239.255.255.255**: **Organization-specific Multicast** Used within private networks and can be configured like unicast addresses. #### Set up In this WCC, the **W55RP20-EVB-Pico** will function as the UDP multicast sender, so several socket configurations will be made. The receivers used include the **W5500-EVB-Pico**, **W5100S-EVB-Pico**, **W5500-EVB-Pico2**, and a **smartphone**. Additionally, since the multicast will be performed within the local network, the **TTL** is set to 1, ```c setSn_TTL(SOCKET_ID, 1); // set TTL (1 : local) ``` and the address is configured in the **224.0.0.1** range. ```c static uint8_t multicast_ip[4] = {224, 0, 0, 6}; // multicast ip address static uint16_t multicast_port = 29999; // multicast port ``` The multicast IP and port configured are set as the destination as follows. ```c setSn_DIPR(SOCKET_ID, multicast_ip); // destination IP 설정 setSn_DPORT(SOCKET_ID, multicast_port); // destination port 설정 ``` Multicast differs from standard ARP(Address Resolution Protocol) usage in that a specific IP address is shared by multiple receivers. Since multicast IP addresses are directly converted to MAC addresses, ARP is not required. Therefore, the MAC address is converted as follows ```c uint8_t multicast_mac[6] = { 0x01, 0x00, 0x5e, // First 3 bytes of the multicast MAC address multicast_ip[2] & 0x7f, // Last 23 bits of the IP address(first 7 bits of 224~239 : 1) multicast_ip[3], // Last 2 bytes of the IP address 0x00 // Remaining byte is set to 0 }; ``` and configured accordingly. ```c // Set the MAC address (DHAR: Socket n Destination Hardware Address Register) setSn_DHAR(SOCKET_ID, multicast_mac); // Skip ARP (Address Resolution Protocol) and directly set the MAC address setSn_CR(SOCKET_ID, Sn_CR_SEND_MAC); ``` The execution screen of the sender is as follows. When a rising edge is detected on a specific GPIO, the message is sent. ![](https://maker.wiznet.io/upload/ckeditor5/223655954%5F1734002233%2EPNG) The UDP multicast receiver was implemented with reference to the code below, and the smartphone was connected to the same Wi-Fi network, using the tester app for testing. > The following screen shows the receiver's display. ![](https://maker.wiznet.io/upload/ckeditor5/223655954%5F1734012425%2EPNG) The video showing both the sender and receivers together is as follows. [Embedded media](https://www.youtube.com/embed/PluWpFneIqU) ```c // UDP multicast sender #include #include "port_common.h" #include "wizchip_conf.h" #include "w5x00_spi.h" #include "w5x00_gpio_irq.h" #include "socket.h" #include "loopback.h" #include "multicast.h" #include "timer.h" /* Clock */ #define PLL_SYS_KHZ (133 * 1000) /* Buffer */ #define SOCKET_ID 1 // Socket number #define ETHERNET_BUF_MAX_SIZE (1024 * 2) // Send and receive cache size /* GPIO */ static void gpio_callback(void); /* Timer */ static void repeating_timer_callback(void); static time_t millis(void); wiz_NetInfo net_info = { .mac = {0x00, 0x08, 0xdc, 0x16, 0xed, 0x2e}, // Define MAC variables .ip = {192, 168, 11, 21}, // Define IP variables .sn = {255, 255, 255, 0}, // Define subnet variables .gw = {192, 168, 11, 1}, // Define gateway variables .dns = {168, 126, 63, 1}, // Define DNS variables .dhcp = NETINFO_STATIC}; // Define the DNCP mode static uint8_t ethernet_buf[ETHERNET_BUF_MAX_SIZE] = { 0, }; uint8_t data[] = "Warning! GPIO14 state is HIGH!"; static uint8_t multicast_ip[4] = {224, 0, 0, 6}; // multicast ip address static uint16_t multicast_port = 29999; // multicast port int flag = 0; volatile uint32_t prev_state = 0; volatile uint32_t current_state = 0; uint32_t start_ms = 0; static volatile uint32_t g_msec_cnt = 0; static void set_clock_khz(void); int main() { uint16_t local_port = 5000; uint8_t multicast_mac[6] = { 0x01, 0x00, 0x5e, // First 3 bytes of the multicast MAC address multicast_ip[2] & 0x7f, // Last 23 bits of the IP address(first 7 bits of 224~239 : 1) multicast_ip[3], // Last 2 bytes of the IP address 0x00 // Remaining byte is set to 0 }; gpio_init(14); gpio_init(15); gpio_set_dir(14, false); gpio_set_dir(15, true); gpio_put(15, 1); set_clock_khz(); /*mcu init*/ stdio_init_all(); // Initialize the main control peripheral. wizchip_spi_initialize(); wizchip_cris_initialize(); wizchip_reset(); wizchip_initialize(); // spi initialization wizchip_check(); wizchip_1ms_timer_initialize(repeating_timer_callback); wizchip_gpio_interrupt_initialize(SOCKET_ID, gpio_callback); network_initialize(net_info); print_network_information(net_info); // Read back the configuration information and print it setSn_DIPR(SOCKET_ID, multicast_ip); // Set destination IP setSn_DPORT(SOCKET_ID, multicast_port); // Set destination port setSn_DHAR(SOCKET_ID, multicast_mac); // Set the MAC address (DHAR: Socket n Destination Hardware Address Register) setSn_CR(SOCKET_ID, Sn_CR_SEND_MAC); // Skip ARP (Address Resolution Protocol) and directly set the MAC address setSn_TTL(SOCKET_ID, 1); // Set TTL (1 : local) // 소켓 초기화 if (socket(SOCKET_ID, Sn_MR_UDP, local_port, SF_MULTI_ENABLE) != SOCKET_ID) { printf("Failed to open socket\n"); } printf("Sends a message when GPIO14 detects a rising edge!\n"); while (1) { } } } static void set_clock_khz(void) { // set a system clock frequency in khz set_sys_clock_khz(PLL_SYS_KHZ, true); // configure the specified clock clock_configure( clk_peri, 0, // No glitchless mux CLOCKS_CLK_PERI_CTRL_AUXSRC_VALUE_CLKSRC_PLL_SYS, // System PLL on AUX mux PLL_SYS_KHZ * 1000, // Input frequency PLL_SYS_KHZ * 1000 // Output (must be same as no divider) ); } /* GPIO */ static void gpio_callback(void) { current_state = millis(); if((current_state - prev_state) > 500) { sendto(SOCKET_ID, data, sizeof(data), multicast_ip, multicast_port); printf("send!\n"); prev_state = current_state; } } /* Timer */ static void repeating_timer_callback(void) { g_msec_cnt++; } static time_t millis(void) { return g_msec_cnt; } ``` --- Source: https://maker.wiznet.io/Grace_Koo/projects/setting-up-udp-multicast-on-w55rp20-evb-pico-/