--- title: "COAP messages on W5500 built for Nucleo-L476RG" url: "https://maker.wiznet.io/Aimee0/projects/coap-messages-on-w5500-built-for-nucleo-l476rg/" markdown_url: "https://maker.wiznet.io/Aimee0/projects/coap-messages-on-w5500-built-for-nucleo-l476rg/md" type: "UCC: User Created Content" author: "Aimee" author_url: "https://maker.wiznet.io/Aimee0/" original_author: "Aimee" original_url: "https://os.mbed.com/users/sgnezdov/code/coap-example//file/b56863927244/" published: "2024-01-02" language: "en" hardware: ["WIZnet W5500"] likes: 0 views: 371 comments: 0 source: "WIZnet Makers (https://maker.wiznet.io/)" --- # COAP messages on W5500 built for Nucleo-L476RG > This project is a project to send and receive COAP messages using W5500 over Nucleo-L476RG. Original author: Aimee (source: https://os.mbed.com/users/sgnezdov/code/coap-example//file/b56863927244/) ## Components - **WIZnet W5500** x 1 ([docs](https://docs.wiznet.io/Product/Chip/Ethernet/W5500)) WIZnet parts: W5500 ([Datasheet](https://docs.wiznet.io/Product/Chip/Ethernet/W5500/datasheet?utm_source=maker&utm_medium=project&utm_campaign=w5500), [product hub](https://maker.wiznet.io/products/w5500/)) ## Documents and links - [coap-example](https://os.mbed.com/users/sgnezdov/code/coap-example//file/b56863927244/) (code) ## Article This project is to send and receive COAP messages using W5500 over Nucleo-L476RG. **What is COAP** COAP is a lightweight protocol designed primarily to support efficient communication between IoT devices and devices with limited resources, such as various sensors. **COAP vs MQTT** | | COAP | MQTT | | --- | --- | --- | | Purpose | It is primarily designed for communication between constrained devices. | It is primarily designed for communication between many devices. | | Protocol format | Designed based on the RESTful architecture, it has a request and response form similar to HTTP. | It is a message-driven protocol that exchanges messages between brokers and clients. | | Communication | It uses a request-response model, in which the client sends the request and the server responds. | It is based on the Publish-Subscribe model, where devices can subscribe to specific topics to receive messages or publish messages to specific topics. | | Reliability and Connection Management | Primarily uses UDP, offering optional extensions for reliability. It is an unconnected protocol because it is UDP based. | Primarily uses TCP, providing reliable connections and message delivery. | **Project Description** OS : mbed-OS mbed-coap library : W5500 interface : #main.cpp ```plaintext ...... int main() { printf("Easy connect...\n"); NetworkInterface *network = easy_connect(true); if (!network) { printf("Cannot connect to the network, see serial output"); return 1; } printf("Connected to the network. Opening a socket...\n"); // Open a socket on the network interface socket.open(network); // Initialize the CoAP protocol handle, pointing to local implementations on malloc/free/tx/rx functions coapHandle = sn_coap_protocol_init(&coap_malloc, &coap_free, &coap_tx_cb, &coap_rx_cb); // UDPSocket::recvfrom is blocking, so run it in a separate RTOS thread recvfromThread.start(&recvfromMain); // Path to the resource we want to retrieve const char* coap_uri_path = "/test"; // See ns_coap_header.h sn_coap_hdr_s *coap_res_ptr = (sn_coap_hdr_s*)calloc(sizeof(sn_coap_hdr_s), 1); coap_res_ptr->uri_path_ptr = (uint8_t*)coap_uri_path; // Path coap_res_ptr->uri_path_len = strlen(coap_uri_path); coap_res_ptr->msg_code = COAP_MSG_CODE_REQUEST_GET; // CoAP method coap_res_ptr->content_format = COAP_CT_TEXT_PLAIN; // CoAP content type coap_res_ptr->payload_len = 0; // Body length coap_res_ptr->payload_ptr = 0; // Body pointer coap_res_ptr->options_list_ptr = 0; // Optional: options list // Message ID is used to track request->response patterns, because we're using UDP (so everything is unconfirmed). // See the receive code to verify that we get the same message ID back coap_res_ptr->msg_id = 7; // Calculate the CoAP message size, allocate the memory and build the message uint16_t message_len = sn_coap_builder_calc_needed_packet_data_size(coap_res_ptr); printf("Calculated message length: %d bytes\n", message_len); uint8_t* message_ptr = (uint8_t*)malloc(message_len); sn_coap_builder(message_ptr, coap_res_ptr); // Uncomment to see the raw buffer that will be sent... // printf("Message is: "); // for (size_t ix = 0; ix < message_len; ix++) { // printf("%02x ", message_ptr[ix]); // } // printf("\n"); int scount = socket.sendto("i-ce.itron.cloud", 5683, message_ptr, message_len); printf("Sent %d bytes to coap://i-ce.itron.cloud:5683\n", scount); free(coap_res_ptr); free(message_ptr); Thread::wait(osWaitForever); } ``` 1. Network initialization 2. open socket 3. COAP protocol init 4. COAP message recv thread start 5. COAP message builder run 6. send COAP message to i-ce.itron.cloud server's 5685 port #easy_connect.h ```plaintext ...... #define ETHERNET 1 #define WIFI_ESP8266 0 #define MESH_LOWPAN_ND 0 #define MESH_THREAD 0 #define WIFI_ODIN 0 #define WIFI_REALTEK 0 ...... NetworkInterface* easy_connect(bool log_messages = false) { NetworkInterface* network_interface = 0; int connect_success = -1; /// This should be removed once mbedOS supports proper dual-stack #if defined (MESH) || (MBED_CONF_LWIP_IPV6_ENABLED==true) printf("[EasyConnect] IPv6 mode\n"); #else printf("[EasyConnect] IPv4 mode\n"); #endif #if MBED_CONF_APP_NETWORK_INTERFACE == WIFI_ESP8266 ... #elif MBED_CONF_APP_NETWORK_INTERFACE == WIFI_ODIN ... #elif MBED_CONF_APP_NETWORK_INTERFACE == WIFI_REALTEK ... #elif MBED_CONF_APP_NETWORK_INTERFACE == ETHERNET if (log_messages) { printf("[EasyConnect] Ethernet...\n"); } spi.format(32, 0); spi.frequency(100000); printf("Wait for SPI...\r\n"); wait(1); printf("Network Setting DHCP\r\n"); uint8_t mac_addr[6] = {0x00, 0x08, 0xdc, 0x45, 0x56, 0x67}; printf("Init with MAC address\n"); eth.init(mac_addr); int timeout_ms = 15*1000; int err = dhcp.setup(ð, mac_addr, timeout_ms); if (err == (-1)) { printf("Timeout.\n"); return NULL; } printf("DHCP completed\n"); printf("Connected, IP: %d.%d.%d.%d\r\n", dhcp.yiaddr[0], dhcp.yiaddr[1], dhcp.yiaddr[2], dhcp.yiaddr[3]); char ip[24], gateway[24], netmask[24], dnsaddr[24]; sprintf(ip, "%d.%d.%d.%d", dhcp.yiaddr[0], dhcp.yiaddr[1], dhcp.yiaddr[2], dhcp.yiaddr[3]); sprintf(gateway, "%d.%d.%d.%d", dhcp.gateway[0], dhcp.gateway[1], dhcp.gateway[2], dhcp.gateway[3]); sprintf(netmask, "%d.%d.%d.%d", dhcp.netmask[0], dhcp.netmask[1], dhcp.netmask[2], dhcp.netmask[3]); sprintf(dnsaddr, "%d.%d.%d.%d", dhcp.dnsaddr[0], dhcp.dnsaddr[1], dhcp.dnsaddr[2], dhcp.dnsaddr[3]); eth.init(ip, netmask, gateway); dns.setup(ð); dns.set_server(dnsaddr); bool isOK = dns.lookup("coap.me"); if (isOK) { printf("is ok\n"); uint32_t hIP = dns.get_ip(); printf("coap.me IP: %u\n", hIP); } else { printf("coap.me IP is not ok\n"); } const SocketAddress dns_sa = SocketAddress((const void *)&dhcp.dnsaddr[0], NSAPI_IPv4, 53); nsapi_error_t nsErr = nsapi_dns_add_server(dns_sa); if (nsErr) { printf("[EasyConnect] error adding DNS entry: %d\n", nsErr); } printf("[EasyConnect] DNS IP: %s\n", dns_sa.get_ip_address()); SocketAddress coap_sa; nsErr = nsapi_dns_query(ð, "coap.me", &coap_sa, NSAPI_IPv4); if (nsErr) { printf("[EasyConnect] error resolving coap.me: %d\n", nsErr); } if (log_messages) { printf("[EasyConnect] Using Ethernet\n"); } network_interface = ð connect_success = eth.connect(); #endif #ifdef MESH ... #endif if(connect_success == 0) { if (log_messages) { printf("[EasyConnect] Connected to Network successfully\n"); print_MAC(network_interface, log_messages); } } else { if (log_messages) { print_MAC(network_interface, log_messages); printf("[EasyConnect] Connection to Network Failed %d!\n", connect_success); } return NULL; } const char *ip_addr = network_interface->get_ip_address(); if (ip_addr == NULL) { if (log_messages) { printf("[EasyConnect] ERROR - No IP address\n"); } return NULL; } if (log_messages) { printf("[EasyConnect] IP address %s\n", ip_addr); } return network_interface; } ``` Setting up SPI interface and network connectivity to use W5500. --- Source: https://maker.wiznet.io/Aimee0/projects/coap-messages-on-w5500-built-for-nucleo-l476rg/