--- title: "10. MicroPython development for W5100S/W5500+RP2040＜MQTT example＞" url: "https://maker.wiznet.io/ronpang/projects/10-micropython-development-for-w5100s-w5500-rp2040mqtt-example/" markdown_url: "https://maker.wiznet.io/ronpang/projects/10-micropython-development-for-w5100s-w5500-rp2040mqtt-example/md" type: "UCC: User Created Content" author: "WIZnet HK" author_url: "https://blog.csdn.net/WIZnet2012/article/details/135085014?spm=1001.2014.3001.5502" editor: "WIZnet" editor_url: "https://maker.wiznet.io/" original_author: "WIZnet HK" original_url: "https://blog.csdn.net/WIZnet2012/article/details/135085014?spm=1001.2014.3001.5502" published: "2024-01-03" language: "en" hardware: ["WIZnet W5100S-EVB-Pico", "WIZnet W5500-EVB-Pico"] likes: 0 views: 795 comments: 0 source: "WIZnet Makers (https://maker.wiznet.io/)" --- # 10. MicroPython development for W5100S/W5500+RP2040＜MQTT example＞ > 10. MicroPython development for W5100S/W5500+RP2040＜MQTT example＞ Original author: WIZnet HK (source: https://blog.csdn.net/WIZnet2012/article/details/135085014?spm=1001.2014.3001.5502) ## Components - **WIZnet W5100S-EVB-Pico** x 1 ([docs](https://docs.wiznet.io/Product/Chip/Ethernet/W5100S/w5100s-evb-pico)) - **WIZnet W5500-EVB-Pico** x 1 ([docs](https://docs.wiznet.io/Product/Chip/Ethernet/W5500/w5500-evb-pico)) ## Documents and links - [Code for this article](https://gitee.com/wiznet-hk/W5100S_W5500_Micro_Python) (code) - [YouTube demo](https://youtu.be/LiHdFJL2nVA) ## Article ### 1 Introduction In this era of smart hardware and the Internet of Things, MicroPython and Raspberry Pi PICO are leading the new trend of embedded development with their unique advantages. MicroPython, as a streamlined and optimized Python 3 language, provides efficient development and easy debugging for microcontrollers and embedded devices. When we combine it with the WIZnet W5100S/W5500 network module, the development potential of MicroPython and Raspberry Pi PICO is further amplified. Both modules have built-in TCP/IP protocol stacks, making it easier to implement network connections on embedded devices. Whether it is data transmission, remote control, or building IoT applications, they provide powerful support. In this chapter, we will take WIZnet W5100S as an example to use MicroPython development method to perform MQTT loopback communication example. ### 2. Related network information #### 2.1 Introduction MQTT is a standards-based message transfer protocol, or a set of rules for communication between machines. Smart sensors, wearables, and other Internet of Things (IoT) devices often need to send and receive data over resource-constrained, bandwidth-limited networks. These IoT devices use MQTT for data transmission as it is easy to implement and can transmit IoT data efficiently. MQTT supports message transmission from device to cloud and from cloud to device. ![](https://maker.wiznet.io/upload/ckeditor5/475731959%5F1704298090%2Epng) #### 2.2 Working principle MQTT communication includes the following four steps, of which the subscription and publishing steps may be multiple times: 1. **The client connects to the MQTT server:** The client establishes a connection with the MQTT server through the TCP/IP protocol. During the connection process, the client needs to provide the client identification (ClientId), as well as user name, password and other information to the server. If the connection is successful, the client and server will establish a session and start data transmission. 2. **Subscription to topics:** After establishing a connection, the client can subscribe to topics of interest in order to receive messages published on these topics. The subscription operation can be implemented through the SUBSCRIBE message in the MQTT protocol. The topic to be subscribed and the QoS (Quality of Service) level need to be specified in the message. The server will return a SUBACK message to indicate success or failure of the subscription. 3.** Publish messages: **After establishing a connection, the client can publish messages to the specified topic. The publishing operation can be implemented through the PUBLISH message in the MQTT protocol. The topic and message content to be published need to be specified in the message. The server will return a PUBACK message to indicate the success or failure of message publishing. 4.** Disconnect:** The client can actively disconnect from the MQTT server. Before disconnecting, the client needs to send a DISCONNECT message to the server. The server will return a DISCONNECT message, indicating that the connection was successfully disconnected. ![](https://maker.wiznet.io/upload/ckeditor5/475731959%5F1704298009%2Egif) #### 2.3 Advantages **Lightweight and efficient:** The implementation of MQTT on IoT devices requires minimal resources and therefore can be used even on small microcontrollers. For example, the smallest MQTT control message can be only two data bytes. MQTT message headers are also small, which optimizes network bandwidth. **Scalable: **MQTT implementation requires minimal code and consumes very little power in operation. The protocol also has built-in capabilities to support communication with a large number of IoT devices. Therefore, you can implement the MQTT protocol and connect with millions of such devices. **Reliable:** Many IoT devices connect via unreliable cellular networks with low bandwidth and high latency. MQTT has built-in capabilities that reduce the time it takes for IoT devices to reconnect to the cloud. It also defines three different quality of service levels to ensure reliability for IoT use cases - at most once (0), at least once (1), and exactly once (2). **Security:** MQTT enables developers to easily encrypt messages and authenticate devices and users using modern authentication protocols such as OAuth, TLS1.3, customer-managed certificates, and more. **Good support: **Many languages ​​such as Python provide extensive support for MQTT protocol implementation. Therefore, developers can quickly implement it in any type of application with minimal coding. **Publish-Subscribe Pattern:** One-to-many communication can be easily achieved. ![](https://maker.wiznet.io/upload/ckeditor5/475731959%5F1704298157%2Ejpg) #### 2.4 Application **Internet of Things M2M communication, Internet of Things big data collection:** MQTT protocol can achieve efficient communication between devices and real-time collection of large-scale data. **Android message push, WEB message push:** MQTT protocol can be used to implement real-time message push on Android and Web platforms. **Smart hardware, smart furniture, smart appliances: **MQTT protocol can be used for the control and management of smart hardware, smart furniture, smart appliances and other equipment. **Internet of Vehicles communication, electric vehicle station pile collection:** In the field of Internet of Vehicles, the MQTT protocol can be used for communication between vehicles and infrastructure, as well as data collection at electric vehicle charging stations. **Smart cities, telemedicine, and distance education:** In the fields of smart city construction, telemedicine, and distance education, the MQTT protocol can achieve efficient communication between devices and real-time collection of large-scale data. **Electric power, oil and energy and other industry markets: **In the electric power, oil and energy and other industries, the MQTT protocol can be used for remote monitoring and data collection of equipment. In general, the MQTT protocol is widely used in the field of Internet of Things because of its lightweight, simple, open and easy-to-implement characteristics. ![](https://maker.wiznet.io/upload/ckeditor5/475731959%5F1704298348%2Ejpg) ### 3. WIZnet Ethernet chip **WIZnet mainstream hardware protocol stack Ethernet chip parameter comparison** | **Model** | **Embedded Core** | **Host I/F** | **TX/RX Buffer** | **HW Socket** | **Network Performance** | | --- | --- | --- | --- | --- | --- | | W5100S | TCP/IPv4， MAC & PHY | 8bit BUS, SPI | 16KB | 4 | Max 25Mbps | | W6100 | TCP/IPv4/IPv6, MAC & PHY | 8bit BUS, Fast SPI | 32KB | 8 | Max 25Mbps | | W5500 | TCP/IPv4, MAC & PHY | Fast SPI | 32KB | 8 | Max 15Mbps | W5100S/W6100 supports 8-bit data bus interface, and the network transmission speed will be better than W5500. W6100 supports IPV6 and is compatible with W5100S hardware. If users who already use W5100S need to support IPv6, they can be Pin to Pin compatible. W5500 has more Sockets and send and receive buffers than W5100S Compared with the software protocol stack, WIZnet's hardware protocol stack Ethernet chip has the following advantages: **Hardware TCP/IP protocol stack: **WIZnet's hardware protocol stack chip provides a hardware-implemented TCP/IP protocol stack. This hardware-implemented protocol stack has better performance and stability than software-implemented protocol stacks. **No additional embedded system software stack and memory resources required: **Since all Ethernet transmit and receive operations are handled by the independent Ethernet controller, no additional embedded system software stack and memory resources are required. **Resistant to network environment changes and DDoS attacks: **Compared with software TCP/IP protocol stacks that are susceptible to network environment changes and DDoS attacks, hardware protocol stack chips can provide more stable Ethernet performance. **Suitable for low-specification embedded systems: **Even in low-specification embedded systems, hardware protocol stack chips using WIZnet can show more efficient Internet application operating performance than high-specification systems using software TCP/IP protocol stacks. ![](https://maker.wiznet.io/upload/ckeditor5/475731959%5F1704298479%2Epng) ## **4. MQTT communication example explanation and use** #### 4.1 Program flow chart ![](https://maker.wiznet.io/upload/ckeditor5/475731959%5F1704300054%2Epng) #### 4.2 Test preparation **Software:** Thonny MQTTX **Hardware:** W5100S IO module + RP2040 Raspberry Pi Pico development board or WIZnet W5100S-EVB-Pico development board Micro USB interface data cable cable #### 4.3 Connection method Connect to PC USB port via data cable When using W5100S/W5500 IO module to connect to RP2040 RP2040 GPIO 16 <----> W5100S/W5500 MISO RP2040 GPIO 17 <----> W5100S/W5500 CS RP2040 GPIO 18 <----> W5100S/W5500 SCK RP2040 GPIO 19 <----> W5100S/W5500 MOSI RP2040 GPIO 20 <----> W5100S/W5500 RST Directly connect to the PC network port through a network cable (or: both the PC and the device are connected to the switch or router LAN port through a network cable) #### 4.4 Related code We open the mqtt.py file directly. Step one: You can see that SPI is initialized in the w5x00_init() function. And register the spi-related pins and reset pins into the library. The subsequent step is to activate the network and use DHCP to configure the network address information. When DHCP fails, configure the static network address information. When the configuration is not successful, the information about the network address-related registers will be printed out, which can help us better troubleshoot the problem. Step 2: Try to connect to the MQTT server. If the connection fails, enter the reset procedure. Step 3: Subscribe to the topic, bind the message callback function, and start the timer to keep alive. Step 4: Wait for the message to be received, and perform loopback processing if the message is received. > In addition, the umqttsimple.py library needs to be saved to the development board, otherwise it will cause running errors. ``` #mqtt.py file from umqttsimple import MQTTClient from usocket import socket from machine import Pin,SPI,Timer import network import time import json ​ #mqtt config mqtt_params = {} mqtt_params['url'] = 'test.mosquitto.org' mqtt_params['port'] = 1883 mqtt_params['clientid'] = 'W5100S' mqtt_params['pubtopic'] = '/W5100S/pub' mqtt_params['subtopic'] = '/W5100S/sub' mqtt_params['pubqos'] = 0 mqtt_params['subqos'] = 0 ​ timer_1s_count = 0 tim = Timer() client = None ​ """ W5x00 chip initialization. param: None returns: None ​ """ def w5x00_init(): spi=SPI(0,2_000_000, mosi=Pin(19),miso=Pin(16),sck=Pin(18)) nic = network.WIZNET5K(spi,Pin(17),Pin(20)) #spi,cs,reset pin nic.active(True) try: #DHCP print("\r\nConfiguring DHCP") nic.ifconfig('dhcp') except: #None DHCP print("\r\nDHCP fails, use static configuration") nic.ifconfig(('192.168.1.20','255.255.255.0','192.168.1.1','8.8.8.8'))#Set static network address information #Print network address information print("IP :",nic.ifconfig()[0]) print("Subnet Mask:",nic.ifconfig()[1]) print("Gateway :",nic.ifconfig()[2]) print("DNS :",nic.ifconfig()[3],"\r\n") #If there is no network connection, the register address information is printed while not nic.isconnected(): time.sleep(1) print(nic.regs()) ​ """ Subscribe to the topic message callback function. This function is entered when a message is received from a subscribed topic. param1: The topic on which the callback is triggered param2: Message content returns: None ​ """ def sub_cb(topic, msg): topic = topic.decode('utf-8') msg = msg.decode('utf-8') if topic == mqtt_params['subtopic']: global client print("\r\ntopic:",topic,"\r\nrecv:", msg) client.publish(mqtt_params['pubtopic'],msg,qos = mqtt_params['pubqos']) print('\r\ntopic:',mqtt_params['pubtopic'],'\r\nsend:',msg) """ Connect to the MQTT server. param: None returns: None ​ """ def mqtt_connect(): client = MQTTClient(mqtt_params['clientid'], mqtt_params['url'], mqtt_params['port'],keepalive=60) client.connect() print('Connected to %s MQTT Broker'%(mqtt_params['url'])) return client ​ """ Connection error handler. param: None returns: None ​ """ def reconnect(): print('Failed to connected to Broker. Reconnecting...') time.sleep(5) machine.reset() ​ """ 1-second timer callback function. param1: class timer returns: None ​ """ def tick(timer): global timer_1s_count global client timer_1s_count += 1 if timer_1s_count >= 30: timer_1s_count = 0 client.ping() ​ """ Subscribe to Topics. param: client object returns: None ​ """ def subscribe(client): client.set_callback(sub_cb) client.subscribe(mqtt_params['subtopic'],mqtt_params['subqos']) print('subscribed to %s'%mqtt_params['subtopic']) def main(): global client print("WIZnet chip MQTT example") w5x00_init() try: client = mqtt_connect() except OSError as e: reconnect() subscribe(client) tim.init(freq=1, callback=tick) while True: client.wait_msg() client.disconnect() ​ if __name__ == "__main__": main() ``` ``` #umqttsimple.py file import usocket as socket import ustruct as struct from ubinascii import hexlify ​ ​ class MQTTException(Exception): pass ​ ​ class MQTTClient: def __init__( self, client_id, server, port=0, user=None, password=None, keepalive=0, ssl=False, ssl_params={}, ): if port == 0: port = 8883 if ssl else 1883 self.client_id = client_id self.sock = None self.server = server self.port = port self.ssl = ssl self.ssl_params = ssl_params self.pid = 0 self.cb = None self.user = user self.pswd = password self.keepalive = keepalive self.lw_topic = None self.lw_msg = None self.lw_qos = 0 self.lw_retain = False ​ def _send_str(self, s): self.sock.write(struct.pack("!H", len(s))) self.sock.write(s) ​ def _recv_len(self): n = 0 sh = 0 while 1: b = self.sock.read(1)[0] n |= (b & 0x7F) << sh if not b & 0x80: return n sh += 7 ​ def set_callback(self, f): self.cb = f ​ def set_last_will(self, topic, msg, retain=False, qos=0): assert 0 <= qos <= 2 assert topic self.lw_topic = topic self.lw_msg = msg self.lw_qos = qos self.lw_retain = retain ​ def connect(self, clean_session=True): self.sock = socket.socket() addr = socket.getaddrinfo(self.server, self.port)[0][-1] self.sock.connect(addr) if self.ssl: import ussl ​ self.sock = ussl.wrap_socket(self.sock, **self.ssl_params) premsg = bytearray(b"\x10\0\0\0\0\0") msg = bytearray(b"\x04MQTT\x04\x02\0\0") ​ sz = 10 + 2 + len(self.client_id) msg[6] = clean_session << 1 if self.user is not None: sz += 2 + len(self.user) + 2 + len(self.pswd) msg[6] |= 0xC0 if self.keepalive: assert self.keepalive < 65536 msg[7] |= self.keepalive >> 8 msg[8] |= self.keepalive & 0x00FF if self.lw_topic: sz += 2 + len(self.lw_topic) + 2 + len(self.lw_msg) msg[6] |= 0x4 | (self.lw_qos & 0x1) << 3 | (self.lw_qos & 0x2) << 3 msg[6] |= self.lw_retain << 5 ​ i = 1 while sz > 0x7F: premsg[i] = (sz & 0x7F) | 0x80 sz >>= 7 i += 1 premsg[i] = sz ​ self.sock.write(premsg, i + 2) self.sock.write(msg) # print(hex(len(msg)), hexlify(msg, ":")) self._send_str(self.client_id) if self.lw_topic: self._send_str(self.lw_topic) self._send_str(self.lw_msg) if self.user is not None: self._send_str(self.user) self._send_str(self.pswd) resp = self.sock.read(4) assert resp[0] == 0x20 and resp[1] == 0x02 if resp[3] != 0: raise MQTTException(resp[3]) return resp[2] & 1 ​ def disconnect(self): self.sock.write(b"\xe0\0") self.sock.close() ​ def ping(self): self.sock.write(b"\xc0\0") ​ def publish(self, topic, msg, retain=False, qos=0): pkt = bytearray(b"\x30\0\0\0") pkt[0] |= qos << 1 | retain sz = 2 + len(topic) + len(msg) if qos > 0: sz += 2 assert sz < 2097152 i = 1 while sz > 0x7F: pkt[i] = (sz & 0x7F) | 0x80 sz >>= 7 i += 1 pkt[i] = sz # print(hex(len(pkt)), hexlify(pkt, ":")) self.sock.write(pkt, i + 1) self._send_str(topic) if qos > 0: self.pid += 1 pid = self.pid struct.pack_into("!H", pkt, 0, pid) self.sock.write(pkt, 2) self.sock.write(msg) if qos == 1: while 1: op = self.wait_msg() if op == 0x40: sz = self.sock.read(1) assert sz == b"\x02" rcv_pid = self.sock.read(2) rcv_pid = rcv_pid[0] << 8 | rcv_pid[1] if pid == rcv_pid: return elif qos == 2: assert 0 ​ def subscribe(self, topic, qos=0): assert self.cb is not None, "Subscribe callback is not set" pkt = bytearray(b"\x82\0\0\0") self.pid += 1 struct.pack_into("!BH", pkt, 1, 2 + 2 + len(topic) + 1, self.pid) # print(hex(len(pkt)), hexlify(pkt, ":")) self.sock.write(pkt) self._send_str(topic) self.sock.write(qos.to_bytes(1, "little")) while 1: op = self.wait_msg() if op == 0x90: resp = self.sock.read(4) # print(resp) assert resp[1] == pkt[2] and resp[2] == pkt[3] if resp[3] == 0x80: raise MQTTException(resp[3]) return ​ # Wait for a single incoming MQTT message and process it. # Subscribed messages are delivered to a callback previously # set by .set_callback() method. Other (internal) MQTT # messages processed internally. def wait_msg(self): res = self.sock.read(1) # self.sock.setblocking(True) if res is None: return None if res == b"": raise OSError(-1) if res == b"\xd0": # PINGRESP sz = self.sock.read(1)[0] assert sz == 0 return None op = res[0] if op & 0xF0 != 0x30: return op sz = self._recv_len() topic_len = self.sock.read(2) topic_len = (topic_len[0] << 8) | topic_len[1] topic = self.sock.read(topic_len) sz -= topic_len + 2 if op & 6: pid = self.sock.read(2) pid = pid[0] << 8 | pid[1] sz -= 2 msg = self.sock.read(sz) self.cb(topic, msg) if op & 6 == 2: pkt = bytearray(b"\x40\x02\0\0") struct.pack_into("!H", pkt, 2, pid) self.sock.write(pkt) elif op & 6 == 4: assert 0 return op ​ # Checks whether a pending message from server is available. # If not, returns immediately with None. Otherwise, does # the same processing as wait_msg. def check_msg(self): # self.sock.setblocking(False) return self.wait_msg() ``` #### 4.5 Burning Verification > To test the Ethernet examples, the development environment must be configured to use a Raspberry Pi Pico. Required development environment [Thonny](https://thonny.org/) If you must compile MicroPython, you must use a Linux or Unix environment. Step 1: Copy the program into Thonny and select the environment as Raspberry Pi Pico. Step 2: Save the umqttsimple.py library file to the development board. ![](https://maker.wiznet.io/upload/ckeditor5/475731959%5F1704300210%2Egif) Step 3: Run the program, open MQTTX, connect to the same server, then subscribe to the development board's publishing topic, and the publishing topic is the development board's subscription topic. Step 4: Send a message in MQTTX to observe the loopback test effect. > Note: Because MicroPython's print function enables stdout buffering, sometimes the content will not be printed out immediately. ![](https://maker.wiznet.io/upload/ckeditor5/475731959%5F1704300237%2Egif) ### 5. Precautions If you use WIZnet's W5500 to implement the examples in this chapter, you only need to burn the firmware of the W5500 and run the example program. --- Source: https://maker.wiznet.io/ronpang/projects/10-micropython-development-for-w5100s-w5500-rp2040mqtt-example/