ESP8266和ROS收發消息讀取模擬量控制LED亮度

若是須要ESP8266和ROS通訊先閱讀以下博客：

• ESP8266和ROS調試一些問題彙總

• https://zhangrelay.blog.csdn.net/article/details/108762844

---

這裏測試環境melodic和noetic均可行。

源代碼以下：

#if (ARDUINO >= 100)
 #include <Arduino.h>
#else
 #include <WProgram.h>
#endif
#include <ESP8266WiFi.h>
#include <ros.h>
#include <std_msgs/String.h>
#include <std_msgs/Int16.h>
#include <std_msgs/Float64.h>
#include <Servo.h>
#include <rosserial_arduino/Adc.h>

//
// WiFi Definitions //
//
const char* ssid = "HUAWEI_WiFi";
const char* password = "cslgcslg";

IPAddress server(192, 168, 3, 153); // ip of your ROS server
IPAddress ip_address;
int status = WL_IDLE_STATUS;

WiFiClient client;

class WiFiHardware {

  public:
  WiFiHardware() {};

  void init() {
    // do your initialization here. this probably includes TCP server/client setup
    client.connect(server, 11411);
  }

  // read a byte from the serial port. -1 = failure
  int read() {
    // implement this method so that it reads a byte from the TCP connection and returns it
    //  you may return -1 is there is an error; for example if the TCP connection is not open
    return client.read();         //will return -1 when it will works
  }

  // write data to the connection to ROS
  void write(uint8_t* data, int length) {
    // implement this so that it takes the arguments and writes or prints them to the TCP connection
    for(int i=0; i<length; i++)
      client.write(data[i]);
  }

  // returns milliseconds since start of program
  unsigned long time() {
     return millis(); // easy; did this one for you
  }
};

Servo s;
int i;

void chatterCallback(const std_msgs::String& msg) {
  i = atoi(msg.data);
  s.write(i);
}


std_msgs::String str_msg;
rosserial_arduino::Adc adc_msg;
ros::Publisher chatter("chatter", &str_msg);
ros::Publisher p("adc", &adc_msg);
ros::Subscriber<std_msgs::String> sub("message", &chatterCallback);
ros::NodeHandle_<WiFiHardware> nh;
char hello[20] = "ESP8266 wifi alive!";


void setupWiFi()
{
  WiFi.begin(ssid, password);
  Serial.print("\nConnecting to "); Serial.println(ssid);
  uint8_t i = 0;
  while (WiFi.status() != WL_CONNECTED && i++ < 20) delay(500);
  if(i == 21){
    Serial.print("Could not connect to"); Serial.println(ssid);
    while(1) delay(500);
  }
  Serial.print("Ready! Use ");
  Serial.print(WiFi.localIP());
  Serial.println(" to access client");
}

int averageAnalog(int pin){
  int v=0;
  for(int i=0; i<2; i++) v+= analogRead(pin);
  return v/2;
}

void setup() {
  Serial.begin(115200);
  setupWiFi();
  delay(2000);
  s.attach(13);  // PWM pin
  nh.initNode();
  nh.advertise(chatter);
  nh.subscribe(sub);
  nh.advertise(p);
}

void loop() {
  str_msg.data = hello;
  chatter.publish( &str_msg );
  adc_msg.adc0 = averageAnalog( 0 );
  p.publish( &adc_msg );
  nh.spinOnce();
  delay( 10 );
}

簡單解釋一下，發佈節點chatter，adc，訂閱節點message。

1. message提取數值做爲PWM波送到13腳控制LED亮度（佔空比）；
2. adc採集模擬量繪製曲線；
3. chatter只用做發佈消息，告知主機鏈接成功。

---

使用以下命令啓動wemos D1和ROS：

• roscore
• rosrun rosserial_python serial_node.py tcp
• rostopic pub /message std_msgs/String "data: '10'"
• rostopic echo /adc
• rostopic echo /chatter

過程以下：

roscore

rosrun rosserial_python serial_node.py tcp

主題列表：

rostopic pub /message std_msgs/String "data: '10'"

使用rqt_graph查看全部節點狀態：

使用rosbag記錄ADC數據並使用plot查看曲線：

關閉全部節點，只留下roscore，使用rosbag play查看記錄數據：

 全部Arduino，stm32等單片機均可以藉助ROS實現物聯網硬件功能。

---

-Fin-