wireless ROS_serial using NodeMCU

nodeMCU_esp8266/README.md

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+# [NodeMCU](https://en.wikipedia.org/wiki/NodeMCU)
+- Know more about NodeMCU : [Project Page](https://www.nodemcu.com/index_en.html), [Github](https://github.com/nodemcu/nodemcu-devkit)

nodeMCU_esp8266/nodeMCU_ROSserial_publisher/README.md

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+## NodeMCU Esp8266 ROS_serial Publisher
+Upload [sketch](https://www.arduino.cc/en/tutorial/sketch) to NodeMCU from [Arduino IDE](https://www.arduino.cc/en/main/software).
+Connect to wireless access point by ESP.
+
+Echo msgs published by `chatter`, run each in separate terminals
+```
+    $ roscore
+    $ rosrun rosserial_python serial_node.py tcp
+    $ rostopic echo /chatter
+```

nodeMCU_esp8266/nodeMCU_ROSserial_publisher/nodeMCU_ROSserial_publisher.ino

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+#include <ESP8266WiFi.h>
+#include <ros.h>
+#include <std_msgs/String.h>
+
+/*  ESP AP Config.  */
+#ifndef APSSID
+#define APSSID "ESP_AP"
+#define APPSK  "ROSserial@nodeMCU"
+#endif
+
+const char *ssid = APSSID;
+const char *password = APPSK;
+
+/*  ROS  */
+IPAddress server(192,168,4,2);
+const uint16_t serverPort = 11411;
+
+ros::NodeHandle nh;
+std_msgs::String str_msg;
+ros::Publisher chatter("chatter", &str_msg);
+
+char firstMsg[5] = "Hey,"; bool recievedFirstMsg = false;
+char msgtxt[19] = "Message Recieved !";
+
+void setup() {
+  ESP.eraseConfig();
+  WiFi.disconnect(true);
+  WiFi.mode(WIFI_AP);
+  WiFi.softAP(ssid, password);
+  delay(1000);
+
+  nh.getHardware()->setConnection(server, serverPort);
+  nh.initNode();
+  nh.advertise(chatter);
+}
+
+void loop() {
+  if (nh.connected()) {
+    if(!recievedFirstMsg){
+      str_msg.data = firstMsg;
+      chatter.publish( &str_msg );
+      recievedFirstMsg = true;
+    }
+    str_msg.data = msgtxt;
+    chatter.publish( &str_msg );
+  } else {
+    // Don't publish unless connected..
+    recievedFirstMsg = false;
+  }
+  nh.spinOnce();
+  delay(1000);
+}

nodeMCU_esp8266/nodeMCU_ROSserial_subscriber/README.md

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+## NodeMCU Esp8266 ROS_serial Subscriber
+Upload [sketch](https://www.arduino.cc/en/tutorial/sketch) to NodeMCU from [Arduino IDE](https://www.arduino.cc/en/main/software) and open [Serial Monitor](https://www.arduino.cc/en/guide/environment#toc12).
+Connect to wireless access point by ESP.
+
+Publish msgs to `chatter_`, run each in separate terminals
+```
+    $ roscore
+    $ rosrun rosserial_python serial_node.py tcp
+    $ rostopic pub /chatter_ std_msgs/String "data: '<your msg here>'" --once
+```

nodeMCU_esp8266/nodeMCU_ROSserial_subscriber/nodeMCU_ROSserial_subscriber.ino

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+#include <ESP8266WiFi.h>
+#include <ros.h>
+#include <std_msgs/String.h>
+
+/*  ESP AP Config.  */
+#ifndef APSSID
+#define APSSID "ESP_AP"
+#define APPSK  "ROSserial@nodeMCU"
+#endif
+
+const char *ssid = APSSID;
+const char *password = APPSK;
+
+/*  ROS  */
+IPAddress server(192,168,4,2);
+const uint16_t serverPort = 11411;
+
+ros::NodeHandle nh;
+
+void messageCb(const std_msgs::String& str_msg){
+  String txt;
+  txt = str_msg.data;
+  Serial.println(txt);
+  int blinkCount = txt.length();
+  for(int i=1;i<=blinkCount;i++){
+    digitalWrite(LED_BUILTIN, HIGH-digitalRead(LED_BUILTIN));
+    delay(200);
+    digitalWrite(LED_BUILTIN, HIGH-digitalRead(LED_BUILTIN));
+    delay(200);
+  }
+}
+
+ros::Subscriber<std_msgs::String> sub("chatter_", &messageCb);
+
+void setup() {
+  ESP.eraseConfig();
+  WiFi.disconnect(true);
+  WiFi.mode(WIFI_AP);
+  WiFi.softAP(ssid, password);
+  delay(1000);
+
+  Serial.begin(9600);
+  pinMode(LED_BUILTIN,OUTPUT);
+
+  nh.getHardware()->setConnection(server, serverPort);
+  nh.initNode();
+  nh.subscribe(sub);
+}
+
+void loop() {
+  nh.spinOnce();
+  delay(1);
+}