WROOM ESP32 Example Codes For IBM Watson IoT Platform

Abhishek Ghosh

By Abhishek Ghosh February 22, 2019 9:34 pm Updated on February 23, 2019

WROOM ESP32 Example Codes For IBM Watson IoT Platform

Here are few WROOM ESP32 example codes for IBM Watson IoT Platform so that anyone can get started with both of them the need of having huge experience. To follow this guide, one should have followed this guide on WROOM ESP32 dev boards to setup on Windows 10 PC. Next, one should read this kind of guide to open free account on IBM Cloud and create a new device ready to get connected with WROOM ESP32 dev board.

On IBM Watson IoT dashboard, you’ll get the Security option. Change the settings to TLS/HTTPS optional to make two of our sketches working. This is a mandatory step to avoid seeing failing authorization on the log. After you get used with a secure handshake, you probably will use strict TLS/HTTPS. Do not forget you did this change on security settings.

ESP32 Example Codes For IBM Cloud IoT Platform

There is no need of external hardware more than WROOM ESP32 dev board. Our one example has LED blink of on board LED. The effect and the board under question shown below :

WROOM ESP32 Example Codes For IBM Watson IoT Platform

We kept the codes on GitHub as repository. We will suggest using the code from there from the RAW file. We are providing some textual explanation here with code. A code may get wrongly copied chars from here.

For two of the codes, you need to install “PubSubClient” library from Arduino IDE’s manage library option. There are many detailed guides on the web about how to add library within Arduino IDE.

On Arduino’s serial monitor, you’ll see the output and also watch IBM Watson IoT’s particular device’s log. This sketches and testing for understanding whether the thing works. Later, you can create an application on IBM Cloud, connect it and do advanced graphing (we will not show that part on this guide).

Our first sketch simple-connect.ino starts with these, you’ll require to change ssid, password, ORG, DEVICE_TYPE, DEVICE_ID, TOKEN :

#include <WiFi.h>
#include <WiFiClient.h>
#include <PubSubClient.h> 

const char* ssid = "your hotspot";
const char* password = "abcdefgh";

#define ORG "abishek678"
#define DEVICE_TYPE "yourtype"
#define DEVICE_ID "your id"
#define TOKEN "your token"

...

1

2

3

4

5

6

7

8

9

10

11

12

13

#include <WiFi.h>

#include <WiFiClient.h>

#include <PubSubClient.h>

const char* ssid = "your hotspot";

const char* password = "abcdefgh";

#define ORG "abishek678"

#define DEVICE_TYPE "yourtype"

#define DEVICE_ID "your id"

#define TOKEN "your token"

...

Here is the complete code :

#include <WiFi.h>
#include <WiFiClient.h>
#include <PubSubClient.h> 

const char* ssid = "your hotspot";
const char* password = "abcdefgh";

#define ORG "abishek678"
#define DEVICE_TYPE "yourtype"
#define DEVICE_ID "your id"
#define TOKEN "your token"

char server[] = ORG ".messaging.internetofthings.ibmcloud.com";
char pubTopic[] = "iot-2/evt/status/fmt/json";
char subTopic[] = "iot-2/cmd/test/fmt/String";
char authMethod[] = "use-token-auth";
char token[] = TOKEN;
char clientId[] = "d:" ORG ":" DEVICE_TYPE ":" DEVICE_ID;

WiFiClient wifiClient;
PubSubClient client(server, 1883, NULL, wifiClient);

void setup() {
 Serial.begin(115200); delay(1); Serial.println();

 initWiFi();
}

void loop() {

 if (!!!client.connected()) {
   Serial.print("Reconnecting client to "); Serial.println(server);
   while (!!!client.connect(clientId, authMethod, token)) {
     Serial.print(".");
     delay(500);
   }
   Serial.println();
 }

 String payload = "{ \"d\" : {\"counter\":";
 payload += millis()/1000;
 payload += "}}";
 
Serial.print("Sending payload: "); Serial.println(payload);
 
 if (client.publish(pubTopic, (char*) payload.c_str())) {
   Serial.println("Publish ok");
 } else {
   Serial.println("Publish failed");
 }

 delay(3000);
}

void initWiFi() {
 Serial.print("Connecting to "); Serial.print(ssid);
 if (strcmp (WiFi.SSID().c_str(), ssid) != 0) {
   WiFi.begin(ssid, password);
 }
 while (WiFi.status() != WL_CONNECTED) {
   delay(500);
   Serial.print(".");
 } 
 Serial.println(""); Serial.print("WiFi connected, IP address: "); Serial.println(WiFi.localIP());
}

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

30

31

32

33

34

35

36

37

38

39

40

41

42

43

44

45

46

47

48

49

50

51

52

53

54

55

56

57

58

59

60

61

62

63

64

65

#include <WiFi.h>

#include <WiFiClient.h>

#include <PubSubClient.h>

const char* ssid = "your hotspot";

const char* password = "abcdefgh";

#define ORG "abishek678"

#define DEVICE_TYPE "yourtype"

#define DEVICE_ID "your id"

#define TOKEN "your token"

char server[] = ORG ".messaging.internetofthings.ibmcloud.com";

char pubTopic[] = "iot-2/evt/status/fmt/json";

char subTopic[] = "iot-2/cmd/test/fmt/String";

char authMethod[] = "use-token-auth";

char token[] = TOKEN;

char clientId[] = "d:" ORG ":" DEVICE_TYPE ":" DEVICE_ID;

WiFiClient wifiClient;

PubSubClient client(server, 1883, NULL, wifiClient);

void setup() {

Serial.begin(115200); delay(1); Serial.println();

initWiFi();

}

void loop() {

if (!!!client.connected()) {

Serial.print("Reconnecting client to "); Serial.println(server);

while (!!!client.connect(clientId, authMethod, token)) {

Serial.print(".");

delay(500);

}

Serial.println();

}

String payload = "{ \"d\" : {\"counter\":";

payload += millis()/1000;

payload += "}}";

Serial.print("Sending payload: "); Serial.println(payload);

if (client.publish(pubTopic, (char*) payload.c_str())) {

Serial.println("Publish ok");

} else {

Serial.println("Publish failed");

}

delay(3000);

}

void initWiFi() {

Serial.print("Connecting to "); Serial.print(ssid);

if (strcmp (WiFi.SSID().c_str(), ssid) != 0) {

WiFi.begin(ssid, password);

}

while (WiFi.status() != WL_CONNECTED) {

delay(500);

Serial.print(".");

}

Serial.println(""); Serial.print("WiFi connected, IP address: "); Serial.println(WiFi.localIP());

}

Our second sketch simple-https.ino starts with these, you’ll require to change ssid, password, ORG, DEVICE_TYPE, DEVICE_ID, TOKEN :

#include <WiFi.h>
#include <WiFiMulti.h>
#include <HTTPClient.h>
#include <base64.h>

#define USE_SERIAL Serial 

const char* ssid = "your hotspot";
const char* password = "abcdefgh";

#define ORG "abishek678"
#define DEVICE_TYPE "yourtype"
#define DEVICE_ID "your id"
#define TOKEN "your token"
#define EVENT "myEvent" 

...

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

#include <WiFi.h>

#include <WiFiMulti.h>

#include <HTTPClient.h>

#include <base64.h>

#define USE_SERIAL Serial

const char* ssid = "your hotspot";

const char* password = "abcdefgh";

#define ORG "abishek678"

#define DEVICE_TYPE "yourtype"

#define DEVICE_ID "your id"

#define TOKEN "your token"

#define EVENT "myEvent"

...

Here is the complete code :

#include <WiFi.h>
#include <WiFiMulti.h>
#include <HTTPClient.h>
#include <base64.h>

#define USE_SERIAL Serial 

const char* ssid = "your hotspot";
const char* password = "abcdefgh";

#define ORG "abishek678"
#define DEVICE_TYPE "yourtype"
#define DEVICE_ID "your id"
#define TOKEN "your token"
#define EVENT "myEvent" 

String urlPath = "/api/v0002/device/types/" DEVICE_TYPE "/devices/" DEVICE_ID "/events/" EVENT;
String urlHost = ORG ".messaging.internetofthings.ibmcloud.com";
int urlPort = 8883;
String authHeader;

void setup() {
  Serial.begin(115200); Serial.println(); 
  initWifi();
  Serial.println("View the published data on Watson at: "); 
  if (ORG == "quickstart") {
    Serial.println("https://quickstart.internetofthings.ibmcloud.com/#/device/" DEVICE_ID "/sensor/");
  } else {
    Serial.println("https://" ORG ".internetofthings.ibmcloud.com/dashboard/#/devices/browse/drilldown/" DEVICE_TYPE "/" DEVICE_ID);
  }  
  if (ORG == "quickstart") {
    authHeader = "";
  } else {
    authHeader = "Authorization: Basic " + base64::encode("use-token-auth:" TOKEN) + "\r\n";
  }  
}

void loop() {
  doWiFiClientSecure();
  delay(10000);
}

void doWiFiClientSecure() {
 WiFiClientSecure client;
 Serial.print("connect: "); Serial.println(urlHost);
 while ( ! client.connect(urlHost.c_str(), urlPort)) {
    Serial.print(".");
 }
 Serial.println("Connected");
 String postData = String("{  \"d\": {\"aMessage\": \"") + millis()/1000 + "\"}  }";
 String msg = "POST " + urlPath + " HTTP/1.1\r\n"
                "Host: " + urlHost + "\r\n"
                "" + authHeader + ""
                "Content-Type: application/json\r\n"
                "Content-Length: " + postData.length() + "\r\n"
                "\r\n" + postData;
                
 client.print(msg);
 Serial.print(msg);

 Serial.print("\n*** Request sent, receiving response...");
 while (!!!client.available()) {
    delay(50);
 Serial.print(".");
  }
  
Serial.println();
Serial.println("Got response");  
  while(client.available()){
  Serial.write(client.read());
  }
Serial.println(); Serial.println("closing connection");
  client.stop();
}

void initWifi() {
  Serial.print("Connecting to: "); Serial.print(WiFi.SSID());
  WiFi.mode(WIFI_STA);   
  WiFi.begin(ssid, password);  
  while (WiFi.status() != WL_CONNECTED) {
     delay(250);
     Serial.print(".");
  }
  
  Serial.println("");
  Serial.print("WiFi connected, IP address: "); Serial.println(WiFi.localIP());

}

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

30

31

32

33

34

35

36

37

38

39

40

41

42

43

44

45

46

47

48

49

50

51

52

53

54

55

56

57

58

59

60

61

62

63

64

65

66

67

68

69

70

71

72

73

74

75

76

77

78

79

80

81

82

83

84

85

86

87

88

#include <WiFi.h>

#include <WiFiMulti.h>

#include <HTTPClient.h>

#include <base64.h>

#define USE_SERIAL Serial

const char* ssid = "your hotspot";

const char* password = "abcdefgh";

#define ORG "abishek678"

#define DEVICE_TYPE "yourtype"

#define DEVICE_ID "your id"

#define TOKEN "your token"

#define EVENT "myEvent"

String urlPath = "/api/v0002/device/types/" DEVICE_TYPE "/devices/" DEVICE_ID "/events/" EVENT;

String urlHost = ORG ".messaging.internetofthings.ibmcloud.com";

int urlPort = 8883;

String authHeader;

void setup() {

Serial.begin(115200); Serial.println();

initWifi();

Serial.println("View the published data on Watson at: ");

if (ORG == "quickstart") {

Serial.println("https://quickstart.internetofthings.ibmcloud.com/#/device/" DEVICE_ID "/sensor/");

} else {

Serial.println("https://" ORG ".internetofthings.ibmcloud.com/dashboard/#/devices/browse/drilldown/" DEVICE_TYPE "/" DEVICE_ID);

}

if (ORG == "quickstart") {

authHeader = "";

} else {

authHeader = "Authorization: Basic " + base64::encode("use-token-auth:" TOKEN) + "\r\n";

}

void loop() {

doWiFiClientSecure();

delay(10000);

}

void doWiFiClientSecure() {

WiFiClientSecure client;

Serial.print("connect: "); Serial.println(urlHost);

while ( ! client.connect(urlHost.c_str(), urlPort)) {

Serial.print(".");

}

Serial.println("Connected");

String postData = String("{ \"d\": {\"aMessage\": \"") + millis()/1000 + "\"} }";

String msg = "POST " + urlPath + " HTTP/1.1\r\n"

"Host: " + urlHost + "\r\n"

"" + authHeader + ""

"Content-Type: application/json\r\n"

"Content-Length: " + postData.length() + "\r\n"

"\r\n" + postData;

client.print(msg);

Serial.print(msg);

Serial.print("\n*** Request sent, receiving response...");

while (!!!client.available()) {

delay(50);

Serial.print(".");

}

Serial.println();

Serial.println("Got response");

while(client.available()){

Serial.write(client.read());

}

Serial.println(); Serial.println("closing connection");

client.stop();

}

void initWifi() {

Serial.print("Connecting to: "); Serial.print(WiFi.SSID());

WiFi.mode(WIFI_STA);

WiFi.begin(ssid, password);

while (WiFi.status() != WL_CONNECTED) {

delay(250);

Serial.print(".");

}

Serial.println("");

Serial.print("WiFi connected, IP address: "); Serial.println(WiFi.localIP());

}

Our third sketch temperature.ino starts with these, you’ll require to change ssid, password, ORG, DEVICE_TYPE, DEVICE_ID, TOKEN :

#include <WiFi.h>
#include <WiFiClient.h>
#include <PubSubClient.h> 

// <------- CHANGE PARAMETERS BELOW THIS LINE ------------>

const char ledPin = 2;

const char* ssid = "YOUR-HOTSPOT-NAME";
const char* password = "YOUR-HOTSPOT-PASSWORD";

#define ORG "YOUR-ORG-NAME-ON-IBM-DASHBOARD"
#define DEVICE_TYPE "YOUR-SET-DEVICE-TYPE"
#define DEVICE_ID "YOUR-SET-DEVICE-ID"
#define TOKEN "YOUR-SET-TOKEN-OR-AUTOGENERATED-TOKEN"

// <------- CHANGE PARAMETERS ABOVE THIS LINE ------------>

char server[] = ORG ".messaging.internetofthings.ibmcloud.com";
char pubTopic[] = "iot-2/evt/status/fmt/json";
char subTopic[] = "iot-2/cmd/test/fmt/String";
char authMethod[] = "use-token-auth";
char token[] = TOKEN;
char clientId[] = "d:" ORG ":" DEVICE_TYPE ":" DEVICE_ID;


...

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

#include <WiFi.h>

#include <WiFiClient.h>

#include <PubSubClient.h>

// <------- CHANGE PARAMETERS BELOW THIS LINE ------------>

const char ledPin = 2;

const char* ssid = "YOUR-HOTSPOT-NAME";

const char* password = "YOUR-HOTSPOT-PASSWORD";

#define ORG "YOUR-ORG-NAME-ON-IBM-DASHBOARD"

#define DEVICE_TYPE "YOUR-SET-DEVICE-TYPE"

#define DEVICE_ID "YOUR-SET-DEVICE-ID"

#define TOKEN "YOUR-SET-TOKEN-OR-AUTOGENERATED-TOKEN"

// <------- CHANGE PARAMETERS ABOVE THIS LINE ------------>

char server[] = ORG ".messaging.internetofthings.ibmcloud.com";

char pubTopic[] = "iot-2/evt/status/fmt/json";

char subTopic[] = "iot-2/cmd/test/fmt/String";

char authMethod[] = "use-token-auth";

char token[] = TOKEN;

char clientId[] = "d:" ORG ":" DEVICE_TYPE ":" DEVICE_ID;

...

Here is the complete code :

#include <WiFi.h>
#include <WiFiClient.h>
#include <PubSubClient.h> 

// <------- CHANGE PARAMETERS BELOW THIS LINE ------------>

const char ledPin = 2;

const char* ssid = "YOUR-HOTSPOT-NAME";
const char* password = "YOUR-HOTSPOT-PASSWORD";

#define ORG "YOUR-ORG-NAME-ON-IBM-DASHBOARD"
#define DEVICE_TYPE "YOUR-SET-DEVICE-TYPE"
#define DEVICE_ID "YOUR-SET-DEVICE-ID"
#define TOKEN "YOUR-SET-TOKEN-OR-AUTOGENERATED-TOKEN"

// <------- CHANGE PARAMETERS ABOVE THIS LINE ------------>

char server[] = ORG ".messaging.internetofthings.ibmcloud.com";
char pubTopic[] = "iot-2/evt/status/fmt/json";
char subTopic[] = "iot-2/cmd/test/fmt/String";
char authMethod[] = "use-token-auth";
char token[] = TOKEN;
char clientId[] = "d:" ORG ":" DEVICE_TYPE ":" DEVICE_ID;

WiFiClient wifiClient;
PubSubClient client(server, 1883, NULL, wifiClient);

void receivedCallback(char* pubTopic, byte* payload, unsigned int length) {
  Serial.print("Message received: ");
  Serial.println(pubTopic);

  Serial.print("payload: ");
  for (int i = 0; i < length; i++) {
    Serial.print((char)payload[i]);
  }
  Serial.println();
  /* we got '1' -> on */}

void setup() {
    Serial.begin(115200);
    Serial.println();
    pinMode(ledPin, OUTPUT);
    Serial.print("Connecting to "); 
    Serial.print(ssid);
    WiFi.begin(ssid, password);
    while (WiFi.status() != WL_CONNECTED) {
      delay(500);
      Serial.print(".");
    } 
    Serial.println("");
    
    Serial.print("WiFi connected, IP address: "); 
    Serial.println(WiFi.localIP());

    if (!client.connected()) {
        Serial.print("Reconnecting client to ");
        Serial.println(server);
        while (!client.connect(clientId, authMethod, token)) {
            Serial.print(".");
            delay(500);
        }
        client.setCallback(receivedCallback);
        if (client.subscribe(subTopic)) {
            Serial.println("subscribe to cmd OK");
        } else {
            Serial.println("subscribe to cmd FAILED");
        }
        Serial.println("IBM Watson IoT connected");
    }
}

long lastMsg = 0;
long temperature = 0;

void loop() {
    client.loop();
    long now = millis();
    if (now - lastMsg > 3000) {
        lastMsg = now;
        temperature = random(0, 40);
        String payload = "{\"d\":{\"Name\":\"" DEVICE_ID "\"";
              payload += ",\"temperature\":";
              payload += temperature;
              payload += "}}";
        Serial.print("Sending payload: ");
        Serial.println(payload);

        if (client.publish(pubTopic, (char*) payload.c_str())) {
            Serial.println("Publish ok");
        digitalWrite(ledPin, HIGH);
        delay(1000);
        digitalWrite(ledPin, LOW);
        delay(1000);
        } else {
            Serial.println("Publish failed");
        }
    }
}

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

30

31

32

33

34

35

36

37

38

39

40

41

42

43

44

45

46

47

48

49

50

51

52

53

54

55

56

57

58

59

60

61

62

63

64

65

66

67

68

69

70

71

72

73

74

75

76

77

78

79

80

81

82

83

84

85

86

87

88

89

90

91

92

93

94

95

96

97

98

99

100

#include <WiFi.h>

#include <WiFiClient.h>

#include <PubSubClient.h>

// <------- CHANGE PARAMETERS BELOW THIS LINE ------------>

const char ledPin = 2;

const char* ssid = "YOUR-HOTSPOT-NAME";

const char* password = "YOUR-HOTSPOT-PASSWORD";

#define ORG "YOUR-ORG-NAME-ON-IBM-DASHBOARD"

#define DEVICE_TYPE "YOUR-SET-DEVICE-TYPE"

#define DEVICE_ID "YOUR-SET-DEVICE-ID"

#define TOKEN "YOUR-SET-TOKEN-OR-AUTOGENERATED-TOKEN"

// <------- CHANGE PARAMETERS ABOVE THIS LINE ------------>

char server[] = ORG ".messaging.internetofthings.ibmcloud.com";

char pubTopic[] = "iot-2/evt/status/fmt/json";

char subTopic[] = "iot-2/cmd/test/fmt/String";

char authMethod[] = "use-token-auth";

char token[] = TOKEN;

char clientId[] = "d:" ORG ":" DEVICE_TYPE ":" DEVICE_ID;

WiFiClient wifiClient;

PubSubClient client(server, 1883, NULL, wifiClient);

void receivedCallback(char* pubTopic, byte* payload, unsigned int length) {

Serial.print("Message received: ");

Serial.println(pubTopic);

Serial.print("payload: ");

for (int i = 0; i < length; i++) {

Serial.print((char)payload[i]);

}

Serial.println();

/* we got '1' -> on */

}

void setup() {

Serial.begin(115200);

Serial.println();

pinMode(ledPin, OUTPUT);

Serial.print("Connecting to ");

Serial.print(ssid);

WiFi.begin(ssid, password);

while (WiFi.status() != WL_CONNECTED) {

delay(500);

Serial.print(".");

}

Serial.println("");

Serial.print("WiFi connected, IP address: ");

Serial.println(WiFi.localIP());

if (!client.connected()) {

Serial.print("Reconnecting client to ");

Serial.println(server);

while (!client.connect(clientId, authMethod, token)) {

Serial.print(".");

delay(500);

}

client.setCallback(receivedCallback);

if (client.subscribe(subTopic)) {

Serial.println("subscribe to cmd OK");

} else {

Serial.println("subscribe to cmd FAILED");

}

Serial.println("IBM Watson IoT connected");

}

long lastMsg = 0;

long temperature = 0;

void loop() {

client.loop();

long now = millis();

if (now - lastMsg > 3000) {

lastMsg = now;

temperature = random(0, 40);

String payload = "{\"d\":{\"Name\":\"" DEVICE_ID "\"";

payload += ",\"temperature\":";

payload += temperature;

payload += "}}";

Serial.print("Sending payload: ");

Serial.println(payload);

if (client.publish(pubTopic, (char*) payload.c_str())) {

Serial.println("Publish ok");

digitalWrite(ledPin, HIGH);

delay(1000);

digitalWrite(ledPin, LOW);

delay(1000);

} else {

Serial.println("Publish failed");

}

Conclusion

Enough coding provided to get started. Next steps are creating own application on IBM cloud for data analysis (or some other work) :

https://console.bluemix.net/docs/services/IoT/GA_information_management/ga_im_device_twin.html#device_twins
https://www.ibm.com/support/knowledgecenter/SSQP8H/iot/overview/overview.html
https://www.ibm.com/support/knowledgecenter/SSQP8H/iot/developing/develop.html#real-time-analytics

1

2

3

https://console.bluemix.net/docs/services/IoT/GA_information_management/ga_im_device_twin.html#device_twins

https://www.ibm.com/support/knowledgecenter/SSQP8H/iot/overview/overview.html

https://www.ibm.com/support/knowledgecenter/SSQP8H/iot/developing/develop.html#real-time-analytics

Tagged With esp32 iot platforms , best iot platform for esp32 , define string esp32

Cookie	Duration	Description
cookielawinfo-checkbox-analytics	11 months	This cookie is set by GDPR Cookie Consent plugin. The cookie is used to store the user consent for the cookies in the category "Analytics".
cookielawinfo-checkbox-functional	11 months	The cookie is set by GDPR cookie consent to record the user consent for the cookies in the category "Functional".
cookielawinfo-checkbox-necessary	11 months	This cookie is set by GDPR Cookie Consent plugin. The cookies is used to store the user consent for the cookies in the category "Necessary".
cookielawinfo-checkbox-others	11 months	This cookie is set by GDPR Cookie Consent plugin. The cookie is used to store the user consent for the cookies in the category "Other.
cookielawinfo-checkbox-performance	11 months	This cookie is set by GDPR Cookie Consent plugin. The cookie is used to store the user consent for the cookies in the category "Performance".
viewed_cookie_policy	11 months	The cookie is set by the GDPR Cookie Consent plugin and is used to store whether or not user has consented to the use of cookies. It does not store any personal data.

About Abhishek Ghosh

Here’s what we’ve got for you which might like :

Take The Conversation Further ...

Get new posts by email:

ESP32 Example Codes For IBM Cloud IoT Platform

Conclusion

This Article Has Been Shared 575 Times!

About Abhishek Ghosh

Here’s what we’ve got for you which might like :

Articles Related to WROOM ESP32 Example Codes For IBM Watson IoT Platform

Take The Conversation Further ...

Get new posts by email: