XCSOURCE FT232RL | 3l3c7r1c pl4y6r0und

When I started layouting the PCB for my irrigation sensor I realized the advantages of a breakout board. They are handy for developing, sure. But they also bear the big advantage that you do not have to take care about repetitive tasks (such as pull-up resistors). Additionally they ease up layouting by adding two additional layers to your design. That simplifies the design and it also minimizes the footprint of the final PCB.

Size was the most important factor for me. It isn’t just a question of space, it is also a question of price (PCB cost ist based on cm²). Beside the pull up resistors for CH_PD, GPIO_0, GPIO_2 and RESET and the buttons to ground RESET and GPIO_0 (PROG) I have also foreseen a pin header for connecting my XCSOURCE FT232RL USB<->TTL. The voltage supply of the USB-TTL converter can be enabled or disabled with a jumper. Additionally I have foreseen solder jumpers CTS->REST and DTR->GPIO_0. I’ve not tried personally but some sources say that this connections make the manual buttons obsolete by handing over this task to the USB-TTL converter. Finally there is also a solder jumper to connect GPIO_16 and RESET (for wake up after deep sleep) and a capacitor as voltage stabilizer. Other boards like the Huzzah Board use a voltage converter for this but I have made good experience with the capacitor.

My followers on twitter know that it took several attempts before I got my final version ready (special thanks here to @ccxx72, @i_grr, @bdcatalin und @tzapulica for their help). I also faced some troubles with Fritzing but finally you can download my result at Github: https://github.com/Stromspielplatz/misc/tree/master/ESP8266%20ESP-12%20Breakout

ESP8266-ESP12 Breakout Board Circuit Diagram

In a first step I will make a prototype for my sensor board. Usually you build a prototype just on a breadboard. But I would like to use my prototype for some weeks to see how my sensors work and how much energy is needed. Therefore I use a prototype circuit board instead.

My shopping list for that:

Additionally I need:

A prototype circuit board
3 pcs. 10k Resistors (can be even bigger as long aa all 3 are equal)
1 electrolytic capacitor (>500uF)
1 Transisotr (e.g. BC547C)
1 3K3 Resistor
a pin header
a jumper
a soldering iron

I know that there a many statements about the right soldering iron in the internet but for me personally a cheap soldering station is more than enough. There is also a good desoldering pump coming with the station and every beginner will need it. If you have too much money then spend it in a quite good solder. As power supply I use a USB powerbank that I’ve received as a giveaway. You can also get one for less than 10€ (e.g. here)

I try to do not solder items directly when building a prototype. Therefore I use pin headers. The disadvantage is that the prototype is not that robust but the advantage is I can easily borrow some parts without taking the soldering iron.

The ESP8266 just takes 3.3V so I take the USB to TTL converter also as voltage converter. Be sure to put the jumper to 3.3V. To safe energy I will put my ESP in deep-sleep. To prevent my sensors taking power when they are not used I use a transistor to power them on only when needed. The ESP needs quite a high current when connecting to the WLAN. I use an electrolytic capacitor parallel to the voltage supply. Sizing of that is no rocket science, it should be somewhere between 400uF and 2200uF (6-10V). For programming the ESP the CH_PD Pin has to be put on ground. Some recommend a button for that but I prefer a jumper.

The manual for the ESP8266 says that for wake up from deep-sleep pin 16 has to be connected to CH_PD. Unfortunately for some reasons this is not working with mine. I use the RESET for the wakeup instead. This prevents using some options for wakeup but I don’t care for the prototype.

Der Prototyp in EAGLE — Prototype in EAGLE

It is a puzzle to place all the components on the board. I tried to save as much space because I had a small leftover to be used.

Meine Prototyen Platine — My final prototype

For programming my ESP I use the Arduio IDE. You have to install the ESP board in the IDE. Add in File->Properties->Additional Board Manager URLs: http://arduino.esp8266.com/stable/package_esp8266com_index.json Select Board „…“ > Board Manager… , choose esp8266 and press install. After that you can program the ESP like any other Arduino. For programming the jumper has to be set on starting the board. Sometimes the upload fails with some strange error messages. If this happens I simply restart the ESP and try it again. Remember to remove the jumper after uploading the software. Wake-up from deep-sleep is not working when the jumper ist set.

#include 

// WLAN Name und Password (PSK)
const char* ssid = "SSID";
const char* password = "PSK"; 
WiFiClient client;

// Server Adress of my raspberry
char server[] = "10.0.0.3";
int port = 80; //If you use a different port on your webserver adjust the no here

// Update Intervall
const unsigned long postingInterval = 1800L * 1000000L;

//DHT init
#include 
#define DHTPIN 4
#define DHTTYPE DHT11   // DHT 11 
DHT dht(DHTPIN, DHTTYPE,16);

// needed to avoid link error on ram check
extern "C" 
{
#include "user_interface.h"
}

void setup() {
  // Pin 12 powers the sensors
  pinMode(12, OUTPUT);
  digitalWrite(12, HIGH);
  // Serial interface for debugging
  Serial.begin(115200);
  Serial.println("WLAN Logger - Electric Playground");
  // start WIFI
  WiFi.mode(WIFI_STA);
  WiFiStart();
  // waiting
  delay(3000);
  //DHT init
  dht.begin();
  // ADC (Soil) init
  pinMode(A0, INPUT);
}

void loop() {
  // debug
  while (client.available()) {
    char c = client.read();
    Serial.write(c);
  }
  // read sensor values
  float hum = dht.readHumidity();
  float temp = dht.readTemperature();
  float soil = analogRead(A0);
  //Debug
  Serial.println("Humidity:"+String(hum,2)+"\tTemperature:"+String(temp,2)+"\tSoil:"+String(soil,2));
  //Send values
  httpRequest(hum,temp,soil);
  //power of sensors and go to deep sleep
  delay(500);
  digitalWrite(12, LOW);
  ESP.deepSleep(postingInterval, WAKE_NO_RFCAL); 
  delay(1000);
}


//Transmit data to webserver
void httpRequest(float h, float t, float s) {
  client.stop();
  delay(100);
  //build URL
  String url = "/newrecord.php?";
  url += "temp=";
  url += String(t,2);
  url += "&humidity=";
  url += String(h,2);
  url += "&soil=";
  url += String(s,2);
  // call URL
  if (client.connect(server, port)) {
    Serial.println("connecting...");
    client.print(String("GET ") + url + " HTTP/1.1\r\n" +
               "Host: " + server + "\r\n" + 
               "Connection: close\r\n\r\n");
    Serial.println("data submitted.");
    delay(10);
  
  } else {
    Serial.println("connection failed");
  }
}
// Establish WIFI connection
void WiFiStart()
{ 
  Serial.print("Connecting to ");
  Serial.println(ssid); 
  WiFi.begin(ssid, password);
  while (WiFi.status() != WL_CONNECTED) 
  {
    delay(500);
    Serial.print(".");
  }
  Serial.println("");
  Serial.println("WiFi connected");
  Serial.println(WiFi.localIP());
}

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#include

// WLAN Name und Password (PSK)

const char* ssid = "SSID";

const char* password = "PSK";

WiFiClient client;

// Server Adress of my raspberry

char server[] = "10.0.0.3";

int port = 80; //If you use a different port on your webserver adjust the no here

// Update Intervall

const unsigned long postingInterval = 1800L * 1000000L;

//DHT init

#include

#define DHTPIN 4

#define DHTTYPE DHT11 // DHT 11

DHT dht(DHTPIN, DHTTYPE,16);

// needed to avoid link error on ram check

extern "C"

{

#include "user_interface.h"

}

void setup() {

// Pin 12 powers the sensors

pinMode(12, OUTPUT);

digitalWrite(12, HIGH);

// Serial interface for debugging

Serial.begin(115200);

Serial.println("WLAN Logger - Electric Playground");

// start WIFI

WiFi.mode(WIFI_STA);

WiFiStart();

// waiting

delay(3000);

//DHT init

dht.begin();

// ADC (Soil) init

pinMode(A0, INPUT);

}

void loop() {

// debug

while (client.available()) {

char c = client.read();

Serial.write(c);

}

// read sensor values

float hum = dht.readHumidity();

float temp = dht.readTemperature();

float soil = analogRead(A0);

//Debug

Serial.println("Humidity:"+String(hum,2)+"\tTemperature:"+String(temp,2)+"\tSoil:"+String(soil,2));

//Send values

httpRequest(hum,temp,soil);

//power of sensors and go to deep sleep

delay(500);

digitalWrite(12, LOW);

ESP.deepSleep(postingInterval, WAKE_NO_RFCAL);

delay(1000);

}

//Transmit data to webserver

void httpRequest(float h, float t, float s) {

client.stop();

delay(100);

//build URL

String url = "/newrecord.php?";

url += "temp=";

url += String(t,2);

url += "&humidity=";

url += String(h,2);

url += "&soil=";

url += String(s,2);

// call URL

if (client.connect(server, port)) {

Serial.println("connecting...");

client.print(String("GET ") + url + " HTTP/1.1\r\n" +

"Host: " + server + "\r\n" +

"Connection: close\r\n\r\n");

Serial.println("data submitted.");

delay(10);

} else {

Serial.println("connection failed");

}

// Establish WIFI connection

void WiFiStart()

{

Serial.print("Connecting to ");

Serial.println(ssid);

WiFi.begin(ssid, password);

while (WiFi.status() != WL_CONNECTED)

{

delay(500);

Serial.print(".");

}

Serial.println("");

Serial.println("WiFi connected");

Serial.println(WiFi.localIP());

}

Tag: XCSOURCE FT232RL

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Irrigation Part 7 – ESP8266 Breakout Board

Irrigation- Part 1: A Prototype

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