WiFi for Arduino

Even though this looks like a long post, I have composed it for a friend and unlike mostly everything else on this blog, this is not just for my own reference, so it should be easy to follow and understand (I hope).

The ESP8266

Arduino does not come with WiFi, there are shields from Arduino that provide WiFi, and those shields are based on ESP8266 which is a very cheap WiFi enabled microcontroller. but there is nothing stopping you from using any ESP8266 board and connecting it to your Arduino, they all should work, and you probably already have them since you are here, models from the 01 (5 boards for $12 ) up to the 12E or 12F (3 for $14). so that is basically around $2.5 to $4.6, not bad for WiFi and a microcontroller !

Communication between Arduino and ESP8266

Arduino can talk to the shield either via UART or via SPI (Given the libraries written for this), SPI is up to three times faster than UART, but most of the time your application, be it sensor data or the like will not be able to flood any of those 2 buses, So i will be going with serial for certain advantages (convenience mainly) provided by serial.

The hardware

1- ESP8266 (Any variant should do)
2- Logic level shifter, since Arduino is 5V and ESPs are 3.3, I have been told that the ESP 12E and 12F are 5 volt logic tolerant, but I would think going with a logic shifter might save me something down the road, hours of debugging, or a new board, or something i fail to foresee
3- An Arduino, I am using a mega, but an UNO should do just fine (I will cover it)
4- Wires to connect all the above, and probably a breadboard (I like to solder things to a board, but not everyone likes to do this)
5- A couple of micro USB cables that i use as a power supply

Let us get to the software you will need to download whether you are looking to have them connected in SPI or serial.

Software on the ESP8266

1:SPI: If you are going with SPI, you will need to flash JiriBilek / WiFiSpiESP onto your ESP8266, fortunately, this comes with an ino file that you can use your Arduino software to flash directly

2:UART-Serial: If you are going with serial (Like i am in this tutorial), you might want to go with jeelabs / esp-link, mind you, Arduino themselves forked this before for their own WiFi shields, but since then, the jeelabs esp-link has added many features, so i would recommend you go with the original jeelabs.

Software on your Arduino

1:SPI: if you have installed the SPI software from above on your ESP8266, the accompanying Arduino software would be JiriBilek / WiFiSpi, The library implements almost the same functions as the Arduino WiFi library.

2:UART-Serial: there is no library to go with this case that is beyond your regular serial bus if you want to exchange serial info, so if this is a 3D printer, software on your PC should be able to translate the data into serial, and it would be transparent, but what if you want to use WiFi from within Arduino, like a client that downloads pages or sends post data to pages,

Choice of UART-Serial

With UART-SERIAL, i can simply update the software on the Arduino over the air on WiFi, I can get serial messages and use WiFi at the same time both as client and server, this may all be possible with SPI, but there are complications and extra work to be done !

So from this point on, I will be focusing on using UART-Serial, and hopefully when i have time i can demonstrate how the SPI software might work in the same way but it should be easy to adapt what you learn here there, the details are available on SPI on the GitHub pages

Connecting the boards together

The ESP8266 has a TX and RX pin that should be connected in reverse to the ones on the Arduino, RX (Receive) should be connected to send, and send to receive, both boards need to share a common ground (reference voltage), and an Arduino mega should be able to provide 3.3 volts with sufficient current for the ESP8266, if you have an ESP8266 with an onboard voltage regulator, you can simply add it to the power supply directly through the VIN pin (rather than the 3.3V pin)

Uploading jeelabs esp-link to the ESP8266

Start by downloading the zip file from GitHub,

Phone charging speed sometimes slow

1- Low quality or damaged wire

The most common reason for this is your cable, a charging cable that has higher resistance (worse thinner or damaged wire) will tell the phone to charge slower, reason for that is that your phone does not want to overwhelm a cable beyond it’s capacity and cause it to burn or even cause fires, but how does the phone know, well, ohm’s law will let it know, a voltage drop at the wire end once a load is attached (the charging is a load) tells it all it needs to know. then the phone can determine a safe current to draw.

2- Phone is already nearing a full charge

Because of how lithium batteries work, a phone can not charge the upper 10% (Or more) at full speed, speed is reduced as the phone gets full to protect the battery from degradation

3- Battery is overheating

Your phone will charge a hot battery slower, so if your phone is sitting in sunlight or is hot in general, it will charge at reduced speeds, this as well is to protect the battery from degradation or even becoming a hazard.

4- Your power brick capabilities

Power bricks are voltage and current regulated power supplies, but they lose capacity over time and degrade, sometimes, their connection with the cable is not clean, or the plating on the pins has worn out, or the spring like mechanism of the pins no longer holds the pin tight against the pins on the USB cable, sometimes it has low capacity to begin with by design

5- Your phone has a Quick Charge capability but your wall adapter does not

Many modern phones, especially on the higher ends have a fast charging feature, where the power brick provides a higher voltage rather than a higher current, your phone will first negotiate this capability with the charger, if your charger does not support this feature, rest assured, it won’t work, and the phone will fall back to 5V charging.

If you have any questions about this matter, feel free to ask me in the comments section


Prolonging the life of your phone or laptop or tablet battery

Is Arduino pro mini 3.3V 5V logic tolerant ?

No and yes, at your own risk.

You can run the whole board on 5V, but that has to be done at the VCC pin (With an external regulated power supply) not the RAW pin, it will still run on an 8Mhz clock (The resonator is 8MHZ, you can’t change that without changing the resonator), and you will lose the voltage regulator (Since it is 3.3v) and use an external one.

Why can’t i, i hear you cry, the answer is simple, the CPU’s reference voltage is 0-3.3V when running on the built in regulator or 3.3V, if you step the voltage up on VCC to 5V regulated, and disconnect RAW altogether, and don’t care about the lower speed, then there you have it, it should work.

If any of my 3.3V Arduino boards gets fried this way, I will let you know, but for now this works for me.

Everything about the Arduino Mega 2560 Pro Embed

In this post, I am simply making a reference of the Arduino mega 2560 Pro Embed so that i can find the info easily when i need it again

The Arduino pro mega embed is basically the same MCU (CPU) as the Arduino Mega, but instead of using it for shields, it is better suited for a printed circuit board.

Where to get it

The board is all over the place, Amazon, Ebay, and other providers, I found one on amazon for $11.71 and people seem to be happy with the seller,
$11.71 – Mega Pro Embed on Amazon
mind you, buying it through this link will earn me 2% of the sale.

Size and installation

The Arduino Mega Pro Embed is a third (1/3) of the size of the MEGA at 38X55mm, the length of the Mega pro embed is the same as the width of the MEGA, and the width of the mega pro is a third of the length of the MEGA

There are 2 mounting holes on the board, making it east to mount with a couple of standoffs if needed, the same standoffs you would use to mount a PC motherboard into a case.

Chips (Logic)

The MCU is the same (ATmega2560) with almost all of it’s pins broken out, it has a TTL USB adapter CH340G (Drivers here).


The board has 86 pins (Regular Mega has 96, the additional ones are either duplicated or not functional), the Mega Pro Embed has the following 86 pins

2 5V
2 3.3V
1 Reset
54 Digital (14 of which are PWM capable)
16 ADC
4 UART bus
6 ICSP Pins are directly connected to digital pins D48 – D53 (Duplicates)


It accepts power in the range of 7-9 (18V peak for a very short time) 7 is recommended, it has two voltage regulators, 5V and 3.3V (800ma each)


The board has 2 resonators, 12Mhz and 16Mhz, the 12 is for the CH340G while the 16 is for the ATmega2560


Microcontroller ATmega2560
USB-TTL converter CH340
Power Out 5V-800mA
Power IN. 5V
Power IN. VIN/DC Jack 5V
Power Consumption 5V 220mA
Logic Level 5V
Clock Frequency 16MHz
Operating Supply Voltage 5V
Digital I/O 54
Analog I/O 16
Memory Size 256kb
Data RAM Type/Size 8Kb
Data ROM Type/Size 4Kb
Interface Type ISP
Operating temperature −40С°/+85С°
Length x Width 38×54mm


The board’s logic is 5V
MOSI – D51 or ICSP-4
MISO – D50 or ICSP-1
SCK (Serial Clock)- D52 or ICSP-3
SS (Slave) D53 – set as output as the library does not support slave.


20 (SDA), 21 (SCL) MEGA 2560 board has pull-up resistors on pins 20 – 21 onboard.

A super simple IOT home electric meter / record keeper

Simple IOT project of the day, a super simple IOT home electric meter / record keeper, without a need to modify anything at home.

  • Before you Start – This is very simple hands on
  • What is it – It’s a home electric meter that counts in both directions
  • What is it for – Keeping track of power consumption
  • How it is done – A clamp meter and a microcontroller board
  • Show me before i begin – A photo gallery
  • Components – What you need
  • Steps – steps to making the device

Before you start, you only need the first few paragraphs to construct this device, the rest of the blog post is simply an explanation of why we did things this way, the whole tutorial should be very simple to follow step by step. Photos of everything you need are also provided 😉 If you know how to solder, you can get through this. if you don’t, find a tutorial on YouTube on how to solder.

What is it

It is a simple always on clamp meter that keeps track of power consumption on a small server (Online, or at home), added in the same cabinet as the utility meter installed by the power company.

What is it for

Since this device allows me to continuously keep track of power consumption, and graph it, I can track down things that are not functioning as they should and drawing much more electricity than they should.

The idea was inspired by the fact that my water cooler was drawing way too much power, and it turned out that it was heating the water it cooled and cooling the water it heated ! so it was basically “on” for far longer periods than it should, the fault turned out to be a loose plastic piece in the cooler’s water tank.

How is it done

A cheap current transformer (Clamp) is attached to a microcontroller that is WIFI enabled, the microcontroller sends the readings to a server in the basement (That server is used for 1001 other things too).

Show me before i dig in

Here is a small gallery of everything you might want to see before you even begin !




NOTE: This tutorial will show you how to do this with an ESP32 board as well as my own setup which is a combination of ESP8266 and Arduino pro mini

The components I chose here are mostly because i already have them lying around, if you are going the ESP32 route, I will cover it too.

  • 2 current transformers to take readings for 2 electric meters, in this example, they are the sct013 100A / 50mA
  • 2 Microcontroller boards, an esp8266 (esp8266MOF-12E) and an Arduino pro mini 3.3V (8MHz) (ESP32 is also covered as a single board)
  • A lousy 5V phone charger that is not capable of providing enough current to charge a modern phone in a timely fashion, but should do for this as long as we have a voltage of above 4.1V.
  • An LD33CV voltage regulator combined with 2 capacitors (10V – 680uF) each.
  • 1 x 10uF capacitor
  • An 23.34ohm resistor (Either series resistors or step down) as a burden resistor if you are using 3.3V board such as ESP8266 or ESP32, or a 35.36 ohm resistor if you are using a 5V board. if the values can’t be made with resistors in series, you need to go DOWN with the value to the next resistance value
  • 2 SCT013 – 100A – 50mA current transformers
  • A pair of equal resistance resistors as a voltage divider, the values are anything between 10 kΩ and 400 kΩ (The smaller is more precise, the larger resistance consumes less battery)
  • A 5CM x 7CM Universal PCB Board

And obviously you need to use a soldering iron unless you wish to use a breadboard.

IMPORTANT: I recommend you use 1 ESP32 board instead of my setup, and use the analogue inputs on that, AND SKIP MUCH OF THIS BUSINESS, one thing to note though is that the ESP32 has one of it’s 2 ADC channels disabled when WiFi is enabled (A channel with X Analogue pins), I will cover this so don’t worry.

So why did i make it with an Arduino pro mini (3.3V) and an ESP8266 connected together in SPI (Against my own recommendation) ? that is because i got those current transformers and went to sleep, by the time i woke up, it was 12:43AM, I woke up and decided on the project, and those are the parts that were at hand that very minute, the Arduino has 8 usable analogue inputs (for sensing the current passing through the current transformer) , The ESP8266 on the other hand has 1 analogue pin and i wish to connect 2 clamp meters to this board

The Arduino pro mini (or any other using the ATmega328 micro controller) only has 6 ADC pins available instead of 8 if you use I2C as 2 are for I2C

Now, let us get to making it, this project takes a few hours to make, and you might want to change some things as i don’t think you need to have 2 microcontrollers connected together in SPI (I don’t remember why i chose that over I2C).

I won’t get too much into why I am using these resistor values, Just use them.
Hint: the reason for the choice is obviously ohm’s law, once for telling the current from the voltage drop using the burden resistor, the other two are a simple voltage divider (use an online voltage divider calculator if you need something different)

Step 1: Cut the endings of the SCT013current transformers to expose the wires, in my case, he SCT013-50mA came with a audio stereo jack, the tip (usually left speaker) was connected to the white wire, the sleeve (usually ground) was connected to the red wire, and the ring (middle usually right speaker) was not connected to anything, the shield on the wire exists but is not connected to any pins on the jack side.

What we need to connect in this case above is the white wire (tip) to the center of the voltage divider, and the red wire to the analogue input pin of the Arduino, the sleeve of the cable which is not connected to anything on any side should be connected directly to the ground pin of the Arduino .

Now, to see the connections, you might want to inspect this photo, I have used Photoshop to make it clearer and to point out where components are connected.

Mounting a disk image in Linux

The new way of mounting a disk image created with dd, dd_rescue, or ddrescue has become much simpler than before, all you need now is to issue the command

losetup --partscan --find --show disk.img

then above will tell you what loop device is being used, let us assume it is /dev/loop0, right after, a quick fdisk -l should show you the partitions, in my case, i have /dev/loop0p1 and /dev/loop0p2

mount /dev/loop0p1 /mnt

now, the first partition is mounted, to reverse this, you will need to first unmount /mnt then, you can delete the loop device with

losetup -d /dev/loop0

And you are done

8 Chan relay module with arduino pro mini 3.3v

To begin with, an Arduino pro mini is capable of driving the 8 port relay with optocouplers, the power required to drive the mechanical relay is provided separately with the most common relay boards on the market, this photo (And video) should demonstrate that

8 channel relay module for arduino

The image above demonstrates the wiring, the power supply is a computer power supply, the relay module uses the 5V power lines from the power supply, while the Arduino uses the 3V3 line, the board’s control lines will work on logic low, hence, it will work when we are below 2V, it works perfectly fine with the 3.3V from the Arduino.

here is the source code (Very simple code, just to pull the digital lines low, then high again, the delay in the engagement is just for fun.)

// constants won't change. Used here to set a pin number:
const int ledPin =  LED_BUILTIN;// the number of the LED pin
const int relay1 = 2;
const int relay2 = 3;
const int relay3 = 4;
const int relay4 = 5;
const int relay5 = 6;
const int relay6 = 7;
const int relay7 = 8;
const int relay8 = 9;

// Variables will change:
int ledState = LOW;             // ledState used to set the LED

// Generally, you should use "unsigned long" for variables that hold time
// The value will quickly become too large for an int to store
unsigned long previousMillis = 0;        // will store last time LED was updated

// constants won't change:
const long interval = 2000;           // interval at which to blink (milliseconds)

void setup() {
  // set the digital pin as output:
  pinMode(ledPin, OUTPUT);
  pinMode(relay1, OUTPUT);
  pinMode(relay2, OUTPUT);
  pinMode(relay3, OUTPUT);
  pinMode(relay4, OUTPUT);
  pinMode(relay5, OUTPUT);
  pinMode(relay6, OUTPUT);
  pinMode(relay7, OUTPUT);
  pinMode(relay8, OUTPUT);

void loop() {
  // here is where you'd put code that needs to be running all the time.

  // check to see if it's time to blink the LED; that is, if the difference
  // between the current time and last time you blinked the LED is bigger than
  // the interval at which you want to blink the LED.
  unsigned long currentMillis = millis();

  if (currentMillis - previousMillis >= interval) {
    // save the last time you blinked the LED
    previousMillis = currentMillis;

    // if the LED is off turn it on and vice-versa:
    if (ledState == LOW) {
      ledState = HIGH;
      digitalWrite(ledPin, ledState);
      digitalWrite(relay1, ledState);
      digitalWrite(relay2, ledState);
      digitalWrite(relay3, ledState);
      digitalWrite(relay4, ledState);
      digitalWrite(relay5, ledState);
      digitalWrite(relay6, ledState);
      digitalWrite(relay7, ledState);
      digitalWrite(relay8, ledState);
      ledState = LOW;
      digitalWrite(ledPin, ledState);
      ledState = HIGH;
      digitalWrite(ledPin, ledState);
      digitalWrite(relay2, ledState);
    } else {
      ledState = LOW;
      digitalWrite(ledPin, ledState);
      digitalWrite(relay1, ledState);
      digitalWrite(relay2, ledState);
      digitalWrite(relay3, ledState);
      digitalWrite(relay4, ledState);
      digitalWrite(relay5, ledState);
      digitalWrite(relay6, ledState);
      digitalWrite(relay7, ledState);
      digitalWrite(relay8, ledState);
      ledState = HIGH;
      digitalWrite(relay8, ledState);
      ledState = LOW;
      digitalWrite(relay8, ledState);
      ledState = HIGH;
      digitalWrite(relay8, ledState);
      ledState = LOW;
      digitalWrite(relay8, ledState);

    // set the LED with the ledState of the variable:
    //digitalWrite(ledPin, ledState);

How to tell if the arduino pro mini is 5V (16mhz) or 3.3V (8MHZ)

if it is not checked on the back side, the simplest and fastest way to do this is to look at the resonator, (Clock) – usually a Crystal oscillator, but I don’t see why it can’t be a ceramic resonator, if it has something with an 8 in it, then it is probably an 8MHZ resonator, otherwise it is probably 16, where 8 comes with the 3.3V and 16 with the 5V (Scroll down to see an example)

Another way is to connect the RAW to, let’s say 12V or even 5V, and measure the voltage at the VCC pin, that would also tell you, but surely, this involves more than just looking at the board, you need to connect wires and a power supply !

mine reads 80 u (something that looks like the letter U) so it is 3v3, here is a photo

Programming the 3.3V arduino pro mini with a CP2102 breakout

The CP2102 breakout board shown in the photo below has a selector between 3.3V and 5V.

In my case, i simply connected it the way you see it here to a USB port with 3.3V, and what do you know, it works, I have a flashing red light on the Arduino, a constant green light, and it looks like it is read to take code, the CP2102 board has a constant red light.

if you want to check that it is actually working fine, simply upload the sketch blink no delay, and then alter it a bit so that it does a double blink then wait 2 seconds, now your code is working, there you have it.

From the device manager, I can see that there is a device that looks like my adapter, namely this one

Silicon Labs CP210x USB to UART Bridge (Com3)

That thing above tells me that it has been designated the communication port number 3, which i will need in the Arduino IDE

So now i have installed and am running the Arduino IDE, selected a 3.3V Arduino board from the list and selected Com3, now i should be ready to upload a sketch, let us make a sketch that double flashes an LED every 2 seconds. here is some code to do that

The cheapest 3.3V power supply using the LD33CV (LD1117V33)

To create a tiny power supply to turn a 5V power source into 3.3V for powering the ESP8266 or ESP32, or maybe an Arduino pro mini (3.3V version), all you need to do is to couple the LD33CV-LD1117V33 with a pair of capacitors, in my case I am using the 25V/100 uf capacitor

All you need to do is the following

connect one capacitor to the pins 1 (Vin) and 3 (GND), and the other to the pins 2(Vout) and 3 (GND), and you are done.

At this stage, the ones between 1 and 3 will receive the input 5V power, While the ones closer to each other (2 and 3) will have the 3v3 output voltage that you can connect directly to your Arduino or ESP micro controller

The LD1117V33 you see above (LD33CV) comes in a TO-220 package, and uses an NPN pass transistor for efficiency to provide up to 800ma of power (Cooling may be needed to achieve maximum)