November 20, 2014

Open source - explained in LEGO!

   Browsing the internet (as I do every single day of my life) sometimes exposes me to some very interesting stuff; as for example this video (below), explaining with LEGO (in stop motion) how does the Open source movement works. That's some worth-watching-content, for sure!.

October 21, 2014

A substitute for the DELAY function - Arduino

Hello guys, how are you doing today? 

   Ever since I came across the Arduino platform, I felt really pissed off with (the existence) of the delay() function, because it was created with the (evil) solo purpose of wasting time between executions of the loop() function. 
   I have rapidly created a counter to substitute this function in every sketch of my own, with the downside of having to adjust the counted number for every single program (because different program sizes take different times to be executed). This scenario have just changed, because I am presenting you my very own professional way to not waste precious time of your Arduino. It is a sketch that allows you to run a piece of code every 'x' microseconds while leaving the rest of the time free for execution of more code!. 
   The code takes advantage of the micros() function, present in the stock Arduino language and IDE, which returns the time (in microseconds) that Arduino has been running since the last reset. Essentially what I do is to execute my main function (which I can freely choose) only every given time; this "given" time can be adjusted by updating its value (in microseconds) in an IF loop.

   The sketch is available on my GitHub and doesn't require any special library or installation, only the stock micros() function. Essentially your custom code, such as blinking leds, goes in between the quotes I have wrote (as seen below): 

   The main advantage in this code is that you can execute a code every 'x' microseconds (utilizing the sketch exactly as it is) or multiple codes every 'y' microseconds (by adding new IF conditions based on the same couter). You can not forget to fill your setup() function as needed; your timing will always be respected, since you don't write a code big enough (that takes more time than your delay) to be executed. 
   I would greatly appreciate to hear from you guys, any suggestion, criticism, upsides, downsizes, anything that can make the code work better. You can reach me on twitter @embedded_clovis or email: clovisf AT gmail DOT com .  

September 19, 2014

Those are my thoughts about solar roads

So I am bringing something different for you guys today! It is a video that really reflects my thoughts on the recently-IndieGoGo-funded Solar roadways:

And they have raised over $2M dollars :) . 

September 05, 2014

Beta-testing Arduino-ZERO

Hi guys, this is just an update post to tell you two things: 

1- I will be back to this blog once I go forward on my "chip tag for running clubs" project and once the things stabilize in the college (beginning of a new term is always crazy!).

2- I was selected as one of the Arduino-ZERO (link here) beta-testers! It has been so nice and so crazy test everything on that board, you have no idea. I have signed a waiver saying that I cannot share any information related to the platform, so I will only be telling you things related to this project when the beta-testing is over (and the product releases).

Stay tuned for news, and happy coding and hacking!! :-)

July 23, 2014

RFID tag reader with ARM microcontroller

   Good afternoon makers, and welcome back to Embedded-Clovis blog. Today I will show you one of the first steps in the make of my Chip Tag for every running club (click here) project: the RFID tag reader. It is a part of a Hackaday prize project I am in, so I think it is important to share it with you.
   RFID stands for Radio-Frequency identification and is a technology that reads/writes tag's (cards, keychains, tokens) contactless (by air); it may or may not feature a power supply in the target device, and when it doesn't have a power supply the energy for the target comes from the air as well (from the host device).
   I bought the module RFID-RC522 breakout board from a random seller on eBay, that features a MFRC522 RFID chip from NXP working on 13.56MHz; I also bought some programmable RFID cards/keychains for testing: the MIFARE 1K . I haven't tested recording data on it but this is surely the next step in my journey (since I will need that on my "Chip tag for runner's" project. 
   The schematic of my project can be seen below, featuring a Freescale FRDM-K64F development board, a RFID-RC522 module and an USB cable connected to my PC. Every time a card is ready (in a 2-3 centimeters range) its data is sent to a serial console on PC: I am using the Arduino IDE console on this project. 

click in the image to Enlarge

The wiring is done as follow: 

MFRC522 SPI_MOSI => PTD2 port of my board
MFRC522 SPI_MISO => PTD3 port of my board
MFRC522 SPI_SCK => PTD1 port of my board
MFRC522 SPI_CS => PTE25 port of my board
MFRC522 MF_RESET => PTD0 port of my board
MFRC522 3.3V => 3.3V of my board
MFRC522 GND => GND of my board

   There is a test code on GitHub here,  for reading tags and sending its information to the serial console of a PC. It is important to mention here that most of the code was taken from libraries and examples created by other users on the mBed platform (please refer to the GitHub link above for credit information).
   This was only the first step on the development of my summer project (Chip tag for running clubs), but I am sure it will help people get started with RFID technology. Having any question or concern, please contact me via Twitter: @ClovisDuino  or e-mail: clovisduino AT gmail .com . See you guys next time; have fun hacking and making!. 

July 04, 2014

Weather datalogger with ARM cortex-M4 - part1

   So, after blinking LED's and reading buttons I want to go further and deeper inside my ARM Cortex-M4 board: I am developing a data-logger for Temperature, Humidity and light level; It will store its data inside a micro-SD card, available on-board the FRDM-K64F I have.
   The sensors I have in my hands right now are the linear LM35 temperature sensor, the DHT11 digital temperature/humidity sensor and a LDR(light dependent resistor) for visible light level measurement. In the picture below you can see the setup of my experiment; it is  possible to see the big light-blue component (DHT11) aside with LM35 (the TO-92 case) and my Freescale development board with a microSD card connected to it. The LDR is missing in the picture, but is present in the actual prototype.

   Besides the sensors and microSD my board also features a Timekeeping chip, a Maxim DS1302 in a breakout board with a battery mounted on it; That chip makes my data-logging look more "professional" by keeping track of the time of every reading (or event). My code can be download from here and the schematic diagram is seeing below. 

Schematics- click the image to enlarge

   One reading is made every 10 seconds and the data is stored in the microSD card. I have tested the setup for several days, for as long as 21 hours every time. Turns out the system is very reliable: it can be seen below in the temperature plot that both sensors feature a similar behavior, validating the reading of both (analog for the LM35 and digital-serial for the DHT11).

Click in the images to enlarge

   I selected that specific period of time (5AM- 5PM) because it is the most interesting in terms of temperature and light level; There are some considerations to be done in here:

1) The temperature and the light level increase when 5PM gets closer, and that is because my room is facing northwest, so it starts getting a huge amount of sunlight around that time.
2) My light sensor (LDR) is not calibrated and I also don't know its characteristics, so I simply put a series resistor (1Kohm) with it; As a post processing I scale it to fit into a 0-5 arbitrary scale. Around 7:30PM (not on the pictures above) it reaches almost 4.5 with direct sunlight over it.
3) Some noise is expected to appear in the pictures above (as is possible to observe), as the system takes one measurement every 10 seconds. These pictures feature around 12 hours of data!.

   That was the part 1 of a series of improvements I am planning to make on that project; My next step will be using the network hardware available on-board (Ethernet) to send all that data in real-time for a web page I will create. Another piece of future work will also be powering the module with a solar panel (which I have bought already). And finally adding a rain sensor to it, so I can have a complete meteorological station in my house!. All of that was powered by this amazing Freescale development board (FRDM-K64F). 

Thank you guys and see you soon,

July 03, 2014

A cheap Chip Tag for every Running club

Hello folks, 

   Today's post is about my entry to the Hackaday Prize, a competition that will take its winner to space :) . The objective of the competition is to make (and show the world how you did) projects that are in some way "connected": any kind of communication is valid. There is already a plenty of projects being showed there, and I think mine is a bit special: it is related to something that I love doing and will help me doing it better.
   I am talking about road Running; I have been running for three years now and I always feel frustrated when there is no chip-timing in the small races I participate, or even in trail or stairs races. Of course everyone can have a GPS-enable Cellphone or wrist-watch, but the first ones are not always comfortable to carry and the last one in not cheap enough for everyone to have it.
   So I came up with a hack solution (link here) that may revolutionize small running communities and clubs: An Arduino-sized device that reads RFID tags and communicates to any Android cellphone via Bluetooth. So every runner will only carry a small key-chain sized RFID tag and all the processing is done into the reader, that will finally send runner's time and name to an App to be developed on Android.

   The actual schematic for the project is seen above; I haven't started putting the hardware together yet because the parts are still being shipped to me, but have started the programming, that will probably be done into a Freescale FRDM-K64F board (features an ARM Cortex-M4 inside). 
   More details to come as I advance into the project. Get updated on my Google Plus: +Clovis Fritzen and my Twitter: @ClovisDuino. See you guys later, 

June 27, 2014

Leds and Buttons - Freescale FRDM-K64F

Hi makers, programmers and curious :)

   This post will be about my first contact with the ARM technology, by means of my newly arrived Freescale FRDM-K64F development board. As a good Arduino user the first thing I wanted to do with my board was to blink the RGB led it features onboard, so I did it!. The code I developed can be found here . I got a lot of help and examples from the mBed online compiler.

my first ARM-based project

   The blinking LED example from mBed website uses a "wait()" function which I don't like (because wastes processing time), so I developed my own code based on a counter that controls the "entering or not" in the blinking function. It is possible to notice in the gif image above that all the led colors are being lit, one after another; I was satisfied with the results, so I moved to the next step: adding buttons to it!. 

   Again my code is very simple (and can be found here): when no buttons are pressed the blue LED is on; when the left button is pressed the LED turns green and for the right button the LED turns red. It took me only a few minutes to write, compile and test both circuits!.

buttons and LED's on my ARM board

I hope you guys are enjoying my blog, and I surely want to here from you. See you all soon.

My Brand-new Freescale Freedom board!

Hello everyone,

  Some weeks ago I entered a contest from Freescale Semiconductor, the Montain Mondays: the contest would give away 20 development boards for the ARM Cortex-M4 technology, every monday for five weeks (a total of 100 boards). The board were the FRDM-K64F , Ethernet enabled, onboard SD Card reader and Arduino form-factor. All I had to do is to suggest a possible application for the board. 
   The the board come to me by mail and I started to look around the internet for information about it: surprisingly there are tons of documentation and libraries, including some for most of the Arduino-compatible sensors and actuators. There is even  an online IDE/compiler for the ARM boards: mBed (which is fully compatible with my specific model of board). 

the tiny nice FRDM-K64F from Freescale

   The IDE has a nice design, is light and includes libraries that can be imported into your project almost automatically: if you compile your design without some specific (and necessary) library, the IDE will give you a warning, then you are driven to a search too where there is going to be a list of all "alike" libraries; just click on "import" and you are good to go!. 
   This board can be programmer through a system called "Open SDA", which allows you to simply drag your compiled program into a "disk", which is really the interface of the ARM microcontroller with your computer. It simplifies the process of flashing your device and makes it look nice and fast.
   I would like to thank +Freescale for sending me this board; And also would like to tell you guys that I have been working on a temperature and humidity Data-logger inside this board, which will also be Ethernet capable: and hopefully will become a fully functional meteorological station; More news and updates to come in the next few days. 

My project featured on SeeedStudio

Hello Makers,

   Last Tuesday, June 24th I had a project featured in a contest of Seeed Studio website: my 6-bit Arduino thermometer, that can be seen here. The contest consists of sharing your first maker project, and you can get $5 in credits to use in SeeeD Studio website. I found their initiative very nice, because it encourages other to become makers just like me, and turn the world into a better place.

   The project inside my blog: here
   The project on Seeed Studio: here

June 24, 2014

Second project - Temperature + humidity + LCD!

Hello coders, hackers, makers and curious visitors!

   The second project I worked on is a "temperature and humidity sensor with a LCD display" based on Arduino, the DHT11 serial temperature/humidity sensor, the LM35 linear temperature sensor and a 16x2 LCD screen. The project is similar to this one and features readings of temperature and humidity that are shown in a LCD display and sent via Arduino (USB- serial) to any PC terminal. Below I show a picture of the project working:

The prototype, when compared to Google Weather (upper right corner)

   The serial console (on arduino IDE) can be seen below, capturing successive readings from Arduino serial:

Screenshot of data captured through serial

   The complete schematic of this prototype is in the picture below; it was developed using Fritzing; You can download the schematic here

   The project was coded inside the Arduino IDE using some third-part codes, which I put together and made it work. The original codes are: DHT11 Library and LiquidCrystal . My code is available in the box below, as well as in this Github link.

Modified by Clovis Fritzen in June 11th, 2014:
- The original program read the serial temperature/humidity sensor DHT11 (which is still part of this program);
- "Delay" function substituted by a counter (when the counter overflows the program enters the serial routine)
- Added the LM35 (10mV/C temperature sensor) reading via serial, to compare both sensors
Board int.0 int.1 int.2 int.3 int.4 int.5
Uno, Ethernet 2 3
Mega2560 2 3 21 20 19 18
Leonardo 3 2 0 1
Due (any pin, more info

This example, as difference to the other, make use of the new method acquireAndWait()


int idDHT11pin = 2; //Digital pin for comunications
int idDHT11intNumber = 0; //interrupt number (must be the one that use the previus defined pin (see table above)
long count= 0; // counter for spacing the serial writings
long AcqPeriod= 0;
int sensorPin = A5; // input pin for LM35 (10mV/C)
int sensorValue = 0; // variable to store the LM35 temperature
int led= 13;

void dht11_wrapper(); // must be declared before the lib initialization

// initialize the library with the numbers of the interface pins
LiquidCrystal lcd(9, 8, 5, 4, 3, 6);

// Lib instantiate
idDHT11 DHT11(idDHT11pin,idDHT11intNumber,dht11_wrapper);

void setup()
pinMode(led, OUTPUT);
Serial.println("DHT11 temp/humidity sensor - Example program");
Serial.print("Lib version: ");
Serial.println("modified by Clovis Fritzen");

// set up the LCD's number of columns and rows:
lcd.begin(16, 2);
// Print a message to the LCD.
lcd.print(" DHT:|LM35:|HUM:");
// This wrapper is in charge of calling
// mus be defined like this for the lib work
void dht11_wrapper() {
void loop()

AcqPeriod= 400000; // set here the interval in which data is sent into serial

if (count < AcqPeriod) // Still need to make sure what this number represents in terms of
// seconds or cycles of clock
count= count++;

if (count < (AcqPeriod/2)) // just a routine to blink a led :)
digitalWrite(led, HIGH);
} else{
digitalWrite(led, LOW);

//Serial.print("\nRetrieving information from sensor: ");
Serial.print("\nRead sensor: ");
count= '0';

sensorValue = analogRead(sensorPin);
sensorValue= sensorValue/2;

int result = DHT11.acquireAndWait();
switch (result)
Serial.println("Error\n\r\tChecksum error");
Serial.println("Error\n\r\tISR time out error");
Serial.println("Error\n\r\tResponse time out error");
Serial.println("Error\n\r\tData time out error");
Serial.println("Error\n\r\tDelta time to small");
Serial.println("Error\n\r\tNot started");
Serial.println("Unknown error");

lcd.setCursor(7, 1);
// print the number of seconds since reset:

Serial.print("Humidity (%): ");
Serial.println(DHT11.getHumidity(), 0); // ", 0" represents the number of decimal positions after the comma

Serial.print("DHT11 Temp (oC): ");
Serial.println(DHT11.getCelsius(), 0); // ", 0" represents the number of decimal positions after the comma

lcd.setCursor(13, 1);
// print the number of seconds since reset:
lcd.print(DHT11.getHumidity(), 0);

Serial.print("LM35 Temp (oC): ");

//Serial.print("Temperature (oF): ");
//Serial.println(DHT11.getFahrenheit(), 2);

//Serial.print("Temperature (K): ");
//Serial.println(DHT11.getKelvin(), 2);

//Serial.print("Dew Point (oC): ");

//Serial.print("Dew Point Slow (oC): ");

// set the cursor to column 0, line 1
// (note: line 1 is the second row, since counting begins with 0):
lcd.setCursor(1, 1);
// print the number of seconds since reset:



   I just want to share some notes with you:
- Both the DHT11 and LM35 have a "step" (or resolution) of one degree Celsius, meaning they cannot read something like "26.3"; They a only capable of reading numbers with no decimal (e.g: "26").
- The contrast of the LCD screen can be adjusted by means of the potentiometer; Its backlight is always on (last two pins of the LCD on the schematic above).
- The circuit works independently on the presence of the USB cable on Arduino; it means that it will work on batteries for example!. in this case only the serial readings will be missing.
- The is a blinking led on pin 13 of Arduino (which is assemble on the board); That one is there just for fun.

   I hope you guys are enjoying my posts so far, and trying to validate my projects by doing it yourselves. If you have any suggestions/ recommendations or critics, please feel free to talk to me on Twitter, Google Plus and Facebook, as well as in the comments below. See you all next time!.

June 18, 2014

First project - Arduino Binary Thermometer with LM35

Hello folks! 

   As a first project post I will show you the steps I take to develop a binary thermometer with a LM35 temperature sensor. It is a bit similar to this one from instructables, but mine is arduino-powered. My intention on this project was simply to test the power of arduino (UNO R3) on handling one of its ports (6 bits) at a time, and also the efficacy of the LM35 digital temperature sensor.

The prototype schematic

   The schematic I created was drawn in Fritzing. My code (also available below) can be found in GitHub ( here). It is important to notice that the limits of temperatures that can be read are NOT the ones of the LM35, instead they are limited by the Arduino power supply voltage (0 +5V): so you are able to read  temperatures between +2 and +150 degrees Celsius.

// Arduino timer CTC interrupt example (timer), from
// This example is a binary meter - shows a analog value in a binary (6-bit) output
// Modified by Clovis Fritzen, to fit as a binary thermomter (in may/2014)

// avr-libc library includes
#include < avr/io.h >
#include < avr/interrupt.h >

int sensorPin = A0; // select the input pin for the potentiometer
int sensorValue = 0; // variable to store the value coming from the sensor (LM35)
byte binaryValue= B00000000; // initialize port value as zeros

void setup()
DDRB = DDRB | B00111111; // set 6 pins in port B as outputs

// initialize Timer1
cli(); // disable global interrupts
TCCR1A = 0; // set entire TCCR1A register to 0
TCCR1B = 0; // same for TCCR1B

// set compare match register to desired timer count:
OCR1A = 15624; // for temperature
// turn on CTC mode:
TCCR1B |= (1 << WGM12);
// Set CS10 and CS12 bits for 1024 prescaler:
TCCR1B |= (1 << CS10);
TCCR1B |= (1 << CS12);
// enable timer compare interrupt:
TIMSK1 |= (1 << OCIE1A);
// enable global interrupts:

void loop()
// You would put another stuff program here

// read the value from the sensor :
sensorValue = analogRead(sensorPin);
//digitalValue= sensorValue;
binaryValue= byte(sensorValue/2);
PORTB = binaryValue;

   Some notes:
- The LM35 sensor is connected to the analog input A0;
- I put three colors of leds only to give an impression of "the warmer the color, the warmer the ambient (since the MSB is a red led, connected to pin 13 of arduino);
- I have only tested it indoors so far, and it showed to be accurate enough for a sensor like that, when compared to a DTH11 temperature sensor. 

I hope you have liked it, and I promised I will try to put some videos of the actual circuits working, for the next experiments. 

February 28, 2014

A dream-embedded programmer

Hi Guys, this is Clovis !

   I am a Electrical Engineering student (3rd year) willing to learn embedded programming of microcontrollers and systems. I`m from Brazil but at this moment I`m living in Vancouver (Canada) as an undergraduate exchange student @ UBC. Besides embedded programming I also love to write down everything that I believe to be worth sharing, and that`s why I just started this Blog!!.
   My plan is to learn embedded systems programming and share every step of this journey with you all, so that we can learn and evolve together. Of course this is only the first post (on a warm friday morning during the north-American winter), but I hope I can share more and more details about my student and professional life with you (in posts to come).
   You must be asking yourself which technology I am going to use in order to learn embedded programming, right?. Well, I decided to start with a Freescale ARM cortex M0+, the Freedom Kinetis E-series platform, just because I had a course in my undergrad studies (Microcontrollers) and I learned hot to program on Freescale environment. Another technology I will be using as well is the FPGA, based on a ALTERA DE2 Educational board; I decided to use it because (again) I am taking a course at UBC (digital systems design EECE353) which teaches us how to synthesize logic circuits in VHDL.
   By the next few days you will start to see some very basic posts regarding my first steps into this huge embedded-programming world. See you guys,