Author Archives: jechavarria

Free PCB Mega New Year Give Away 2014 – Grab Your Surprise Gift

A brief entry to tell you that Numato people are very happy this year, and from December 2013 and January 2014 they will give a free gift (including worlwide shipping costs) to everyone that shares this message over facebook, twitter or in a blog. Here’s all the info about this mega Give Away. From here, I only can congratulate they for this great initiative.

From Spain, I wish a Merry Christmas for everyone and I hope all of you enjoy this hollidays with your family and friends!!

  • Twitter
  • del.icio.us
  • Digg
  • Facebook
  • Technorati
  • Reddit
  • Yahoo Buzz
  • StumbleUpon

SIM900 Breakout Board

SIM900 Breakout BoardAfter some months out, I come back with my last board, the SIM900 Breakout Board. It’s a board based on the popular SIM900 GSM modem, and I design to work with the DSETA board I develop previously. Also, the board can be used without this board, I try to design it in the way that can be used with any microcontroller. From here, I want thanks to Ioannis Kedros from Embedded Day his support in the design of the battery charger, and to Sonia Muñoz, FAE from EBV, a great professional and a better friend, she always helps me when I need. So, let’s go to see what’s inside the board! Continue reading

  • Twitter
  • del.icio.us
  • Digg
  • Facebook
  • Technorati
  • Reddit
  • Yahoo Buzz
  • StumbleUpon

Components I Usually Use (II): 24LC256 – I2C EEPROM Memory

I resume this brief series of articles with another device I usually use. It’s the popular 24LC256 I2C EEPROM memory, from Microchip. First of all, you can find the datasheet here. This memory has a 32K x 8 bytes of capacity (36768 bytes if you prefer), and can works between 1.7V to 5.5V, with a maximun clock frequency of 1MHz (FC model with Vcc > 2.5V). Of course, it’s compatible with the 100khz and 400khz standard speeds. Here’s a block diagram of this memory:

24LC256 Block Diagram

Continue reading

  • Twitter
  • del.icio.us
  • Digg
  • Facebook
  • Technorati
  • Reddit
  • Yahoo Buzz
  • StumbleUpon

DSETA board, a CPU based on the Atmel AT89C51RE2

DSETA CPU based on AT89C51RE2 ATMEL microcontroller

In my last projects, I always use the same CPU. DSETA board, I say in the posts. Well, here it is, a CPU based on the AT89C51RE2 microcontroller from Atmel. I develop this board for some reasons. The first and main one is because I want to have a small board with a great (an known) 8-bit microcontroller, ready to use and with many of the peripherals I usually use. The other reason is that I want to test the PCB service from Seeedstudio, a PCB manufacturer from Shenzhen, China. Here are the results. Continue reading

  • Twitter
  • del.icio.us
  • Digg
  • Facebook
  • Technorati
  • Reddit
  • Yahoo Buzz
  • StumbleUpon

How to interface 8 LCD displays and 24 leds with only two wires

DSC01259

A couple of weeks ago, I just post a review of my MCP23017 breakout board. As the board configuration allows to connect up to 8 of these boards, I decided to do it and see that it really works. My goal is interface 8 LCD displays with two wires: SDA and SCL from an I2C bus. With direct IO`s of a microcontroller, you need at least 48 lines to control all the displays. With this option (and a little of software, of course), you can do this with only two lines.

Continue reading

  • Twitter
  • del.icio.us
  • Digg
  • Facebook
  • Technorati
  • Reddit
  • Yahoo Buzz
  • StumbleUpon
MCP23017 Breakout Board

MCP23017 Breakout Board

I develop this MCP23017 Breakout Board to interface a 2×16 LCD display with any microcontroller using a standard I2C bus. Typical 2×16 displays needs at least 6 lines to work (when working in 4-byte mode); in some cases, this will be prohibited for some microcontrollers. With this board, you can control it with only two lines (I2C bus) and, by the same price, obtain a few more IO’s. I use the MCP23017 I2C expander as a bridge. This integrated circuit provides 16 IO’s over a standard I2C bus. All the pins can configure as inputs or outputs independently, and supports high speed I2C (up to 1,7MHz). Also, this device has three hardware address pins that allow connecting up to 8 devices in the same bus. The rest of the features can be seen in the datasheet.

UPDATE: Dominic Amann shared this board on OSH Park, you can order here: https://oshpark.com/shared_projects/KNHdhwLN Continue reading

  • Twitter
  • del.icio.us
  • Digg
  • Facebook
  • Technorati
  • Reddit
  • Yahoo Buzz
  • StumbleUpon

7-Segment Counter for Kids

7 Segment Counter

Here it is. This project starts four weeks ago, when my daughter shows running the Digital Paddle Clock that I receive from Dangerous Prototypes. She has four years old and she loves count. She can count up to 30 (more or less), but she doesn’t recognize high numbers when she sees written. So, I decide to make a counter with two 7-segment displays and increment a decrement pushbuttons, so she can count pressing buttons and see the numbers in the displays. Continue reading

  • Twitter
  • del.icio.us
  • Digg
  • Facebook
  • Technorati
  • Reddit
  • Yahoo Buzz
  • StumbleUpon

Components I Usually Use (I): DS28CM00 – I2C Serial Number

I want to start a serie of brief articles describing the components that I usually used in my electronic designs.The first one is the DS28CM00 I2C serial number. This device is an electronic registration number that gives you an unique 64-bit serial number over I2C or SMBUS interface. This 64-bit serial number is  factory lasered, so there aren’t  two devices with the same number.

I use this component in a railway application, to identify the PCB’s mounted in the system. The pinout and the typical connection of this device is shown here:

DS28CM00 I2C Serial Number

Continue reading

  • Twitter
  • del.icio.us
  • Digg
  • Facebook
  • Technorati
  • Reddit
  • Yahoo Buzz
  • StumbleUpon