Articles, tutorials & how-tos on electronics, Arduino, 3d printing, and more. Here’s the latest articles. Enjoy!

DTMF Decoder IC

If you are looking for a dtmf decoder, your best option is to use a dtmf decoder ic instead of trying to write up software.

Using software in your microcontrdtmf decoder icoller-based project (Arduino or other) to decode dtmf signals to me is like reinventing the wheel.  For sure the software approach is a “free”solution, since you’re not paying for a chip, but you’ll pay the price in development time and possibly performance. Robust dtmf decoding in software is not impossible but is for sure challenging and time consuming.

the easy way: dtmf decoder ic

When it comes to selecting a dtmf decoder ic to do the job, there are two that I recommend. I have been using both for some time now, in my MICO and DTMF boards, and they work great. Here they are:

  • Holtek 9170D link : this ic operates in 2.8 to 5v; and is easy to find for sale
  • Zarlink MT8840DE: this only operates at 5v and is a bit harder to find for sale from authorized distributors. mt8870 datasheet coming soon

Other than the operating voltage I conclude that both IC are functionally identical.

Side note: One interesting fact about these dtmf decoder chips. There seem to be several companies that make the exact same chip: Holtek, Mittel, Zarlink, to name a few. I’m not sure what’s the deal on why so many companies make the exact same die. It may have to do with company acquisitions over time… if I ever find out I’ll update this post.

Save time with dtmf decoder board

dtmf shield for arduinoIf your application require a dtmf decoder ic and you want to save time, feel free to grab the DTMF Shield for Arduino from This development board will help you to cut some days off your project development.

The dtmf shield is very easy to use. You just plug it into your Arduino, load the sample sketch and off you go.

did I mention this shield can also encode dtmf? that’s right, this shield is also a dtmf generator!




Phone Charger Current Comparison

I bought a spare phone charger on eBay several months ago, and I always wondered if that charger was a genuine product or a counterfeit. Looking at it there’s no way of telling. The eBay purchased charger has all the labels just like the original.

I then figured that a way to confirm the charger is genuine is to verify it can charge at the same current level as the charger that came in the box with the phone. And that’s what I set out to do in this experiment!

I’ll do a side-by-side comparison of the charging current of each charger, and I’ll plot the results for easy comparison. In order to do that I’ll use an Arduino Uno board to collect the current and will plot the acquired data in an Excel spreadsheet so that it is very easy to see how each charger compare against the other!


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Setup Cron Job for osTicket in Bluehost cPanel

An important aspect of selling gadgets is what comes next: customer support.

As I’m shipping out RECAP to my Kickstarter supporters, and am launching the RECAP store where anyone can buy this device that let you record cell phone calls into a Computer, it’s now time to give my customers (and me) a convenient way to handle technical issues.

A way to enter and track issues. osTicket is a great platform to provide that customer support. Especially because it comes free with Bluehost, which is the webhost I use.

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