Microcontrollers

2348 Articles

Barebones PIC RFID Tag

September 26, 2011 by 34 Comments

An inductor and 8-pin microcontroller are all that make up this barebones RFID tag. You might have done a double-take when first seeing the image above. After all, there’s nothing hooked up to the power and ground pins on the chip. As [Ramiro Pareja] explains in his post, the power is actually supplied via the I/O pins to which the inductor is soldered. It seems that each I/O pin has a parasite capacitor and a pair of clamping diodes inside the chip. When the AC current that is induced by the magnetic field of the RFID reader hits those pins, the capacitors charge and the clamping diodes form a bridge rectifier. This results in power being injected into the chip, which turns around and sends the RFID code back through the inductor.

This isn’t the first time that we’ve seen this concept. We featured a hack that is exactly the same except it used an AVR chip. This one uses a PIC 12F683 but should work with just about any 12F or 16F model. The code is written in Assembly and shouldn’t need any changes for different hardware. [Ramiro] does talk a bit about adding a decoupling capacitor to Vss and Vdd, as well as a tuning capacitor to the two I/O pins used above to help make the device a little more robust. But, as you can see in the video after the break, it works just fine without them.

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ATtiny Hacks: ATtiny45/85 Servo Library

September 25, 2011 by 6 Comments

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Servo8bit is a library for AVR microcontrollers that allows you to drive servo motors without the need for a 16-bit timer. Obviously, this is quite useful for smaller chips that only have 8-bit timers and it is specifically targeted at the ATtiny45 and ATtiny85 microcontrollers. The library offers 256 steps of resolution, and can drive up to five servos at one time. Servo control pulses can be generated between 512 and 2560 microseconds and if you don’t mind increasing the time between these pulses [Liya] says it would be possible to increase the 5-servo limit.

The library is quite easy to use, but in its current state it would take just a bit of work to port to another device. It’s been written for an 8 Mhz clock signal with PortB used to drive the motors. Using find-and-replace to change the PORTB keywords to use a DEFINE variable should be easy enough, but we don’t know how hard it would be to change the clock frequency.

We wonder if it’s possible to make this a slave device, perhaps implementing a 1-wire protocol?

ATtiny Hacks: ATtiny10 Game – Doing More With Less

September 24, 2011 by 12 Comments

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Okay, you’ve got a six-pin microcontroller with 1k of program memory, 32 bytes of SRAM, and it can’t be programmed using an In-System-Programmer. Do you think you can use it to develop a game? [Wrtlprnft] managed to build a Simon Says game based on the diminutive device that has four buttons and four LEDs. Judging from the video after the break, we’d say he nailed it!

There are so many design challenges here. First off, with only six pins total getting eight devices connected and working means doubling up on each I/O pin and using the reset pin as a doubled-up I/O. We’ve seen momentary push buttons on the same pins as LEDs before, so that’s not too hard to get working.

But if you’re using the reset pin how do you flash the thing? It doesn’t use the same ISP programming protocol that it’s bigger cousins do, so [Wrtlprnft] used an ATmega1284P to program it, hooking up to the three I/O pins and using a transistor to push 12V on the reset pin. But there’s still the matter of writing the code. It has half of the 32 registers you’d expect to find. He ended up ditching C and went straight to writing Assembly because of the diminished instruction set. It’s the first thing he’s written in Assembly, and a great way to learn the ropes.

It may not be as polished, but we do like it just as much as the Karate Chop Simon Says game which has a lot of other bells and whistles.

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USB Stick Propeller Development Board

September 23, 2011 by 11 Comments

[Parker Dillmann] is nearing the end of the prototyping process for his Propeller development board. He wanted a tool that let him work on projects without the need for a bunch of equipment, while still maintaining the ability to extend the hardware when necessary. His last dev board used a large piece of protoboard to host through hole components including the Propeller chip, 3.3V and 5V regultors, an SD card reader, and female pin headers. This version migrates to a PCB from a fab house and mostly surface mount components.

He decided to use a USB-stick design having been happy with some of TI’s prototyping tools. The Parallax branded development boards use an FTDI 232RL chip for easy programming and that’s what he’s gone with as well. A P8X32A chip in the QFP package was chosen for easier soldering than the smaller QFN option. There’s also a 64kb EEPROM on board to give you plenty of room for your SPIN programs. All the pins are broken out to DIL female headers and there’s a power header on the end opposite the USB plug. [Parker] plans to do a bit of testing to make sure there’s no problems with signal routing below the 5Mhz crystal footprint. This run of prototypes came from the Seeed Studios Fusion PCB servcie–he got more than 10 boards for a total of $13… that’s almost unbelievable.

ATtiny Hacks: Reading From A Motorcycle’s J1850 Data Bus

September 19, 2011 by 8 Comments

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[TZ] has been using ATtiny microcontrollers to read and pass along data from his Harley Davidson motorcycle. The image you see above is using an ATtiny 4313 to read data from the J1850 bus.

The J1850 protocol is an older standard which may not be available in newer vehicles. But if your vehicle has it, you may be able to tap into the bus through an ODB-II connector. [TZ] is decoding the data with the 4313, then using an inexpensive Bluetooth module to send the information to an Android tablet. Fortunately, someone has already written a nice GUI to display the speed and tachometer.

This isn’t the only approach to data harvesting with an ATtiny chip that he’s explored. There’s a second video after the break that shows a much more complicated setup. It still harvests the J1850 data in the same way, but also uses additional I2C sensors and an embedded ARM board to gather GPS data. Everything is pushed to his smart phone, which displays current gear, RPM, speed, engine temperature, fuel level, and GPS information via a WiFi connection.

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Karate Chop Is Simon Without All The Touching

September 15, 2011 by 9 Comments

[Alan Parekh] and his daughter [Alexis] just premiered their entry in the Avnet Dog Days of Summer contest. It’s a game called Karate Chop that is basically an electronic Simon Says. The video after the break shows a demonstration of the device. When switched on it’ll play a little tune and start cycling the LEDs on the front of the case. Players interact by breaking the infrared beams in the two cutouts on either side of the case. You need to keep your hand flat to do this, which is where the name comes from. There are four different game modes which are selected at the start of the game. There are two difficulty levels of a Simon Says game which shows the player a pattern in light and sound, then watches for the user to repeat that pattern back. The other mode that [Alexis] demonstrates is a reflex game which requires the player to quickly react to randomly illuminated LEDs.

The circuit is built on a breadboard hiding behind the front bezel and uses a PIC 16F1827 microcontroller to drive the game. The case itself is made from laser cut MDF and plywood. We’re not sure how much time [Alan] spent on the case, but we think it looks wonderful. If you’re planning to participate in the contest you better get rolling, the entry deadline is tomorrow.

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Microchip Puts Up Two $1000 Prizes For USB And TCP/IP Stacks!

September 15, 2011 by 37 Comments

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A couple of weeks ago we put up a post titled Addressing Microchip’s open source problem where we talked about some of their shortcomings as far as open source code goes, specifically the TCP/IP stack and the USB stack. The comments were predictably fairly negative. The interesting part here is that Microchip actually listened. If you read through all of the comments, you will get a bit of an inside look at what is going on internally at Microchip. At the very end, [Marc] from Microchip left a couple of comments outlining a pair of prizes for independently ported stacks for TCP/IP and USB. Microchip can’t fully open the ones that they have because of legal reasons so they need the help of the development community and they are putting up $1000 for each one to prove that they are serious. If you follow this link you will arrive at a page outlining the rules for the contest.

The gauntlet has been dropped! Do you have chops to pull this off and earn yourself a cool $1000?