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Hi Jeremy

I'm not an Electronic Engineer so struggling here. I would like to use my Arduino to generate some Wiegand compliant logic signals as an output. So not sure if I should use Digital IO's or Analogue or otherwise (I2C SPI?) and whether I need one or two IO ports to do it. Assuming you're not acquainted with Wiegand, here is my take.

You require two data wires (Data 0 and Data 1). Both are default high at 5V (max 1mA). Having seen your tutorial on I2C (very good by the way) I'm assuming I need somewhere some pull-up resistors (or do I). The Wiegand operates using 26 bit code to transmit the data. This code is generated using the two wires (without a timer clock). Thus if you want to generate a data bit "1" you open the Data 1 line to generate a 0V pulse and similarly for your data bits with zero binary value you use the Data 0 line. The standard is particular about the timings of these (square wavish) pulses. The data pulses for the Data One and Data Zero shall not overlap or occur simultaneously. Pulse Width Time should range from 20microseconds to 100

microseconds and the Pulse Interval Time should be anywhere from 200microseconds to 20milliseconds.

Is this readily done. I'm assuming that one will always need a microcontroller to convert any input - say a mobile phone number or a keypad pin code or any unique identifier and convert this into 26bit format and then send this to my Wiegand signal generator to send the code.

Any help gladly appreciated.

Yes you should be able to write a library for the arduino to accomplish this - It should probably be done in actual C code for efficiency.  I'd start by taking at a look at the I2C library source files for hints.

Yes you should be able to write a library for the arduino to accomplish this - It should probably be done in actual C code for efficiency.  I'd start by taking at a look at the I2C library source files for hints.

Regarding the creation of a Wiegand output, I stumbled across this tutorial: http://arduino.cc/en/Tutorial/SecretsOfArduinoPWM and within this tutorial an additional example and manual creation of PWM: http://www.arduino.cc/playground/Main/PWMallPins

The tutorial describes different methods of manipulating the PWM duty cycle which to me, sounds as if you could use two output pins to create a Wiegand output directly with Arduino rather than a C library. The question is which method would be best, namely:

You can't say which is "best" without an application in mind.  Each will have their merits, but I'm sure only one is the ideal solution in a particular scenario.

Hi BigG,

Since you appear to be knowledgable about both forms of wave generation, why don't you do some experiments and share the data?  Maybe we can assess the merits of both on some test applications and give the whole group some useful data.

Just a thought,

DAB

Hi, I change in my arduino chip, befor use atmega 328, now I put in socket atmega8 16PU, and dont work he, what is problem.

Thanks in advance

You need a 328 chip with the correct Arduino bootloader.

Currently the Arduino "system" supports ATmega328, ATmega168, and ATmega8 chips.  It does have to have a bootloader pre-installed, and you have to select an appropriate "board" in the tools menu.  If you put an Atmega8 in an Arduino Uno board, you should tell the IDE that you have an "NG or older with atmega8" (the "board type" has more to do with the chip and the  bootloader than it has to do with the rest of the board.)