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The Emul8or is a programming emulator for the AVR ATtiny85 microprocessor. It allows programming of the processor
without removing it from it's socket in the target system.

The Emul8or is designed to allow a convenient method of programming one of Atmel's smallest processors, the 8-pin ATtiny85. Programming of these chips requires the use of at least 4 pins (5 for high-voltage programming) so with only 6 IO pins available on the ATtiny85 it is guaranteed that the programmer will clash with the application and possibly try to drive signals that may not be designed to be driven.

Thus programming of these small chips usually requires them to be physically removed from the target system, a procedure that gets tedious very quickly when developing.

Emul8or Mk I

The Mk I uses "logical" emulation, meaning that a functionally similar chip (the ATtiny861) is used to emulate the ATtiny85. While this means that some functions are slightly different (mostly dealt with by using conditional code blocks) the extra pins allow access to the outside world and therefore a method of displaying internal information for debugging.

The Emul8or Mk I has the following features.

  • Allows ISP programming with auto-detect.
  • A reset button to reset the target system.
  • A debug output that can be used to trigger external test equipment such as a logic analyser.
  • All six IO pins broken out for easy connection to external test equipment.
  • A virtual connection to a USB port to allow an internal monitor program to display data.
  • Application access to an LED for simple debugging output.

3D model of the Emul8or Mk I PCB.

The Emul8or Mk I has two processors, an ATtiny861 runs the application code and an ATmega328 controls the device and allows a monitor program resident on the emulating processor output to a terminal program running on a PC.


Emul8or Mk II

The Emul8or Mk II is a full "physical" emulation, meaning that it uses an ATtiny85 chip exactly the same as the chip used in the target application.

Programming is facilitated by isolating the processor pins. It has the following features.

  • Allows either low-voltage ISP or high-voltage programming.
  • Auto detect of low-voltage programming.
  • A reset button to reset the target system.
  • Access to pin 1 for a user reset function or Debug Wire debugging.
  • Total isolation of four programming data signals plus VCC and RESET/VPP.
  • Daisy-chaining of multiple Emul8ors.

3D model of the Emul8or Mk II PCB.


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PO Box 450, Gin Gin, QLD, Australia.