USB Circuit Diagrams

Simple USB AVR-ISP Compatible Programmer Schematic Circuit Diagram

The Challenge of Outdated Ports for Microcontroller Enthusiasts

In contemporary PCs, the absence of serial or parallel ports poses a significant obstacle for enthusiasts experimenting with microcontrollers. In the past, utilizing a standard PC’s parallel port made programming various AVR microcontrollers straightforward. However, in the present scenario, individuals interested in this pursuit are compelled to invest in a programmer that connects to the PC via USB. This requirement substantially raises the entry barrier for newcomers wanting to engage with these microcontrollers.

Innovative Circuit: Overcoming USB Interface Challenges

The circuit introduced here provides a viable solution to the USB interface dilemma. Examining the schematic, it becomes evident that this is a remarkably uncomplicated setup, revolving around an affordable standard AVR microcontroller and a few passive components. Notably, this microcontroller lacks a built-in USB interface, and the circuit doesn’t rely on a USB to serial converter either. The circuit’s strength lies in its firmware. The USB interface has been ingeniously implemented in software, a technique elucidated in our previous article ‘AVR drives USB,’ featured in the March 2007 issue.

Simple USB AVR-ISP Compatible Programmer Schematic Circuit Diagram

Efficient Firmware Integration: Mimicking AVRISP Programmer

The firmware plays a crucial role in ensuring that the circuit functions seamlessly as a serial port, enabling it to establish communication with AVR Studio, Atmel’s standard development environment. Through this ingenious implementation, the circuit behaves as an authentic AVRISP programmer, fostering compatibility and ease of use.

Simple Circuit Construction and Essential Configurations

This circuit’s simplicity allows for easy assembly on a small prototyping board or a breadboard, facilitated by the availability of the controller in a DIP-28 package. For those planning to program the controller via connector K2, it’s imperative to configure the fuses correctly. Specifically, the internal oscillator must be configured to employ the external crystal as the clock source. Additionally, jumper K3 is included to power the circuit to be programmed via the USB port. Although it’s advised against due to potential complications. Notably, K4, a 10-way box header, follows the standardized pinout used universally by Atmel, ensuring consistency in its connectivity.


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