YO3BN - AVR USBTiny Programmer

Posted at - 5th July 2017
Last edited - 6th July 2017

AVR USBTiny Programmer

This programmer is based on FabISP programmer
Actually, it's a USB to ISP converter, using an ATTiny ucontroller
The USB transceiver is implemented in software by VUSB library emulating USB 1.1 device protocol
Easy programming procedure thanks to ZIF socket
Used in conjuction with the command "avrdude -c usbtiny ..."

Construction Details

The schematic is very simple, the ATTiny does almost entirely job. The two zener diodes trim the 5V pinout level from ATTinty to 3.3V USB standard. The two resistors R3, R5 forms a single 1.5K resistor which pulls up the D- line to inform the USB host that a low-speed device is connected to it. Two LEDs + 150 ohms were connected to pins 11 and 12 in my project in order to indicate some activity. I planned to modify the firmware for that, but the LED on pin 12 already worked by default.

The ZIF part was implemented on test PCB. When programming, male jump wires will be connected from programmer's pin header to AVR uController pins according to uController datasheet. Also, a 3.686MHz quartz and 2x15pF capacitors were provided for external clock requirements on the test PCB.

Pinout

Flat cable pinout

ZIF board pinheader

The Firmware

The firmware can be downloaded from my local image or from official sources on the internet. It must be recompiled with 12MHz crystal operation by editing Makefile and recompiling the sources.
This section will be continued in near future...

73 de YO3BN