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tinyJTAG is a modification of the USBasp project to program via JTAG
instead of SPI or TPI, and to run on the ATtiny85.  

tinyJTAG is distributed under the terms and conditions of the GNU GPL version
2 (see "firmware/usbdrv/License.txt" for details).


All 6 IO pins of the ATtiny85 are used, including the reset pin.  The 
RSTDISBL fuse needs to be programmed to disable external reset funcionality
and enable use of the reset pin as IO.  After programming the fuse the part
can only be programmed through a high-voltage programmmer, or through the 
USBaspLoader-tiny85 boot loader.  The project is intended to be used in
conjunction with the USBaspLoader-tiny85 boot loader, and so doesn't include
an easy way to disable the external reset fuse in the makefile.  The 
USBaspLoader-tiny85 boot loader should be loaded on to the part first, tested
to make sure it was flashed properly, then the reset fuse can be disabled and 
the tinyJTAG firmware loaded through AVRDUDE.

If loading the the precompiled binary with bootloader, the bootloader will identify itself as a USBasp
programmer with an ATtiny85 target for five seconds before starting the 
tinyJTAG programmer, which will identify itself as a USBasp programmer.  
Wait for five seconds after connecting the tinyJTAG programmer to USB before
using AVRDUDE to connect to the JTAG target.  Be especially cautious when programming
ATtiny85 targets that you are connected to the tinyJTAG application and 
not the bootloader, as you could inadvertently erase the tinyJTAG application.

Set the fuses and load USBaspLoader-tiny85 onto the tiny85 using your programmer of choice
- "make fuses" and "make flash" in USBaspLoader-tiny85\firmware directory
Verify that the boot loader was loaded correctly and that AVRDUDE can connect to it
- a signature read in AVRDUDE should show the ATtiny85 fuses
When you're sure you're ready, disable the external reset fuse on the tiny85
- see "CAUTIONS" in the USBaspLoader-tiny85 project
- "make disablereset" in USBaspLoader-tiny85\firmware directory
Load the tinyJTAG firmware
- "make flash" in tinyJTAG/firmware directory

There are no jumpers that need to be set for programming with an external programmer



For more information on the tinyJTAG programmer, please visit the
following URL:

(c) 2012 Louis Beaudoin

Below is the unmodified README file for USBasp:


This is the README file for USBasp.

USBasp is a USB in-circuit programmer for Atmel AVR controllers. It simply
consists of an ATMega88 or an ATMega8 and a couple of passive components.
The programmer uses a firmware-only USB driver, no special USB controller
is needed.

- Works under multiple platforms. Linux, Mac OS X and Windows are tested.
- No special controllers or smd components are needed.
- Programming speed is up to 5kBytes/sec.
- SCK option to support targets with low clock speed (< 1,5MHz).
- Planned: serial interface to target (e.g. for debugging).


USBasp is distributed under the terms and conditions of the GNU GPL version
2 (see "firmware/usbdrv/License.txt" for details).

USBasp is built with V-USB driver by OBJECTIVE DEVELOPMENT GmbH. See
"firmware/usbdrv/" for further information.


This package includes a circuit diagram. This circuit can only be used for
programming 5V target systems. For other systems a level converter is needed.

The firmware dosn't support USB Suspend Mode. A bidirectional serial
interface to slave exists in hardware but the firmware doesn't support it yet.


Flash "bin/firmware/usbasp.atmega88.xxxx-xx-xx.hex" or
"bin/firmware/usbasp.atmega8.xxxx-xx-xx.hex" to the used controller with a
working programmer (e.g. with avrdude, uisp, ...). Set jumper J2 to activate
USBasp firmware update function.
You have to change the fuse bits for external crystal (see "make fuses").
# TARGET=atmega8    HFUSE=0xc9  LFUSE=0xef
# TARGET=atmega48   HFUSE=0xdd  LFUSE=0xff
# TARGET=atmega88   HFUSE=0xdd  LFUSE=0xff

Start Windows and connect USBasp to the system. When Windows asks for a
driver, choose "bin/win-driver". On Win2k and WinXP systems, Windows will
warn that the driver is is not 'digitally signed'. Ignore this message and
continue with the installation.
Now you can run avrdude. Examples:
1. Enter terminal mode with an AT90S2313 connected to the programmer:
   avrdude -c usbasp -p at90s2313 -t
2. Write main.hex to the flash of an ATmega8:
   avrdude -c usbasp -p atmega8 -U flash:w:main.hex

Setting jumpers:
J1 Power target
   Supply target with 5V (USB voltage). Be careful with this option, the
   circuit isn't protected against short circuit!
J2 Jumper for firmware upgrade (not self-upgradable)
   Set this jumper for flashing the ATMega(4)8 of USBasp with another working
J3 SCK option
   If the target clock is lower than 1,5 MHz, you have to set this jumper.
   Then SCK is scaled down from 375 kHz to about 8 kHz.


To compile the firmware
1. install the GNU toolchain for AVR microcontrollers (avr-gcc, avr-libc),
2. change directory to firmware/
3. run "make main.hex"
4. flash "main.hex" to the ATMega(4)8. E.g. with uisp or avrdude (check
the Makefile option "make flash"). To flash the firmware you have
to set jumper J2 and connect USBasp to a working programmer.
You have to change the fuse bits for external crystal, (check the Makefile
option "make fuses").

Software (avrdude):
AVRDUDE supports USBasp since version 5.2. 
1. install libusb:
2. get latest avrdude release:
3. cd avrdude-X.X.X
5. configure to your environment:
   ./bootstrap (I had to comment out the two if-blocks which verify the
                installed versions of autoconf and automake)
6. compile and install it:
   make install

Notes on Windows (Cygwin):
Download libusb-win32-device-bin-x.x.x.x.tar.gz from and unpack it.
-> copy lib/gcc/libusb.a to lib-path
-> copy include/usb.h to include-path
cd avrdude
./configure LDFLAGS="-static" --enable-versioned-doc=no

Notes on Darwin/MacOS X:
after "./configure" I had to edit Makefile:
change "avrdude_CPPFLAGS" to "AM_CPPFLAGS"
(why is this needed only on mac? bug in

Notes on Linux:
To use USBasp as non-root, you have to define some device rules. See
bin/linux-nonroot for an example.


Readme.txt ...................... The file you are currently reading
firmware ........................ Source code of the controller firmware
firmware/usbdrv ................. AVR USB driver by Objective Development
firmware/usbdrv/License.txt ..... Public license for AVR USB driver and USBasp
circuit ......................... Circuit diagram in PDF and EAGLE format
bin ............................. Precompiled programs
bin/win-driver .................. Windows driver
bin/firmware .................... Precompiled firmware
bin/linux-nonroot ............... Linux device rule file


For more information on USBasp and it's components please visit the
following URLs:

USBasp ..........................

Firmware-only V-USB driver ......
avrdude .........................
libusb ..........................
libusb-win32 ....................

2011-05-28 Thomas Fischl <>