Fuse restore ATtiny45 / ATtiny85. @ Home     Access count

Inspired by Dick Cappel "ATtiny12 fuse restorer" I created a almost same program for programming the ATtiny45 / ATtiny85 fuse bit RSTDISBL.

Using as many I/O lines as possible on a small AVR like the ATtiny45 / ATtiny85 you need to fuse the RSTDISBL fuse bit. That bit will enable the normal Reset input pin as a (almost) normal I/O line PB5. But there is a problem doing that, the in circuit programming (ISP) will not be possible after burning the fuse. So it is the last thing to do, if you want to reprogram the chip again!
To reprogram that fuse bit a special high voltage (12V) AVR programmer is needed, I do not own that kind of programmer. So I found the page of Dick Cappel to do the same for the ATtiny12 chip. I build that one and changed the source for use by the ATtiny45 / ATtiny85. For my wire-print I changed the I/O lines from the ATtiny2313 host cpu and added 3 input to select the default fuse bits, my own most used fuse bits open and closed fuse bits. I also changed the AT90S1200A to the (more recent chip) ATtiny2313 that also need no external crystal (and I have some of the cpu's at home). For the fuse bits I use lFuse = 0x64, hFuse = 0xDF and eFuse=0xFF (it is the chip default, 8MHz internal RC + divide by 8).
You will need to check the table-2 (or the .c file) for the connection, it is different as the picture of Dick show's!

For the 12V power adjustment (only a 9V battery is needed) please check the page of Dick Cappel, you only will have to do that ones.

Table-1 : Configuration jumpers
The jumpers can be used to select one of the three possible functions. The jumpers are going to ground and need no pullup resistor. The pin USRP2 is not used on the moment! 
X = Connected to ground
- = Not connected
Configuration jumpers
Comment
Fuse bits
USRP1
USRP2
USRP3
Low
High
Ext.
X
-
-
 Lock the chip.
0xE1
0x5D
0xFF
-
-
-
 Unlock the chip.
0xE1
0xDD
0xFF
-
-
X
 Erase and factory default fuse bit settings.
0x62
0xDF
0xFF
Table-2 : Hardware wire connection.
I did make the connections on the tiny2313 different then the schema of Dick shows.

Connection ATtiny2313 and ATtiny45 / ATtiny85
ATtiny2313
ATtiny45 / ATtiny85
Comment
PB0
12
O
PB0
5
I
SDI, Serial Data Input
PB1
13
O
PB1
6
I
SII, Serial Instruction Input
PB2
14
O-I
PB2
7
I-O
SDO, Serial Data Output
PB3
15
O
PB3
2
I
SCI, Serial Clock Input
PB4
16
O
VCC
8
I
5V Power
PB5
17
O
*PB5
1
I
/RST, Pull taget reset to ground
PB6
18
O
*PB5
1
I
+12V, Pull target reset to +12V
PD2
6
I
-
-
-
HEADER 1, Lock or unlock command
PD3
7
I
-
-
-
HEADER 2, Not used
PD4
8
I
-
-
-
HEADER 3, Erase the chip and fuse to factory default
PD6
11
O
-
-
-
LED Status code
Software download.
V0.1 at 05/02/2009: First release.

Download the AVRStudio project Fuse Restore ATtiny45 V0.1.zip.
Download the C source FuseRestore.c.
Download the ATtiny2313 hex file FuseRestore-ATtiny2313.hex.
Download the AT90s2313 hex file FuseRestore-AT90s2313.hex, you need to add a crystal to the cpu!

Examples.
Examples of other people building the fuse restore programmer.

Ken, K9FV Ken, K9FV

If you have a picture of your own build, and want to show it, mail the picture to me and I will put it on the website.
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