Introduction: Simple and Cheap Fuse Doctor for Attiny
When you are working with Attiny's like the Attiny 85 or the Attiny13, it is bound to happen sooner or later: you brick your Attiny.
I got faced with it while trying to burn a bootlaoder (i.e. setting the correct fuses), that I suddenly got the dreaded 'Yikes! Invalid device signature' error message. As I had just succesfully burned it on IDE1.06 and now was trying on IDE1.6.3, just to see if I installed everything OK, I knew the chip was OK and that my programmer was OK. Also, a new chip did well, so something ominous must have happened to my chip.
Could it be because my computer had some memory problems during the burning???
Well, not much choice but to try and reset my Attiny85.
For that you need a Serial High Voltage Programmer. Plenty of circuits to find, so no way I claim to be original here, but I am writing this ibble to take away any hesitation that people might have by showing how quick and easy it is.
All it takes are 6 resistors, a transistor, a DIL foot, a 9x20 piece of stripboard and a 7-pins male header and of course a 12 Volt supply. And yes, A UNO to stick it in.
As I didnt expect to use the programmer very often, I planned to use a battery, but as I couldnt find my 12 Volt battery, I ended up using a 0.75 USD (so 75 dollarcents) 5 to 12 Volt converter from aliexpress, that i had for another project.
I used the program below. The program starts when you send a random character to teh serial port. As it turns out, it was a fuse problem in my chip as the fuse bits were E4 DF which means it was set for 128 kHz oscillator. Not sure how that could happen as I removed that choice from my menu in the boards.txt file.
Anyway, it reset the fuses to factory setting and after that I could use my Attiny85 again.
Sadly, in order to build this unbricker, I had to use the 1k resistors I wanted to use for the very project I was programming the Attiny for :-) Oh well!!
All in all took me less than an hour to put it together So if you are having problems with your Attiny13/25/45/85 build one of these.
If you want to unbrick the 24/44/84 series, you need a bigger DIL Foot.
If you are trying to unbrick an Attiny15.. then remember that that has PB3 and PB4 switched compared to the 13/25/45/85 series, so you probably need a software or hardware change (Tar and feathers for the Atmel designer who did this)
// AVR High-voltage Serial Fuse Reprogrammer<br> // Adapted from code and design by Paul Willoughby 03/20/2010
// <a href="http://www.rickety.us/2010/03/arduino-avr-high-voltage-serial-programmer/" rel="nofollow"> http://www.rickety.us/2010/03/arduino-avr-high-vo...</a><br> //
// Fuse Calc:
// <a rel="nofollow">http://www.rickety.us/2010/03/arduino-avr-high-vo....</a> #define RST 13 // Output to level shifter for !RESET from transistor
#define SCI 12 // Target Clock Input
#define SDO 11 // Target Data Output
#define SII 10 // Target Instruction Input
#define SDI 9 // Target Data Input
#define VCC 8 // Target VCC #define HFUSE 0x747C
#define LFUSE 0x646C
#define EFUSE 0x666E // Define ATTiny series signatures
#define ATTINY13 0x9007 // L: 0x6A, H: 0xFF 8 pin
#define ATTINY24 0x910B // L: 0x62, H: 0xDF, E: 0xFF 14 pin
#define ATTINY25 0x9108 // L: 0x62, H: 0xDF, E: 0xFF 8 pin
#define ATTINY44 0x9207 // L: 0x62, H: 0xDF, E: 0xFFF 14 pin
#define ATTINY45 0x9206 // L: 0x62, H: 0xDF, E: 0xFF 8 pin
#define ATTINY84 0x930C // L: 0x62, H: 0xDF, E: 0xFFF 14 pin
#define ATTINY85 0x930B // L: 0x62, H: 0xDF, E: 0xFF 8 pin void setup() {
pinMode(VCC, OUTPUT);
pinMode(RST, OUTPUT);
pinMode(SDI, OUTPUT);
pinMode(SII, OUTPUT);
pinMode(SCI, OUTPUT);
pinMode(SDO, OUTPUT); // Configured as input when in programming mode
digitalWrite(RST, HIGH); // Level shifter is inverting, this shuts off 12V
Serial.begin(19200);
} void loop() {
if (Serial.available() > 0) {
Serial.read();
pinMode(SDO, OUTPUT); // Set SDO to output
digitalWrite(SDI, LOW);
digitalWrite(SII, LOW);
digitalWrite(SDO, LOW);
digitalWrite(RST, HIGH); // 12v Off
digitalWrite(VCC, HIGH); // Vcc On
delayMicroseconds(20);
digitalWrite(RST, LOW); // 12v On
delayMicroseconds(10);
pinMode(SDO, INPUT); // Set SDO to input
delayMicroseconds(300);
Serial.println("Reading: ");
unsigned int sig = readSignature();
Serial.print("Signature is: ");
Serial.println(sig, HEX);
readFuses();
if (sig == ATTINY13) {
writeFuse(LFUSE, 0x6A);
writeFuse(HFUSE, 0xFF);
} else if (sig == ATTINY24 || sig == ATTINY44 || sig == ATTINY84 ||
sig == ATTINY25 || sig == ATTINY45 || sig == ATTINY85) {
writeFuse(LFUSE, 0x62);
writeFuse(HFUSE, 0xDF);
writeFuse(EFUSE, 0xFF);
}
readFuses();
digitalWrite(SCI, LOW);
digitalWrite(VCC, LOW); // Vcc Off
digitalWrite(RST, HIGH); // 12v Off
}
} byte shiftOut (byte val1, byte val2) {
int inBits = 0;
//Wait until SDO goes high
while (!digitalRead(SDO))
;
unsigned int dout = (unsigned int) val1 << 2;
unsigned int iout = (unsigned int) val2 << 2;
for (int ii = 10; ii >= 0; ii--) {
digitalWrite(SDI, !!(dout & (1 << ii)));
digitalWrite(SII, !!(iout & (1 << ii)));
inBits <<= 1;
inBits |= digitalRead(SDO);
digitalWrite(SCI, HIGH);
digitalWrite(SCI, LOW);
}
return inBits >> 2;
} void writeFuse (unsigned int fuse, byte val) {
shiftOut(0x40, 0x4C);
shiftOut( val, 0x2C);
shiftOut(0x00, (byte) (fuse >> 8));
shiftOut(0x00, (byte) fuse);
} void readFuses () {
byte val;
shiftOut(0x04, 0x4C); // LFuse
shiftOut(0x00, 0x68);
val = shiftOut(0x00, 0x6C);
Serial.print("LFuse: ");
Serial.print(val, HEX);
shiftOut(0x04, 0x4C); // HFuse
shiftOut(0x00, 0x7A);
val = shiftOut(0x00, 0x7E);
Serial.print(", HFuse: ");
Serial.print(val, HEX);
shiftOut(0x04, 0x4C); // EFuse
shiftOut(0x00, 0x6A);
val = shiftOut(0x00, 0x6E);
Serial.print(", EFuse: ");
Serial.println(val, HEX);
} unsigned int readSignature () {
unsigned int sig = 0;
byte val;
for (int ii = 1; ii < 3; ii++) {
shiftOut(0x08, 0x4C);
shiftOut( ii, 0x0C);
shiftOut(0x00, 0x68);
val = shiftOut(0x00, 0x6C);
sig = (sig << 8) + val;
}
return sig;
}
