As I read this forum, I occasionally encounter people mentioning to beware of turning Atmel MCU into a brick with wrong fuse value. Since the consequences are so terrible, may I ask what are the things to look out for to manage this risk?
One thing I can think is never use RESET pin as PIO because ISP programming will be disabled. Can the more experienced members add more?
Will choosing the wrong kind of clock source brick a MCU?
AFAIK, you can't completely "brick" an AVR chip.
If you set the RSTDISBL fuse, you can recover if you have a high-voltage parallel programmer. These are pretty rare there days, though. So this is probably the more serious problem.
If you set the clock source wrong, you may need to inject a clock to get to a point where you can program the chip "normally." This is relatively easy, but certainly non-trivial. (for instance, if you have an SMT arduino, the pin that you need to inject the clock into a pin that is only connected to some rather small components. Not impossible, not as difficult as doing HV parallel programming, but probably more than enough to leave the average arduino user with a dead board...)
lightaiyee:
Will choosing the wrong kind of clock source brick a MCU?
Not brick it, but if you don't have an external clock you might need to add one until you reset the fuses.
lightaiyee:
One thing I can think is never use RESET pin as PIO because ISP programming will be disabled. Can the more experienced members add more?
I think that's the only really bad one.
Just to give you an example of bricking a chip.
During the last week I have managed to brick a ATtiny85 at least 5 times.
What I was trying to do was setting the fuses to use an external 32.768 x-tal.
The result was that the tiny was not responding to the programmer, it could not read the device signatur, so for me it was bricked.
What I did was using this simple HV programmer:
http://www.rickety.us/2010/03/arduino-avr-high-voltage-serial-programmer/
Worked every time
Erni:
What I was trying to do was setting the fuses to use an external 32.768 x-tal.
The result was that the tiny was not responding to the programmer, it could not read the device signatur, so for me it was bricked.
When you run the clocking down that slow, you will need an ISP programmer that can also slow down the sck clock enough. For my AVRISPmkII, I need to set it down to a 4KHz sck clock to program an ATtiny13A @ 16KHz. I use the avrdude -B250 option for that.
Hi hiduino,
Yes I know I probably have a problem with slowing down the clock on my programmer
I have used your advice from here
http://forum.arduino.cc/index.php?topic=89781.msg1235461#msg1235461
and the -B250 option too, so I guess I must use another programmer.
I am using TinyISP which have an option for slowing down the clock, it workes OK for Attiny13 at low clockspeeds.
It also could be the fact that my clock x-tal is not oscillating, so I will keep on experimenting.
Anyway, thanks for the advice
Erni:
It also could be the fact that my clock x-tal is not oscillating, so I will keep on experimenting.Anyway, thanks for the advice
You can use another Arduino to generate a clock signal for unbricking/experimentation.
You can use another Arduino to generate a clock signal for unbricking/experimentation.
Yes that's certainly a possibility
I don't want to hijack this subject, so I will start a new thread if my experiments fail