AVR Freaks

Why was -F in my command line?  It's easy to explain.  When I started on my last project, about a year ago, it was my first ever contact with programming a microprocessor, so I was totally dependent on what I was told by those in the know - and I don't actually know anybody that does.  I learned what I could by reading websites about the AVR chip and how to program it.  The Instructables website, at

http://www.instructables.com/id/... ....  says ...

Open Atmel Studio 6.

Go to Tools>External Tools

Fill in the fields as the picture shows. The Command field is to be filled with the location avrdude in your machine, in my case: C:\Program Files (x86)\Arduino\hardware\tools\avr\bin\avrdude.exe

As to the Arguments field, fill in with the following line:

-U lfuse:w:0xe6:m -U hfuse:w:0xd9:m -e -F -v -patmega328p -carduino -PCOM2 -b19200 -D -Uflash:w:"$(ProjectDir)Debug\$(ItemFileName).hex":i -C"C:\Program Files (x86)\Arduino\hardware\tools\avr\etc\avrdude.conf"

At that point, I did not even realise that the command string was to be passed to AVRDude.  I thought it was a commnd to AS-7 to tell it what to do with the target.

Well, I learned those things along the way, but I managed to get my project made, and as I wasn't having trouble with the command string, I never queried it or changed it.  It seemed to work.

You guys have a lot of experience, so you spotted the -F right away.  I don't, and wouldn't have been able to. 

You're right about me being "an inexperienced driver about to do a maneuvre with my car that I'm no master of."  However, I have had instruction to click the anti-break-lock switch before I start.  Clearly, I need further help.  The field of microprocessors is so big that you might as well say to somebody who asks a question "Why don't you know this?  It's in Wikipedia!"  Also, I'm unlikely to kill myself or anybody else by using -F.  Before you are let loose in a car, you have to take a driving test.  Writing to this forum is, in many ways, my test - and if I am found wanting over and over, well, I learn bit by bit - but I really need help, not criticism.  Well, the -F has been pointed out, so I have looked it up, and will remove it from the string.

Now, if you'd suffer me to do so, I'd like to repeat my questions.

Q1 : would this (the RESET line being set as output) produce the effect I'm seeing?

Q2 : Has it really set the fuses to 00, or does it just think so because it is unable to pull the RESET line?

Q3 : Have I stuffed my chips?  I guess I can't even supply an external clock to a pin that is set as output.

If I have, they weren't very expensive, so it's not the end of the world - but I'd like to recover them if it's relatively easy.

Thanks, Johan,  I'll do that, and also give a link back to this thread.  Check the link again in a few minutes to see my update.  However, although this is one site that gives -F as a parameter, it's only one site.  That's where I got it from, but I'd bet there are plenty others.  For example, if I had been making a writeup somewhere of how I did my project (a soft-start for a 240V motor), I would probably have propagated that line because I wouldn't have known any better, so it is quite likely that there are other websites that give it.

Any ideas about my questions?

"You should not write about things you do not master. "

I didn't.

Soprry, should have mentioned...

"ISP now has to be 32kHz or less."

I think it must be, then, as it still programs the chip when those fuse settings are used - but it only programs it once.  After that, it is unprogrammable.

Thanks for this, but the programmer is working, and the chip is doing what I wanted.  The problem is that this is a project in process, so I will be reprogramming the chip several (possibly many) times, and at the moment, it only programs it once.

Let me give you an example.  When I decided to use a 128k clock, I wanted to check that that's what I was getting, so I set the fuses to 0xA4.  I checked the clock output and it was correct, so then I wanted to move on to the next stage.  I made a few mods to the program, but discovered I couldn't write them to the chip because of the error given above.  However, I still have that chip, and if I put it into the breadboard, it still gives me a 128K clock on pin 3.  The chip is still working, but I can't program it.  Now, having done a bit of reading and a bit of thinking, I thought it was because I set pin 1 (PB5) to an output in DDRB, so that would prevent the ISP from pulling its logic level, which would prevent it from programming the chip.  However, Brian Fairchild (#11) says "To use Pin1/PB5 as an output you have to disable the RESET functionality in the fuses", and I didn't do that - and I certainly didn't mess with RSTDISBL.

AHA!  Moment of enlightenment (?)

Brian also mentions the ISP clock, and it is only now, as I write, that the penny has dropped, that the chip was running with its native 1MHz clock the first time it was programmed, so I guess it is my clock frequency at fault.

I have been experimenting to establish what frequency the programmer is using.  I'm 'programming' an empty chip socket.  When AS-7 gets to the point of declaring that the fuse has gone to 00 - "Do you want to change it back?", I answer Yes, and it tries continually to do so, and I can look at the signals.

MOSI has a signal on it, but it's very jittery, and I can't make much sense of it

Pin 7 has a nice signal on it, however.  It shows a series of pulses, 4uS TRUE, 4uS FALSE (8uS/cycle = 125KHz).  The series lasts 250uS (probably 32 cycles), and repeats every 6mS

So it looks like my frequency is 125KHz, and Clawson already said it should be 32kHz or less.  I'll look at the -B option for AVRdude.  Thanks.

OK Guys, unless you have something more to say about it, I guess I know what I need to do.  And what not to do.

Thanks for all your help.

Incidentally, FYI, the application is for a 240V timer.  I have a tendency to leave my garage lights on, and not to discover it till next time I need the car, which can be a week.  I also leave my coffee machine on for hours at a time.  The timer will not have any display, but will be programmable with a single button for a number (1-65535) seconds.  Its readout is a beeper, and another pin drives a transistor that closes a relay.  I know that timers can be purchased, but it's a project.  I like doing little projects - and I have some spare AT85's.