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Diy grids fuse settings / timing confusion
MUFF WIGGLER Forum Index -> Music Tech DIY  
Author Diy grids fuse settings / timing confusion
Hello everyone. I just finished a diy grids build. Using an arduino as ICSP, I manually flashed the fuses to

lfuse:0xff hfuse:0xd6 efuse:0x05

Then flashed the hex file, which wrote and verified with no issues. Per the make file on Olivier's github, this is actually incorrect. hfuse should be 0xd8, so I then reset the fuses to

lfuse:0xff hfuse:0xd8 efuse:0x05

This gave me some trouble, with "programmer not responding" errors, so I was concerned that I had set fuses to look for an incorrect clock. Eventually I was able to reset the fuses though.

After all that, I found that the module seemed to be running extraordinarily slow, so I'm still worried that I have a clock issue. From a fuse calculator, it seems like those settings should be using an 8mHz external clock, but the clock I soldered on is 20mHz per the mutable schematic.

Do the fuses need to be reset to deal with the 20mHz clock after flashing the hex? Am I just confused by the clock resolution setting in grids? If I reduce the resolution to 4 ppqn, it seems to be working ok, but I'm still a little confused. If grids is set to 4ppqn, and I want a sequencer to change on quarter notes, then do I need to run the clock through a divider to make that happen?

Also, can anyone confirm that the fuse settings above are correct?
Hello, I made grids with a nano standard arduino 16mhz, flashed the hex first then the fuses like this:

-U lfuse:w:0xff:m
-U hfuse:w:0xd8:m
-U efuse:w:0xff:m

and there is no problem.
You can try with

avrdude -c avrispv2 -p m328p -P com3 -U flash:w:grids.hex -U lfuse:w:0xff:m -U hfuse:w:0xd8:m -U efuse:w:0xff:m -U lock:w:0x2F:m
Thanks for the info, it looks like the extended fuse 0xff vs 0x05 is just brownout disable, so I'll probably leave it be.

Does anyone know the reason for setting lock bits? I googled around and didn't see a clear breakdown. Worst case I suppose I could dig into the atmega328p datasheet, but I'm wondering if someone knows why it's a good idea to set them.
nickajeglin wrote:
After all that, I found that the module seemed to be running extraordinarily slow

Indeed if the fuses are set incorrectly, then the clock is slow.
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