Overclcok AtmegaL

You are so 3L33T. RaDiCaL To THe MaX, DuDe.

The JTAG might be holding down reset a bit longer than normal.

Remove JTAG, power up, use wire to reset device. Does it work?

Yeap, considering that they are plenty of Atmega16* at 16MHz, and cheaper than 8MHz as well.

If you overclock a 16MHz part to 32MHz, that might be intereresting.

I add RC at the reset pin which are 1M Ohm and 0.1uF respectively. But it has no improvement and is stll not working.

And I hot plug the USB cable after reset.

Don't do it. Use a faster processor instead

OK after adding 10uF decoupling cap at 3.3.V supply

i suggest you run a test over the complete temperature range.

It might run overclocked at 25 degrees ,but may fail in a hot summer. Bad practice if you want a stable sytem.

Johan

What size cap did you have there before? And another question - what sort of power supply are you using - better stated maybe, how long are the wires that bring power to microcontroller?

Neccessary filtering for a power supply always seems questionable.

Hul

eeh wrote:

Before that I used only two 0.1uF at the regulator. The board is small which is about 3 inches x 2 inches. The power supply is dc supply (5V) and the voltage passes a HT7533 linear regulator.

Oh I see. Could you teach me how can I do that if I have no temperature chamber?

Use a hair dryer. Cautiously.

Ice chest, light bulb,cold packs, thermometer. You are over clocking a micro. Be creative.

Or a cardbord box. If your device dissipates enough heat it will warm up all by it self. Otherwise add a little heat somewhere, possibly with the above mentioned testing equipment. ;-) Oh and keep an eye on the temperature, you don't want to start a fire.

Most household ovens can be set as low as 50 degrees C, but check with a thermometer.

And there are many other sources of suitable heat in most houses, so experiment a little.

And you may want to check in the cold as well. fridge, freezer, cold spray, outside.....