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AVR usbisp stops working after i power the microcontroller

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jayanthyk192

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Hi,

I just built an AVR ISP programmer. I got it working and wrote a program on an ATMEGA128. I'm running this microcontroller off an SMPS(from an old comp.) I switched off the SMPS and after a few minutes switched ON the power. This rendered the USBISP to not work. Then i reconnected the USBISP and again it worked. Then I restarted the SMPS and again I had the same problem. I Tried this many times and had the same problem. What might be the problem? Please help.

Thank you.
 

The problem is with usbasp. You should connect usbasp after powering up the micro.
 

nandhu015 said:
The problem is with usbasp. You should connect usbasp after powering up the micro.
Click to expand...

What is the reason behind this? I could add something inbetween to stop this. I need to switch ON and OFF the MC.
 

You can try a buffer between usbasp and microcontroller.
 

nandhu015 said:
You can try a buffer between usbasp and microcontroller.
Click to expand...

I'm sorry, I forgot to update the thread. I tried it with a battery and it worked fine. So I added a switch inbetween the SMPS power line and MC. Now it's working fine. I even noticed that the usbasp goes into high impedance or input mode as any good programmer should. So I think the SMPS was giving a spike which made the usbasp to sleep or shutdown.
 

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