STK500 forget target voltages.

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sparrow2
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Posted by sparrow2: Wed. Sep 17, 2014 - 02:46 PM
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I have a "real" STK500

I normally use 5V and there everything is fine.

But now I have a 3.3V LCD, so I set target voltage to 3.3V , and that is fine.

But when I power cycle the STK500 it goes back to 5V is that normal? (the back light on the LCD turns blue at 5V!, I hope the LCD still is ok). 

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AVR Microcontrollers, megaAVR and tinyAVR
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Bronze Markjs
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Posted by js: Wed. Sep 17, 2014 - 09:02 PM
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But when I power cycle the STK500 it goes back to 5V is that normal?

It SHOULDN'T be but it is, at least that's my experience. I reported this a long time ago but I don't think anyone replied, happy to know someone else has the problem...... devil

 

By the way which version of Studio are you using?

John Samperi

Ampertronics Pty. Ltd.

https://www.ampertronics.com.au

* Electronic Design * Custom Products * Contract Assembly

Last Edited: Wed. Sep 17, 2014 - 09:10 PM
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Bronze Markjs
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Posted by js: Wed. Sep 17, 2014 - 09:05 PM
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Found thread from 2011 https://www.avrfreaks.net/forum/s...

John Samperi

Ampertronics Pty. Ltd.

https://www.ampertronics.com.au

* Electronic Design * Custom Products * Contract Assembly

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sparrow2
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Posted by sparrow2: Wed. Sep 17, 2014 - 09:25 PM
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ok thanks

So what was the conclusion?

It should but don't !

I have a newer and a very old board (one with a data flash on) I will try tomorrow.

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Bronze Markjs
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Posted by js: Thu. Sep 18, 2014 - 06:22 AM
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So what was the conclusion?

Don't use at < 5V?? laugh There is something screwy going on. From memory I removed the voltage adjusting pin coming from the main controller and replaced it with a pot and I still had voltages changing problems.

 

Maybe we need to replace the regulator with something better and have a simple 3.3V or 5V VCC selection via a switch???.

John Samperi

Ampertronics Pty. Ltd.

https://www.ampertronics.com.au

* Electronic Design * Custom Products * Contract Assembly

Last Edited: Thu. Sep 18, 2014 - 06:21 AM
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sparrow2
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Posted by sparrow2: Thu. Sep 18, 2014 - 08:40 AM
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Ok

The quick hack is 3 1N4007 to replace the vtarget jumper :)

It make 2.8 V, the back light is a bit weak but it's ok for test, and the controller work down to 2.6V  

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Bronze Markjs
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Posted by js: Thu. Sep 18, 2014 - 09:13 PM
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One of the 3 diodes can be a SCHOTTKEY type and you will save about 0.5V.

John Samperi

Ampertronics Pty. Ltd.

https://www.ampertronics.com.au

* Electronic Design * Custom Products * Contract Assembly

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