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Author Topic: Homemade Atmega328P-AU programmer  (Read 2988 times)
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South East USA
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I read where someone put the bootloader on their SMD Atmega328P by just manually pressing/holding it on pads while the bootloader loaded.  I made this little board to do this, but before I add it to my next BatchPCB order, I had 2 questions.

I designed it where I could just plug it into pins 8 thru 13 on my UNO.  Will pins 8 and 9 supply enough current to do this task?  8 will be the ground, 9 will be +5 volts.

Also, if the connection fails during the bootloading process, does that 'brick' the chip?

thanks,

ps.  All the components (caps, crystal, and a test LED-to verify success via the blink sketch) will be soldered to the board.  Only the Atmega328P-AU will be left blank, to manually hold the chip on and bootload it.


* Screen Shot 2013-04-13 at 2.18.38 PM.png (31.94 KB, 847x500 - viewed 80 times.)

* Screen Shot 2013-04-13 at 2.18.54 PM.png (41.54 KB, 517x529 - viewed 53 times.)
« Last Edit: April 13, 2013, 02:27:19 pm by SouthernAtHeart » Logged

Rapa Nui
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I would add a decoupling cap to VCC. Why the LED is connected to the PD3?
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BHZ, MG, Brazil
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I find that so risky.

Not only the risk of any discharge from your body can ruin the chip, but any minimal vibration from your hand can ruin the process.

I understand that a QFP32 socket is very expensive (shouldn`t be), but are you really willing to that that risk?
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Dallas
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Were I in your shoes I would...

• Get rid of the capacitor on AREF.  When burning a bootloader it serves no useful purpose.

• Follow pito's advice.  Get some decoupling capacitors on those power lines.

• Drop the crystal + capacitors.  I would use a clock signal from the programmer (are you using ArduinoISP?) instead.  Less soldering.  Fewer things that can go wrong.  Easier to fix if something is wrong.

• Have holes drilled around the target's corners so I could potentially put in "pillars" to keep the target aligned.

• Include a sketch with the bootloader that blinks the LED on PD3 as confirmation that bootloading worked.


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Will pins 8 and 9 supply enough current to do this task?  8 will be the ground, 9 will be +5 volts.

There have been various problems reported on the forum when VCC / GND pins were left unconnected.  I suggest making a valiant effort to get them all powered.
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South East USA
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Thanks for the feedback.  I'll update my design a little and try it out.
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Wahiawa, Hawaii
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I designed it where I could just plug it into pins 8 thru 13 on my UNO.  Will pins 8 and 9 supply enough current to do this task?  8 will be the ground, 9 will be +5 volts.

I think he means he wants to power the jig via the Uno (ArduinoISP) pins 8 and 9.  Probably not recommended.

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Dallas
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I think he means he wants to power the jig via the Uno (ArduinoISP) pins 8 and 9.

Ah, clever.

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Probably not recommended.

Why not?  I can't find anything in the datasheet to contradict that.  The highest number I can find for current consumption is 9mA.
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Wahiawa, Hawaii
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I guess that would make it very convenient since it’s small and compact to just plug the board into the Uno headers with just the 6-pins.  Yes, that is clever.

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Denmark
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An alternative:

http://www.hobbyking.com/hobbyking/store/__27195__Atmel_Atmega_Socket_Firmware_Flashing_Tool.html

I have not tried it, and it seems a litle expensive
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South East USA
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Edited my layout a bit, and will see how it works.  Yes the diode is for testing purposes, so I know it's flashed before soldering it on an important board.  I first designed it to sit inside the perimeter of the UNO, but then changed it so it sets on pins 8 thru 13, on the outside, with the chip on the very outside of the little 1" square board.  I have a tiny spring clamp, about like a clothes pin, I can clamp the chip on with that, visually inspect it for squareness, and flash away. 
I'll let you know how it works in about a month.

* Atmega328P-AU_Prgmr.brd (39.76 KB - downloaded 12 times.)
* Atmega328P-AU_Prgmr.sch (107.04 KB - downloaded 14 times.)

* Screen Shot 2013-04-14 at 10.18.11 PM.png (33.88 KB, 899x535 - viewed 50 times.)

* Screen Shot 2013-04-14 at 10.18.54 PM.png (25.77 KB, 405x484 - viewed 46 times.)
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Are the six through-hole pads meant to be aligned?
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South East USA
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Yes. If it works, ill post more photos.
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Just so you know ... in the image you posted every other pad is aligned.
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Are the six through-hole pads meant to be aligned?

https://www.sparkfun.com/tutorials/114
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Clever.  I'll have to modify (after searching) the six-pin ISP header.  Thanks.
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