Programming surface mount AVRs without an adapter?

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I am designing a small single-sided board and would like to use a surface mounted AVR controller, but I have run up against a small problem:

To date, I have only used DIP parts and I don't have any way of programming surface mount parts out of circuit.

I have come up with some potential solutions, but they are not appealing at all.

1. Lay out an ISP connector on the board, then saw off the connector after the chip is programmed. This would compromise the layout, which is a problem because there is RF circuitry right next to the controller, and

2. Solder very tiny wires from an off-board ISP connector to the chip. Not a much better solution given that I might have to use a TQFP package (and my hands aren't as steady as they were when I was 20).

So...why don't I just buy a programming adapter? Because I am very tight and if I did want to spend the money, there doesn't seem to be a place to get one here in upcountry Thailand,

I know there are some pretty experienced and creative people on this forum, so I thought it worth posting here to see if anybody here had any good ideas.

Thank you in advance for considering my problem.

--
"Why am I so soft in the middle when the rest of my life is so hard?"
-Paul Simon

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If you can scrounge a spring-loaded SIP header from an old PC case or the like, or maybe even a zebra strip, you could hold it against bare programming pads on the board.

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Or ... you could add some edge connector pads to your layout and plug your board into a mating edge connector socket. Its been suggested before so the kudos goes elsewhere...

Ross McKenzie ValuSoft Melbourne Australia

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Quote:

Lay out an ISP connector on the board, then saw off the connector after the chip is programmed.

Why not leave the connector in place?

If you think education is expensive, try ignorance.

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Or, use a 2x3, 6-pin header that is designed for surface mount.

In fact, I've taken SIP headers that were right angle, removed the pins, and then put them in a 2x3, 6-pin thru-hole header (first removing the straight pins from the 2x3 header, of course). Walla! You now have a 2x3, 6-pin SMT header. It only takes a couple of minutes do make the conversion.

You can avoid reality, for a while.  But you can't avoid the consequences of reality! - C.W. Livingston

Last Edited: Sun. Sep 14, 2008 - 02:55 PM
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Could you bring the TXD/RXD lines of the UART out to a couple of pads? In that case you could maybe use a botloader rather than ISP though you obviously need some way to get a squirt of the bootloader into the chip in the first place - maybe program the chips in a TQFP socket before they are mounted?

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Have you tried eBay?
I picked up a couple of lever-top SOIC-8 sockets a couple of months ago for less than £5.
Be aware that there are wide-soic and narrow-soic chips. The Tiny13's I've got are wide SOIC-8 and I had to use my needle-files on the adapter before the T13s would fit in.

For a heath-robinson solution, could you mount a pair of 4-finger boards onto a clothes-peg or similar?

[edit:typos]

Nigel Batten
www.batsocks.co.uk

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Wow - those are some great ideas. I can see that I will be able to get those chips programmed one way or the other. First off: finding a calculator with an LCD that I can sacrifice to get that zebra strip! And there are plenty of great ideas as backups.

Thanks you all :)

--
"Why am I so soft in the middle when the rest of my life is so hard?"
-Paul Simon

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Glad to hear that your have some fertile areas for further exploration!

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Here's a photo of the world's first Montblanc programming adapter. Those are spring loaded PCB test pins spaced to fit a standard 0.100" ISP layout, but there is no reason why you can't use some of the smaller inspection pins and lay them out to fit the SMD chip package.

Attachment(s): 

Cheers,

Tom

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There is no need to put a connector into place. Simply draw the land pattern and during programming install the connector temporarily. Contact can be ensured by small bending force on the connector.

I have used 6 through-hole pads at 1.25mm pitch and a corresponding molex connector with great success..