ISP MINI - yet another avr programmer

[c4757p]

I'm unimpressed with most of the open or cheap AVR programmers. They're either limited to SPI, or big chunky affairs with multiple headers and jumpers. Typically not very well protected. Okay, mostly I'm just pissed I blew my mkii clone by connecting it wrong. Wasn't protected well enough and the microcontroller itself blew up. Couldn't find a replacement I really liked, so I'm going to NIH this shit.

Here's my take on a small, open-hardware AVR programmer.

- Based on the existing LUFA mkii-clone firmware, I don't care to NIH that. Slightly modified, however.
- Supports SPI, TPI, PDI all out one connector, no messing around with multiple headers.
- Full target-powered level-shifting down to 1.2V to cover the full range of AVR voltages.
- Programming port is short-circuit and ESD protected. You should not be able to blow this up.
- Relatively small (40mm x 25mm); still built with nothing smaller than 0603.

Limitation: does not provide target power. I refuse to half-ass features, and there's no room in this design for proper target power will full protection as I would insist on having.

Known bug in rev 0: crystal footprint is too small. I stupidly assumed 12 MHz for the USB crystal, forgetting that the AVR USB by default wants 8 MHz. No 8 MHz crystals are available in that footprint. Workaround: solder leads of a PTH crystal to the pads. rev 1 will be fixed. I called it rev 0 for a reason.

Regardless of interest, I'll make this available soon as a shared OSH Park project and DigiKey BOM for anyone to build themselves. If enough people think my "improved" take on this is worth the effort to care about yet another AVR programmer, I will definitely consider selling them, either as kits or fully built units.

Possible future additon: ISP MAXI. Larger, more complete version. Full target power, slightly different (more 'proper') implementation of signal muxing, overcurrent protection also on ground. Considering features: JTAG to support non-AVR Atmel chips, storage for firmware images to allow for field programming, some user IO or at least UART to the target to allow batch testing after programming.

Currently the BOM cost is $16, in low quantity.

[c4757p]

Schematic and PCB renders are now in the git repository.

Schematic (rev0)
PCB (rev0)

Repository: cpavlina/ispmini

[c4757p]

Rev0 has been thoroughly tested and revised for rev1.

- Fix the DFU button, it didn't work.
- Make room for a full-sized crystal.
- Remove reverse-programming capability (connect another ISP device up its own port, for debug). Didn't work properly and isn't very important.
- Choose a proper case and reorganize the board to fit.

I'll have a bunch of boards made - anyone who wants a board and BOM, let me know. At the moment I'm not buying full parts or assembling, as I don't know how many people want them.

[lukaq]

looks small, very good

[c4757p]

The enclosure is a Hammond 1551NGY - cute little 35mm/1.4in square. (Alternatively, 1551NTBU which is translucent blue )

[alank2]

Looks cool c4757p.

I say forget powering the target - that is the target's job!

[Ysjoelfir]

Nice little board! If the shipping to germany wouldn't probably cost a fortune, I would be quite interested in one of those boards.

[c4757p]

Looks cool c4757p.

I say forget powering the target - that is the target's job!

Thanks.

Indeed, which is why I didn't really bother on this - it's a cool thing to have in a select few cases, but not really something I need. It's something I'd expect on a "full-featured" programmer, but nothing smaller than that.

[georges80]

Nice job, but I'm happy enough with Atmel's own little USB programmer. Cheap enough, fully supported and a small mod to add a little regulator board and a switch and it can provide target power (or not) for my boards.

I need target power since I program 100's of small boards at a time and having a single pogo pin based adapter that powers the board during programming is an essential feature to streamline the process.

For any debugging etc I use a ONE which was on sale a couple of years back for $200. Nice for debugwire debugging.

cheers,
george.

[c4757p]

Fair enough, I can see how that's useful for you

I'm still considering doing a larger version in the future with all of that, except of course being supported by Atmel - obviously, if you can afford the official ones they're nice to have, but the good stuff is still a bit pricey.

Wonder if I could figure out how to get one debugging.