EED2 Project Underway

DigiTan · Posted: 16 Jun 2005 02:14:45 pm Post subject:

Yeah, I'll put the plans on my webpage along with the previous version.

Yesterday I finally finished the part I've been dreading where the flash chip gets soldered to the circuit board. This is almost impossible to do by hand with any reliability. The chip seems to have some heat damage from all the corrections and re-corrections I had to make because of the solder jumping onto unwanted pins.

I'll test it later this evening to see if it is undamaged. If not, I can start interrogating the chip and build the first load/save routines. Luckily, this manual task was the hardest part of the whole project and I ordered a backup chip in case this one was fried.

thecheatscalc · Newbie Joined: 08 Jun 2005 Posts: 29

what about the board? i've tryed soldering on a circut board and the circut board came out uhhh messed up as well as the hardware that i was trying to put in but at least I was just messing around. you aren't

kermmartian · Posted: 17 Jun 2005 03:38:30 pm Post subject:

Good luck with this, I know how hard it is to solder tiny ICs accurately. Smile

DigiTan · Posted: 18 Jun 2005 01:03:53 am Post subject:

Yep, the stuff's a huge pain. Luckily, it's possible to do this with a solder paste and a 400º toaster oven but I don't have either of those available. So far the initial tests are okay and I'm a few minutes away from doing a reset test.

agility · Posted: 28 Jun 2005 05:03:18 pm Post subject:

This might aid you in soldering: Numbnut's guide to soldering Surface Mount devices

DigiTan · Posted: 29 Jun 2005 05:52:03 pm Post subject:

Thanks! Yeah, this was another technique discribed to me in a forum. It looks pretty promising even with these small pitches. My first try seemed to fry the chip, and it acts like it's stuck in the reset state. I'll try this with my 'backup' chip and hopefully have some success.

wrigley · Advanced Member Joined: 19 May 2004 Posts: 399

if you buy a socket for your chips you only dont need to worry about overheated chips, I'd suspect sockets to be cheaper to wreck, should it go wrong. besides, you can easily change the chip later

DigiTan · Posted: 04 Jul 2005 03:02:19 pm Post subject:

I'm also hoping a temp heatsink will help keep it cool next time. Before, I tried spraying R-134a refridgerant on it, but I don't have 3 hands for that. The chip for now is going on one of those "surfboards" that will plug into a typical breadboard. I'm pretty confident it will work next time, so I'll try it tonight...after fireworks, of course.

aforsy · Posted: 09 Jul 2005 01:50:39 pm Post subject:

any progress recently?

DigiTan · Posted: 11 Jul 2005 03:15:18 am Post subject:

Eh, not too much lately. I'm stuck trying to cram in a ton of other projects before school starts. One of them is a larger version of that Calc Guardian idea I mentioned earlier. It's pretty weird-lookin', but I'm hoping it'll be done on the 15th. ...The calc guard anyway.

DigiTan · Posted: 23 Jul 2005 03:32:57 am Post subject:

Well, I have some very bad news. Yesterday I tried to solder my backup chip to the same type of surfboard using the new methods. At first, it went exactly as the webpages decribed, but after testing--I discovered that only 5 of the 8 pins were actually making contact. The rest were not making contact for reasons I can't explain. Also, all of my (clean) solder kept turning into a black fouling crud. The board itself was also covered in invisible flim that obviously doesn't conduct electricity either. After hours of correcting this, I quit and flushed the whole thing.

The SMT soldering isn't worth the cost or frustraition put in, so as of this week, I'm decomissioning the project. This means it's cancelled and all the parts I ordered for it are going in other devices.

For now I'm focusing on finishing the Calc Guardian project and improving the EED1. I might consider reviving this project, but frankly the soldering has been one huge waste of time, and I'd need to hire someone to do the SMT soldering before any more work could be done. Luckily, the 4Mb chips were cheap, but I don't plan to ever try this again unless I can find a method that actually works. Since the plans were already drawn up, I'll keep those up on the webpage...

Raster · Active Member Joined: 17 May 2004 Posts: 529

Now a days, the solder and soldering tips are sh@t...

DigiTan · Posted: 29 Jul 2005 01:56:59 am Post subject:

Well, I've been talking to some other techs and it looks like it was the glue that killed this last run. I may try this one last time but either way it'll be a while because I left my etching stuff up-state.

For now I'm diverting parts to the Calc Guardian project, and the larger variant of this is already in the construction phase.

DigiTan · Posted: 28 Sep 2005 08:56:09 pm Post subject:

Okay, here's the scoop. I'm in the process of repairing the busted linkport on one of my TI-82s to try to finally get a program onto my calc. Long story short, as part of this, I'm going to try an revive the EED2 project.

As step #1 in the revival, I'm going to ripup the last design and make a few changes. For starters, both the control chip and the 4Mb archive will be surface-mounted to save space. The king-sized voltage regulator is being replaced with a low-power design that will avoid draining the batteries when the EED2 is turned off. And finally, the huge relay is being replaced. "Replaced with what?" I don't know, I just know it's too large and very troublesome.

For ease-of-use purposes, I'm keeping the original version on file, because its a lot easier to build without specialized parts. The new one might also have a reading light feature, if that isn't too flashy. ...Er...no pun.

Andy386 · Newbie Joined: 18 Jun 2006 Posts: 1

its a great idea, the circut seems to be working, its complex enough Smile

but i'm wondering how you would make your TI-82 to recive Files from the flash ?
Reciving variabels are working, but wholes dosen't, i thougt.
making a acht client is easy, but how would you implement the string ( Y= Smile

in a file ?

DigiTan · Posted: 19 Jun 2006 05:30:04 pm Post subject:

Right now, a separate microcontroller is handling communications between the calc and the flash. The main problem until now was I pressured to conserve as much space as possible and use a serial Flash that wouldn't be fast enough to work with the calc's normal link protocol.

When I finished Calc DBS, I figured it would be better to use a faster parallel Flash and essentially make it the calc equivalent of a USB drive. Luckily, I'm not nearly as strapped for cash as last summer, so I can give it another shot. The bonus is, if it will work for TI-82, it's more than likely it can be programmed to work with all TI models.

magus57 · Member Joined: 07 May 2006 Posts: 126

So how's the progress on this? It seems very promising and something I'd be very willing to buy/make if I have the time/money.

DigiTan · Posted: 22 Dec 2006 12:24:51 am Post subject:

Oh right. This project was sort of pre-empted by Calc DBS. I actually ordered a few EEPROM chips this fall on an unrelated project. I have monday and tuesday off where I'm hoping to finish that one. If it works okay, I have a scaled-down version of it to try with the TI.

todlangweilig · Advanced Member Joined: 14 Feb 2006 Posts: 470

This seems really cool, I hope you can find the time to work on it. It would be fun to play around with.

I need to get to work on my own project, the solar powered calc :blush:

United-TI Archives -> Calculator Modifications
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