Homebrew SX Programmer

awasson

Well, after a 15 year hiatus I'm back into the smell of solder, little bits of insulation on the floor and small wheeled devices bumping around and falling off my desk. I'll thank February 2004 Nuts & Volts and John Williams for that (One of these days I will buy a BS1 and a Pololu controller and build the worlds smallest basic bot)

Anyway after reading the December 2004 Nuts & Volts article about the SX chips I dropped by EBay and picked up a reconditioned SX Tech Programming board from the Parallax EBay shop. It'll be here within a few days but I don't think it comes with an SX-Key or an SX-Blitz.

Does anyone know of schematics or other info on how to build one? The other alternative is to just order one from the Parallax site but, I've always built things from scratch so I'd like to try my hand at it first.

Thanks,
Andrew

Paul Baker

All the information you need to program an SX is here: http://www.parallax.com/dl/docs/prod/sx/DeviceProgramming.pdf

But of course you need a device to drive the signals properly, likely requiring you to program another chip, quickly getting you into the chicken and the egg situation.

Additionally this provides no means for in system debugging which the SX-Key provides, though within the last month hidden instructions for the SX have been disclosed within this forum which would allow you to write your own debugger. But why re-invent the wheel? The SX-Key is a very cost effective development tool, plus you get the support of Parallax should something go amiss.

This is by no means a beginners project, and because of the SX-Key's popularity and affordability, there hasn't been much desire or impetus to develop a competing programming platform.

Paul

awasson

Hi Paul,
Thanks for the info and yes in system debugging was something that caught my eye when I started reading about the SX-Key. I figured that since SX chips had been around for a while before Parallax picked them up, there might be some interesting reference material around about homebuilt programmers.

I want to play with some ideas for co-processor boards for my Boe-Bot and maybe come up with some main brain units for other bots I'm thinking about building.

I think for it's cost, the SX-Key is a lot of bang for the buck so I'll probably order one and start playing right away. I'd still like to give building one from scratch a try when I have a chance and am more familliar with SX technology. I've been out of the loop for a while but I was part of a team that designed and built custom boards for 8080/85 and 1802 chips in my senior high school days.

Anyone remember 1802's? They rocked in their day!

Anyway, thanks for the info Paul.

Andrew

Paul Baker

I would wait before you receive your ebay purchase, while your probably correct that it doesn't include an SX-Key, you don't want to have a Homer moment (doh!) if you are wrong. Or you could email the seller to verify.

Paul

With your experience with older processors, you'd probably enjoy this thread in the Sandbox forum: http://forums.parallax.com/showthread.php?p=464494

Post Edited (Paul Baker) : 1/14/2005 11:17:40 PM GMT

Ken Gracey

Andrew,

If your time is of any consequence then your best bet is to simply buy one. We spent well over a couple of years developing this tool (it is the one and only well-known SX programming tool at this point). Considering the cost (you can buy the SX-Key alone for less than $100) the value of your time would work out to about 10 cents per hour by the time you were done designing your own and it would be without any debug capabilities.

Worst yet, we have not published a schematic of the SX-Key. We could, but it's not a priority at the moment. The tool used to cost over $300, by the way.

Best of luck!

Ken

Forrest

Here's the instructions to build your own Fluffy2 - a free SX programmer http://www.semis.demon.co.uk/Sx/SXmain.htm
Note you'll need to program a Microchip PIC16F84 to get Fluffy2 to work - so this is only a good idea if you already have a PIC programmer. Some PIC programmers are very inexpensive - I recently built the P16Pro (also known as Kit 96) - available here for $11.95 http://www.alltronics.com/kits3.htm

SteveW

For what it's worth, I designed a super-simple Fluffy2-derived SX programmer a while back, but never needed to build it, so it's untested.
It generates the programming voltage by scrounging an extra voltage doubler stage from the MAX232, so it can run from the 5V available on the programming connector on the target - it's untested, but should work (and it simulates OK). It's a single-sided 54x32mm PCB, with pinmount parts in through-hole, and surface mount parts on the back, so should be mechanically robust, but as cheap as possible to etch.
If anyone wants to build it (or derive from it), go for it. No guarantees it works, and it (obviously) doesn't offer the excellent debug facilities of the SX-key.
I hope it's useful to someone - it's doing no good sitting here.

Steve

SteveW

By the way - that SX_Prog design really isn't production grade. It pushes the Max232 out of spec, at the very least, and it's possible that the programming voltage needs development - basically, it needs finishing, before it's suitable for newbies to use, and I just don't have the tmie (or need)

Steve

awasson

Awsome, thanks for all of the replies and direction.

Paul, I'll definitely take your advice and hold off until I get the SX Tech Board and that Sandbox thread is great! I only got through the first 2 pages but I'll be back. I remember all of the H/W but most of it was way beyond the reach of my "pocket money" budget. My first real computer was a Neutronics Cosmac Elf and I struggled with assembler. It got lost somewhere along the way but I have some of the old chips and might build another just for prosperity.

Ken, Point taken. The SX-Key is pretty slick and easily the best way to access the SX Technology!

Forest and Steve, I remember finding some info on the Fluffy programmer but it wasn't as well documented as the links you supplied. I think I will give it a try just for fun. (my wife's going to love this... not)

Thanks again,
Andrew