Thursday, March 4, 2010

VAULT-OS : Simplest Possible I2C Interface DB9?

I've traditionally been using an I2C master hub for development, now I want to build the simplest, cheapest possible I2C connection imaginable for PowerBasic DOS output. I think the best design I've been able to come up with is two resistors, two zener diodes drawing +5V off the serial port (.50 cents worth of parts). This will work on machines with standard RS-232 serial, but might not function correctly on some laptops or where the device cuts corners on the DB9 port. In the post-apocalyptic environment, I don't think the design of this circuit would be difficult to replace for anybody anywhere. A dollar buys enough replacement parts for this circuit to build fifty of them. It's not even necessary to use a soldering iron, this basic circuit could be wire-wrapped.

The great thing about the serial port is all the cheap optical isolators that are available for it. I intend to provide drivers for a parallel port I2C interface but I will make the DB9 the "de facto" standard for Vault-OS so anybody can build it in ten minutes if they need to using a serial port cable.

Anybody who can point me to the best design they have seen for I2C through DB9 RS-232 is invited to drop me a link. What I have is working but is not safe until a commercial optical isolator ($20-$30) is connected between the hardware and the I2C output. It has to be EMP proof.

There are parallel port designs with optical isolation built into the circuit but trying to make LPT the Vault-OS "standard" for I2C would be a bad idea since they are getting to be pretty rare legacy ports.

My basic stance in hardware design has been to use DB9 RS-232 as the ultimate failsafe for peripheral control and to use the parallel port (when available) only for crude relay switching circuits which could be constructed from automobile relays ripped out of abandoned cars. If Vault dwellers can't scavenge up a few car relays or a couple of diodes/resistors from the wastelands I can't help them.

This is an expression of the VOS philosophy to keep the entire core system so simple it is foolproof, decentralized, independent, asynchronous and completely maintainable indefinitely.


Hit & Run Driver said...

Tex mate where've you been... Serial DB9 are getting to be pretty rare legacy ports too.
I'm aware of this being a real issue for certain companies whose software still uses serial comms (or perhaps even Cisco techs? Whodathunkit). I was talking to a bloke who used to work for I'm pretty sure it was Toshiba, and he was telling me that they had this ridiculous situation whereby every Toshiba tech in Australia was using a HP laptop, because they still came with a serial port.
I'm glad your Vault-OS runs on legacy hardware. Are you going to have a little set-up manual on paper with a schematic for that circuit you mentioned?

Solsys said...

In all humility I must confess I have only a very slight idea of what you're talking about, but i'd just like to say : keep researching.

Build up as much experience and information as you can. There are not too many researchers into this very specific area of yours, namely EMP-proof, extremely simplistic, extremely robust.

I regard this hardware situation a bit like evolutionary theory : at some point comes a mass-extinction event that makes the simplest, most robust solutions survive. These can then thrive to build up other, complex systems.

I think you're up to to create the "extremophile bacteria" of computers. This might be a very critical component in building up a new complex society in the future, a society where access to certain technologies can be democratized. Think cuneiform writing (current technological solutions) and the alphabet (simple, robust, doesn't require a specialized cast of scribes).

In short : keep going !


Texas Arcane said...

I was thinking about it last night after I posted this and it might be good if I got out Vault-OS with the uses of the oldest legacy port described first (parallel port) and then added a driver for Serial DB-9 and then finally for USB ports. (Which I actually have a few of on every single one of my x86 devices)

I rummaged through my study and realized I not only had optical isolators for DB9 but also USB and LPT laying around, so I could post photographs showing how to buffer all three against EMP optically.