Hacker News Reader

Comment by throwup238 | Hacker News Reader

My free square is one of their control computers’ parallel ports frying out and now they’re unable to find a replacement because they buy them all as old stock off of ebay [1].

The ports are used as hard realtime GPIO so if some of the electrical isolation failed downstream, it could take out the motherboard. Back before Vista’s security model change, drivers could fill DMA buffers to the parallel ports controller and get hard realtime time outputs on Windows so there’s a quite lot of old industrial control systems running on a thread.

[1] https://www.mercurynews.com/2022/09/17/how-clever-mechanics-...

View on HN

Wow that takes me back. My graduate physics experiment ran on two MS-DOS computers with Turbo Pascal programs exercising the parallel ports. Each machine had a grotesque board that I made, with multiple ADC and DAC channels. I finished in 1993. By that time, of course, everything was obsolete, but I wasn't going to delay my project by upgrading.

Obsolete is good! Hobbyists running mini CNCs and converting old manual Bridgeports exploited the obsoleteness well into the 2010s by buying up really cheap old machines to run Windows XP with MachCNC, which could drive the CNC via parallel port (with a proper expansion board, which used to be the expensive part).

It wasn't until the microcontrollers got powerful enough and Stratasys FDM patents expired that open source Klipper/Marlin firmware from the 3d printer community replaced MachCNC.

Indeed, PC interfacing was what got me into microcontrollers. I had already mastered microprocessor interfacing and coding, but on desktop machines. Our lab got a Mac, and the only reasonable interface port was serial. So it made sense to put a MCU on the other end of that serial port, to continue my explorations. I still had to program the MCU with my MS-DOS machine, using a device programmer that I hacked together -- using the parallel port, and a freeware 8051 assembler.

Today, that MCU is a Teensy.

> My free square is one of their control computers’ parallel ports frying out and now they’re unable to find a replacement because they buy them all as old stock off of ebay

The last time I experienced a BART shutdown, the cause was that someone had found a box in one of the stations somewhere, and they (1) assumed it was a bomb; and (2) shut down the entire system. I'm not sure what stopping the trains while you investigate the bomb you've found accomplishes, but I don't think there were efforts to find additional bombs. (The box was not actually a bomb.)

Forgive my arrogance, but nothing presented in that article should be such a big blocker. Spare parts for the traction gear sure, but none of the computing "problems" make any sense.

It's not like hard real time systems aren't available. More concretely, they talk about running a DOS virtual machine on a laptop to download logs from the cars, but there's no way that protocol is so complicated it couldn't be re-implemented reasonably.

This sounds more like "It's cheaper to just buy old stuff off ebay than it is to actually care about this system"

I'd wager it is technically a "cheaper" problem, but I'd also consider the axis that this is public transit, an industry known for being neglected budget-wise. Reverse engineering/reimplementation with competent parties may be laughably out of budget.

It's neglected because public transport is usually subsidized in almost every country. It's just not directly profitable, like roads.

US is in general very reluctant to invest into profitless projects.

No, but like roads, public transit leads to greater economic activity and boosts GDP. Good public transit also increases social and financial mobility, makes other clean air targets easier to hit, and decreases medical costs [0] while increasing the number of financially-productive hours a citizen can work - because a healthier citizen is a more economically productive one.

America seems utterly incapable of grasping many second-order effects. For another example, look to the ROI of investing in the (coninuously underfunded) IRS [1]

[0] https://pmc.ncbi.nlm.nih.gov/articles/PMC4917017/

[1] https://www.businessinsider.com/irs-tax-audits-recover-12-do...

Yes, thanks for elaborating. I seem to be not clear in my point: that public transit is subsidized and it's a good thing, we should not expect to see an immediate profit from it, and should not expect a commercial company willing to invest into it.

I appreciate the clarification, my mistake taking your original comment the wrong way. I'm a little reassured too - what seems to be an Americanism (things that don't turn a profit aren't worth doing) feels like it's seeping into my locale as well, so I may be overly sensitive to it. It's nice to be told I was wrong in this instance.

It sounds even more like decades of low budgets.

Would be surprised if they didn't have optoisolators to cater for that scenario

Apparently they've never heard of a PLC or even digital IO pci card

Reply on news.ycombinator.com