As you know I tend to tinker with hardware a lot. Well I certainly have been schooled on the downside of cheap ebay parts.
I'm working on a project to make Newdos (aka TS-DOS) more tolerant of
network latency. After all, we have good solutions now possible for direct
serial over wifi, so what we need is a TS-DOS that can chat over real IP
networks.
To conduct some experiments and observe what is going on, I've made 2
RS-232 inline devices.
RS-232<----> MAX2323 <---> MAX3232 <---> RS-232
One is simply a repeater; It sits on an RS-232 link and has 2 back-to back
MAX3232 transceivers such that I can easily see the signals represented as
3V logic (compatible with my logic analyser).
RS-232<----> MAX2323 <---|-----|-> MAX3232 <---> RS-232
| |
MAX3232
| |
M100
The second device is the same repeater that also includes a connection on
one data line to an in-line M100. This allows the M100 to be a "man in the
middle" and buffer up/ delay the RS-232 characters in one direction. This
simulates wide-area network latency.
The "delay" program is attached.
Anyhow, a lot of MAX3232. Well I bought 10 of what I thought were actual
MAX3232 from ebay. Example here:
https://www.ebay.ca/itm/273089898048?hash=item3f956d2640:g:PBkAAOSw03lY42ZH
Well, my projects were being frustrated by what I thought were defective
boards.. in fact... read this -->
https://blog.heypete.com/2016/09/11/investigating-fake-max3232-ttl-to-rs-232-chips/
What a hassle. Long story short - ST3232 is a reasonably priced pin
compatible replacement for MAX3232 that you can get at digikey.
Cost me 25$ to get 10 parts, but ... I would have had several hours back in
my life had I avoided the ebay supply route.
Just goes to show you gotta be careful!
<<attachment: delay.zip>>
