On 1/12/24 11:31, steves via groups.io wrote:
If you are trying to drive I2C over long distances, consider using a PCA9600 on each end of the run.? It is a lot harder to blow up than some other buffer chips (e.g. PCA9617).? You can also use higher signal voltage levels (e.g. 12V), but it is tolerant to those higher voltages even when using low-voltage signaling.
Interesting Steve, although it is now way past being even historical, but when did this higher voltage version become available? My unpleasant run-in with it was in the latter half of the 90's and was my first and last, as I forbid the purchase of anything using it. The first USB had much the same problems, with a 5' limit to the length of cable. That quickly led to the use of hub chips in both ends of the cable. Cheap, had enough power to drive terminations if the cabling was good enough. Attention to the terminations soon made 10 meter cables possible, just bring the shekels for quality cabling.
It seems every new class of interface designers have to learn about the real world limits their prof didn't teach them about, often at the expense of their parent companies commercial failure. Some learned, and some are flipping burgers at in&out today.
Its amazing what can be done with a properly terminated transmission line. I was a bench tech at Oceanographic Engineering in 1959 and suddenly found myself in the middle of a project to put TV cameras on the Trieste in prep for its one and only dive into the Marianas trench northwest of the philipines. We were building what was then the smallest TV camera, to be towed thru sewers to inspect for storm water ingress. that was before the first video tape recorder so due to the size of to gondola on the Trieste we were limited to bringing in the video, and displaying it on 5" b&w monitors which were recorded ether with a Leica camera, but 35mm film spools were bulky so most of the pix you saw later were shot with a minox camera. But the Trieste gondola only had 6, 16 gauge std Packard automotive wires thru its wall, so we had to get video for 2 cameras, and lights, and 2 pan & tilt things. Thru those 6 wires. So the first thing we did was get a 1000 gallon stock watering tank, threw in 300 lbs of salt and pumped it full of mission bays brackish water since we had a fishing dock in the back yard to simulate the pacific ocean. Then went to NAPA and bought a 100' roll of that wire and unrolled it in the tank. Setup sweepers to scan that wire to 10 MHz. As long as the test gear was grounded to the tank it looked usable. we redesigned the video for a 40 ohm cable and it worked. The rest is old old history now. As a bench tech, I was a fly on the wall but I was there. The external pressure against the wall of that gondola with Lt. Walsh and Jacques Cousteau in it at the bottom of the trench? 18,000 psi. Those guys in the carbon fiber tube diving on the Titanic, signed their own death warrant, they never felt a thing because the collapse only took a millisecond.
Solve problems is what real engineers do and I was blessed by having the opportunity to learn from them.
Cheers, Gene Heskett.
--
"There are four boxes to be used in defense of liberty:
soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author, 1940)
If we desire respect for the law, we must first make the law respectable.
- Louis D. Brandeis
Gene Heskett