- Jan 1, 1970
Looks promising, though I'm confused as to why they give different source and sink values for the high and low sides, you'd think the two FET pairs would be the same. OTOH I guess that difference could be used to my advantage.
Best way to go on a project like this.
Yeah, I just have to convince them that even though it looks like a step backward, it'll get us forward faster, since I can build test boards that don't have the insane density and collection of hard-to-hand-assemble parts that I have to work with now.
One of the tasks at hand is to minimize this added capacitance.
Yeah, I can clearly watch the effects as I add more units to the bus:
In this case I believe the test actually involved simply turning on each driver's RE in turn to increase the number of stations listening. All 6 units were connected and powered on the line during each capture, just the RE'swere different. You can see the leading edge of the waveform becoming unacceptable pretty quickly. I think the point where packet loss became significant was about 7-8 units.
IIRC that was with the max13451.
Neutralizing that capacitance by a regenerative trick might work. If
you do that and it works hand out barf bags before you start the design
My boss suggested that without any details, implying that I could receive the signal and have units automatically loop it back. Seems to me the problem is a) there'd be too much latency between the receive and re-transmit, and b) the retransmitted signal might end up causing feedback all over the place.
Or, as I believe someone suggested, a multitone RF protocol. However,
then you need "micro-modems" at each node.
I've got a PLL-driven clock line dedicated to the interface circuit currently unused, but I could use that to drive and sync a multitone protocol if there's any way to get 1+Mbps out of it and fit it on the board.
Nah, solve it and you'll be da hero
Would be nice.
If you get too many of them clustered too close together, yes, they will
load down the line. One trick is to make the transformers wideband,
meaning that they present a very high impedance when not loaded on the
tap-off side yet reach to 5MHz or wherever you need them to go up to. On
a typical transformer the rule-of-thumb is to have the open inductive
reactance at least 4x the cable impedance at the lowest frequency to be
transmitted or received. Here you'd need a lot more.
You just started speaking alien ;-(
That's enough space for a signal transformer. If that 1cm^2 has to
contain the whole transceiver that is a tall order. Almost calls for a
custom IC design.
No, that's just the biggest single space. The board is ~1.13" round with a2x10 2mm connector on top center, the area equivalent of WS2812 'smart' LED to one side of that, and 2x 2x7 0.5mm connectors on the bottom opposite sides. The rest of the board is free for all this stuff, albeit with serious height restrictions. 3mm up and maybe 1.5mm against the parts on the bottom side board.