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Trying to find a line receiver
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viperidae:
I don't see how the bus- line gets driven. To send a logic 0 the bus+ gets pulled high and bus- gets pulled low.
They're usually driven by the driver chips through 180r resistors to +5v and 0v
spec:

--- Quote from: viperidae on January 23, 2019, 09:13:12 pm ---I don't see how the bus- line gets driven. To send a logic 0 the bus+ gets pulled high and bus- gets pulled low.
They're usually driven by the driver chips through 180r resistors to +5v and 0v

--- End quote ---
Hmm, interesting. I will remove the offending post and will re-post a schematic for just the IEBUS receiver, which was the original requirement.
spec:
UPDATE #1 2019_01_24 (R5 value corrected)

Attached is the IEBUS receiver only:

https://datasheets.maximintegrated.com/en/ds/MAX9140-MAX9144.pdf

https://www.diodes.com/assets/Datasheets/ds30312.pdf
T3sl4co1l:
Why not use this much simpler circuit?

https://www.onsemi.com/pub/Collateral/FIN1028-D.PDF

(It's just a receiver. I'm not going to draw that up. :P )

LVDS receivers are normally spec'd for 100mV, but typical performance is a comparator with <10mV offset.  Or, just use a comparator; or best yet, a comparator with adjustable offset, if you can find one (or use an op-amp that does, that is also fast enough to be usable as a comparator at this clock rate?).

Unfortunately, adding an offset to a bus is surprisingly difficult -- the above example works for one-offs, but it's not scalable because it puts a current offset into the bus itself.  A source and sink around the offset resistor would fix that in the average case, but would leave a worst-case residual offset.

The other difficulty is EMC.  The previously stated 5V common mode range is ridiculous for an automotive environment (perhaps why this bus didn't last long?).  Heavy common mode filtering at least will be necessary.  Exceeding the CM range activates ESD clamp diodes, stomping out bits.  An isolated receiver might be okay (has to be done carefully to avoid loading the bus with capacitance), but this is a somewhat heroic level of effort and maybe it's not necessary, I don't know.

Or maybe a completely different tack is acceptable -- have I read this correctly, that it's a high clock frequency ("6MHz") modulated at a much lower symbol rate?  Just AC-couple it, read it out from a transformer!  Eliminates the oddball offset, eliminates common mode and isolation problems, lets you do whatever you need locally to process the signal, and commodity transformers may be suitable (think Ethernet 10/100, or ISDN transformers if you can still find 'em).  Downside, this puts a fair amount of impedance on the bus, so again, it's not scalable.

Tim
viperidae:
IEBus is a multi-master bus like CAN, so there is arbitration to deal with too.
My understanding with all these LVDS/RS485/etc receivers is they won't switch the output state until the differential input goes negative. That never happens in IEBus, it's either driven positive or left to go back to zero, like CAN. CAN receivers aren't suitable as they require about 10x higher voltage swings.

The common mode doesn't get that high and the bus is supposed to usually sit at around 2.5V. I think the driver chips bias the bus to half their 5V supply rail.

It's not that uncommon as an automotive bus. It's designed for Infotainment systems. Pioneer used it, Toyota used it, Honda used it.
It's how the navigation systems, aux inputs, cd changers, head units, satellite radio options, etc, all talk to each other.

It spanned a few generations of models in Honda cars (Civic's, Accords, Odyssey's), so probably late 90's to mid 00's. Toyota Prius's and Corolla's used it too. I guess they've moved on to different standards now. I don't know why they didn't use a low speed CAN bus. My Honda has a high speed CAN for the engine/transmission/etc and a single-wire CAN for the body network. I don't know why they wouldn't use the body CAN network. The HVAC already uses that to control the AC compressor relay. The navigation system connects to the high speed CAN to read the trip computer data from the ECU and the gear selection to activate the rear view camera. The gauge cluster connects the two CAN networks and passes some message types between the two.
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