Electronics > Beginners
Trying to find a line receiver
viperidae:
I'm been trying to find a robust, simple solution to reading a data line.
The line is the IEBus standard, a differential line with > +120mV a logic 0 and < +20mV logic 1. Common mode is around 2.5V, 120R terminated at each end of the bus.
The line speed is on the order of 20kbps. I'd need to be able to detect the difference between 8us and 20us pulses.
There are Renesas/NEC chips around with built in IEBus peripherals but they not easy to come by.
There are also circuits on the web using a comparator, with a resistor to pull the positive bus line down a bit, so the +20mV is pulled below 0.
Unfortunately the levels are too low to use a CAN bus transceiver. I don't really know what to look for in a differential line receiver that is suitable.
Edit:
Examples of hard to find/obsolete parts:
Line receivers:
R2A11210
HA12187
Controllers with built-in receivers:
D74042
UPD6708
As background, I'm trying to replace the Japanese navigation system in my old 2005 Honda Accord with a Raspberry Pi running Crankshaft-ng to give me Android Auto.
I need to interface with the HVAC and existing audio system, as the old navi provided the only interface for complete control. This is over Honda's GA-NET II bus, an implementation of NEC/Renesas IEBus. Toyota use it as well and call it AVC-LAN.
Thanks in advance.
spec:
Hi viperidae
Just connect the two data lines to the + and - inputs respectively of a high speed comparator, like the AD8468, running from a 5v supply line, and the output from the comparator will be the line signal at TTL/CMOS levels.
https://www.analog.com/media/en/technical-documentation/data-sheets/ad8468.pdf
viperidae:
I believe the problem is the BUS+ line is always higher than BUS-
It's a matter of how much higher.
A logic 0 is when a device on the bus drives the line and a logic 1 is when the line is left to return to zero via the 120R termination resistors.
spec:
--- Quote from: viperidae on January 22, 2019, 12:48:46 am ---I believe the problem is the BUS+ line is always higher than BUS-
It's a matter of how much higher.
A logic 0 is when a device on the bus drives the line and a logic 1 is when the line is left to return to zero via the 120R termination resistors.
--- End quote ---
Apologies- that's what happens when you reply in a rush. :-[
Just some links which may be of use on this thread:
https://en.wikipedia.org/wiki/IEBus
http://www.datasheetcatalog.com/datasheets_pdf/U/P/D/6/UPD6708.shtml
http://pdf1.alldatasheet.com/datasheet-pdf/view/248923/RENESAS/HA12187FP.html
NEC uPD6708 IEBUS Protocol Control LSI Chip: http://pdf1.alldatasheet.com/datasheet-pdf/view/63444/HITACHI/HA12187.html
NEC uPD78098 Microcontroller with IEBUS Interface: https://www.datasheetarchive.com/pdf/download.php?id=4815a2c428ade8f21639b96e3c06694be3218b&type=M&term=uPD78098B
spec:
+ viperidae,
I have done a design for an IEBUS line reader (IEBLR) and hope to draw it up and post within the next few hours. But, in the mean time, can I ask a few questions?
How would you like the IEBLR to be powered: battery, mains, or from the unit reading the data line from the IEBLR.
How many IEBUS lines would you like to read simultaneously at any one time?
Are you OK with building a simple circuit?
Navigation
[0] Message Index
[#] Next page
Go to full version