Re: Fwd: CAN HW compability

Hi Daniel

Thank you for your answer

BTW by "Sensors" i mean "Parking asistance module". sorry.

Adding termination was my first response but:
1. Adding any resistor between CANH & CANL smaller than 200kohm resulted in
complete bus break down i.e. signal almost straight. as you increse the
resistance the signal is shorter and shorter until it is gone. not to
mention two 120 ohm.
2. The original entire network does not appear to have termination
resistors. The way i know that is that before i disconnected the parking
assistance module i disconnected car battery and tested resistance between
CANH & CANL and it read about 1M ohm (double checked) but as you can see in
picture 2 the signal looks very good

PS: the MCP2551 has basic (unpowered) 47kohm resistance between CANH & CANL

Best Regards
Job


2015-05-07 16:12 GMT+03:00 Daniel Perron <[email protected]>:

> Hi Job,
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>
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> The first picture really show you that you are missing the terminator
> resistor.  High rise and a very slow drop! Also you have the ringing echo
> on the high rise side.
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> You need to add a terminator. What is the value you put there?
>
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> By definition  you need terminator on both ends.
>
> Is this sensor at the end of the bus? There is a good chance it isn’t so
> you will need to add a terminator on the sensor also. (2 terminators
> needed!).
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> Daniel
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