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Single wire CAN? #2
Description
Have you considered SWCAN? It only requires 1 wire and ground. A typical chip is MC33897 for specs.
It is extremely noise tolerant, used in new GM cars for all human interface signaling, like shifter position, buttons on steering wheel, brake and gas pedal position, door locks, nearly everything but ignition control or in EVs, the motor control.
Lower power than CAN.
Uses almost identical software to CAN. Only difference is added functions if you want to handle sleep and wake signaling.
Disadvantage is ~4 parts required for termination (2 resistors, 1 inductor, 1 cap) but no hassles with wether your on the end of the bus or not.
Activity
Mike4U commentedon Feb 6, 2018
I should of said Identical software. I've used both FlexCAN on Teensy and due_can on Arduino Due.
Just had to add a few functions.
martinjaeger commentedon Feb 7, 2018
Thanks for the remark / idea!
As far as I know, SWCAN has only quite low speed (33 kbps). In addition to that, I was afraid of more EMC issues (radiated emissions) if the communication goes partly over the power supply GND.
If you use a separate GND for the SWCAN, you can also directly use CANH and CANL. For the energy management devices we intend to use standard ethernet cables with 8 wires, so saving wires is not really necessary.
If no termination resistors are needed, this would be a major advantage, you are right. Did not know this.
What about the power consumption? Do you have values about the improvements compared to normal high speed CAN?
Mike4U commentedon Feb 11, 2018
According to the Freescale data sheet the main reasons for the SWCAN were low EMI and low power.
I can't tell from the data sheet what the average power is maybe 20mW compared to 36mW for a sn65hvd233.
This is what I did with it:
http://www.mychevysparkev.com/forum/viewtopic.php?p=14848#p14848