Can Bus items

General BVS related area
Grumpy-b
Posts: 991
Joined: Sat Dec 01, 2007 12:06 pm

Can Bus items

Postby Grumpy-b » Sun Jul 12, 2009 1:42 pm

Does anyone have any info on the Can bus sytem of controlling components. I have Vauxhaul astra mk5 (h) hydraulic power steering pump that has a "can high" and "can low" input in addition to the main power source. Before I try and get around the can bus control , does anyone know of a simple way of switching between the two states.
This control adjusts the degree of pressure created by the hydraulic power steering pump.

Regards
Grumpy-b

JonSpence
Posts: 74
Joined: Thu Jan 03, 2008 1:05 pm
Location: Rochdale

Re: Can Bus items

Postby JonSpence » Mon Jul 13, 2009 5:04 pm

Grumpy-b wrote:Before I try and get around the can bus control , does anyone know of a simple way of switching between the two states.


I do hope that someone can give you better details of this device, however I'm fairly certain that it doesn't operate how you suspect.

The CAN interface is a serial stream of data transmitted using line buffers, hence the can-hi and can-lo. A one will be when the hi input is more + than the lo while a zero will be when the low is more + than the hi. Tristate line drivers will drive the lines, but they are usually built into any development kit.

Data can be and is transmitted in both directions and to multiple devices all on the same wires. Even more confusing is the concept of PDO's and SDO's

I fear that you may be in for a steep learning curve. You will certainly need the EDS (Electronic Data Sheet) and quite a few tools to get anywhere.

Sadly that's about the limit of my knowledge. I have programed simple devices on a CAN bus but currently use a clever card to do so for me. They are also significantly less complex than power steering.


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