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Design suggestion for a bus

amgalbu

Hello

I need to develop a custom board (hardware + software) to drive a set pneumatic valves. The requirements are

  • the boards can be stacked (up to 18 boards can be stacked, but I expect this number to be increased in the future)
  • the boards must be configuration-free (no dip-switches to set the board address)
  • the bus must be fault-tolerant: if a board in the stack breaks, the other boards should continue to work properly
  • pneumatic valves are "digital", so the bus must convey only on/off commands

An external board communicates with the stacked boards through the bus and drives each pneumatic valve indivudually

 

The only solution I can think of is to have two serial buses: the first one is an in-out bus used only to configure the address of each board in the stack and is used only when the system is switched on. The second bus connects all the boards in parallel, thus providing the required fault-tolerance

 

However, this solution is far from being elegant... Does somebody have a better idea?

 

Cheers

Ambrogio

Parents

  • It sounds like were at an impass here

     

    without a proper description of what solution wants to be realized, we are unable to probide any more than speculation as to what might work

     

    It is obvious that if a specefic valve has a specefic function unique to the valve then there MUST be configuration, either by the position of the controller in a pre-defined bus (Star , Linked or otherwise) or by software or by jumpers. you can NOT have a parallel system where all boards are identical and with zero configuration or knowledge of position of each control and expect it to work... sorry not going to happen

     

    the best thing right now is to provide a better description of the system operation, function and layout

  • in reply to Robert Peter Oakes

    There is no impasse here

    Each actuator must be automically aware of its position in the chain without user intervention. Configuration should happen automatically. That's why a standard bus does noto match my needs

  • in reply to amgalbu

    Each Actuator needs to know its position, this implies some kind of configuration, either through physical design or something else, If a board fails then it may not seem to be in the system (Depending on failure mode) so another board may assume its logic position if there all identical and therefor appear to the conrol system as a differnt valve to what was before the failure. this could be a big poblem

     

    you want fault tollerance such that any board failing will not stop the rest, this implies a parallel buss of some sort (Even if the data is serial), having the buss go into a board, then out to the next will break the system if the board is pulled or fails in a bad way. If the buss is parallel and un-broken if any board is pulled out for repair / replaement then there is no way for the master controller to know its position or function without some kind of local configuration, this could be through jumpers on the connector, switches on the board, programming from a aux port ont he card... something that allows the boards itentity to be known. You state all boards must be identical and auto configure with no intervention... htere has to be something that makes each position unique and known to the board. This imples configuration in some way, even if it is supplied via the connector the board is plugged into but your saying this is not acceptable

     

    These requirements are in contradiction with each other... hense... IMPASS.

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  • in reply to amgalbu

    Each Actuator needs to know its position, this implies some kind of configuration, either through physical design or something else, If a board fails then it may not seem to be in the system (Depending on failure mode) so another board may assume its logic position if there all identical and therefor appear to the conrol system as a differnt valve to what was before the failure. this could be a big poblem

     

    you want fault tollerance such that any board failing will not stop the rest, this implies a parallel buss of some sort (Even if the data is serial), having the buss go into a board, then out to the next will break the system if the board is pulled or fails in a bad way. If the buss is parallel and un-broken if any board is pulled out for repair / replaement then there is no way for the master controller to know its position or function without some kind of local configuration, this could be through jumpers on the connector, switches on the board, programming from a aux port ont he card... something that allows the boards itentity to be known. You state all boards must be identical and auto configure with no intervention... htere has to be something that makes each position unique and known to the board. This imples configuration in some way, even if it is supplied via the connector the board is plugged into but your saying this is not acceptable

     

    These requirements are in contradiction with each other... hense... IMPASS.

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