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AM3352: EtherCAT Master and Slave in the same device - simultaneously, with internal communication

Lars Heinrichs
Intellectual 460 points
Part Number: AM3352
Other Parts Discussed in Thread: SYSBIOS

Goal

We want to use a Sitara AM3352 processor is a side processor to an intel processor for realtime tasks, EtherCAT Master and IO.
Our application will be integrated into an existing project that uses EtherCAT for communication. Our system is meant to get the time from a GPS timing module and use EtherCATs Distributed Clock functionality for synchronization. 

Requirements

From what I read Beckhoff recommends using the first slave in the chain as a timing master for best accuracy (instead of the EtherCAT Master). We are fighting for every 10 ns we can squeeze out, so we want follow this recommendation.

The GPS timing module is connected to the Sitara, so we need an EtherCAT slave to run on the Sitara. However, the Sitara is also meant to be the EtherCAT Master. This means we need communication of the Master and Slave inside of the Sitara.

To make things more difficult: The EtherCAT master is meant to be run on the Sitara, but we should keep the option of running the Master Stack on the Intel, meaning we will have to use an external, high speed interface that we either loop back to another interface of the same kind on the sitara or to the intel processor. The two do not have many interfaces in common.

We want to keep the full 100 MBit/s EtherCAT speed

Questions

  1. There is a TI EtherCAT Slave stack available (correct?) and this stack is run on the PRU-ICSS and therefore does not require or exclude any operating system (correct?)
  2. The Slave stack uses Ethernet and has to be run in the PRU-ICSS section, meaning the only available interfaces are 2xMII, 1xUART, 1xeCAP, 1xMDIO (correct?)
  3. Due to 2., EtherCAT Slave can only be used with the ethernet interface (correct?)
  4. This means the EtherCAT Master, regardless of being implemented in the Sitara or the Intel, has to use Ethernet as well -> Our sytem would need 6 ethernet Phys (2x sitara as an EtherCAT master, 2x Sitara as an EtherCAT slave, 2x intel as an alternative ethercat master) (correct?)
  5. Do you see any way to get around this many Ethernet interfaces wit the given setup?

  • 0
    TI__Mastermind 35080 points

    Hi Lars, running EtherCAT master and slave on AM3352 sounds a lot, maybe possible but in any case, have you consider a bigger device? maybe something like AM572x (Dual A15 core)?

    About your questions please see below some comments

    1) PRU-ICSS EtherCAT includes PRU Firmware, drivers and patches to apply to SSC 5.12 Beckhoff stack. PRU FW is OS independent, but the rest of the software, (driver, stack, app) currently works with TI SYSBIOS.

    2) Yes, EtherCAT PRU-ICSS firmware uses PRU's Ethernet interface

    3) Yes, that is correct.

    4) No sure about your topology. But, I would say at least 1 Eth for EtherCAT master and 2x Eth for EtherCAT slave.

    5) Probably 3 is enough? assuming you are not using redundancy in EtherCAT master.. Well, in any case, AM571x you can have 2 PRU-ICSS, each one offers 2 MII ports. With additional 2 GMAC Eth ports (www.ti.com/.../am5718.pdf)

    thank you,

    Paula