Infoportal
Unterschiede
Hier werden die Unterschiede zwischen zwei Versionen angezeigt.
| Nächste Überarbeitung | Vorhergehende Überarbeitung | ||
| embedded_systems:ethercat:choose_linux_master [2019-01-08 17:09] – angelegt mgehrig2 | embedded_systems:ethercat:choose_linux_master [2023-04-11 11:20] (aktuell) – Urs Graf | ||
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| Zeile 1: | Zeile 1: | ||
| - | ====== Choose a Linux Master | + | ====== Choose a Linux master |
| + | ===== Overview ===== | ||
| + | The linux master is a PC with Linux installed. | ||
| + | The kernel is patched with the rt preempt patch to make the system real-time capable. | ||
| + | The Ethernet port is used to connect the PC with the EtherCAT network. | ||
| + | ===== Realtime capability ===== | ||
| + | Depending on the requirements, | ||
| + | |||
| + | Very good real-time behavior (max. jitter < 30 usec) is required if: | ||
| + | * The Linux master must set the clock. E.g. if no distributed clock is used and the bus cannot be synchronized with a slave. See [[embedded_systems: | ||
| + | |||
| + | A time buffer, which is larger than the largest expected jitter, has to be used. | ||
| + | If the time buffer is too small, then in some cases the timing cannot be met and the data from this cycle is lost. | ||
| + | |||
| + | The smaller this time buffer is, the more time is available for calculations on the master. | ||
| + | However, the buffer must be large enough so that the system can reliably meet the timing deadlines. | ||
| + | A good real-time behavior enables a smaller time buffer. | ||
| + | |||
| + | The minimum cycletime, and thus the maximum frequency of the control loop, is mainly given by this time buffer plus the calculation time (EEROS). | ||
| + | |||
| + | TODO graphic time management on master | ||
| + | |||
| + | See [[software: | ||
| + | |||
| + | [[software: | ||
| + | There are also some tips on how to find a PC with good real-time performance. | ||
| Zeile 33: | Zeile 58: | ||
| Check with your contact from Acontis if this ethernet controller is suitable for one of there link layers. | Check with your contact from Acontis if this ethernet controller is suitable for one of there link layers. | ||
| - | Check chapter 2.3.1.3 of the Acontis {{: | + | Check chapter 2.3.1.3 of the Acontis {{: |
| The //" | The //" | ||