The Industrial Raspberry Pi Forum

1. Using a RevPi Connect with Codesys license as Profinet device. No Profinet IRT Gateway.
   
   • merits: no Gateway needed, no need to transfer data (process image) between RevPi and Gateway (would it be faster/have less latency?).
   • demerits: Codesys license needed. Codesys does not seem to support Conformance Class C/IRT features.
   • unclear: What latency can I expect when the RevPi Codesys Profinet device receives a message from a Profinet controller and responds to it? As far as I know, Codesys is not providing IRT/conformance class C, but for option 2, the IRT part is still unclear to me.
2. Using a RevPi (e.g. Core S) with the Profinet IRT Gateway.
   
   • The RevPi copies the process image every ~5 ms. So while according to the data sheet, the Gateway supports Profinet IRT, I am really not sure where this IRT feature is beneficial . Does IRT mean that the Gateway and some (IRT capable) Profinet controller can exchange data quickly (and with a jitter <31.25 µs)? But what does that mean exactly and what is it useful for if I cannot access this data quickly enough? Through the RevPi, I can only read or write data to the Profinet with at least 5 ms delay (because of the process image update), right? So what is the benefit of using the IRT Gateway? In what kind of setup does the IRT part make a difference having a RevPi attached to the Gateway?

unclear: What latency can I expect when the RevPi Codesys Profinet device receives a message from a Profinet controller and responds to it? As far as I know, Codesys is not providing IRT/conformance class C, but for option 2, the IRT part is still unclear to me.

The RevPi copies the process image every ~5 ms. So while according to the data sheet, the Gateway supports Profinet IRT, I am really not sure where this IRT feature is beneficial . Does IRT mean that the Gateway and some (IRT capable) Profinet controller can exchange data quickly (and with a jitter <31.25 µs)? But what does that mean exactly and what is it useful for if I cannot access this data quickly enough? Through the RevPi, I can only read or write data to the Profinet with at least 5 ms delay (because of the process image update), right? So what is the benefit of using the IRT Gateway? In what kind of setup does the IRT part make a difference having a RevPi attached to the Gateway?

demerits: Codesys license needed. Codesys does not seem to support Conformance Class C/IRT features.

So what is the benefit of using the IRT Gateway? In what kind of setup does the IRT part make a difference, having a RevPi attached to the Gateway?

1. What is the minimum latency which can be achieved when the RevPi with Profinet IRT gateway receives an Input (say a single Byte) and mirrors this Byte to the Output?
2. When is the IRT property of the Profinet IRT gateway useful? Is the IRT property required by some Profinet IO controllers? My current guess is that the communication between Profinet IO controller and the Profinet IRT gateway will be fast (and with very small jitter) but the data will still be accessible only after several milliseconds due to the delayed communication between Profinet IRT gateway and the RevPi itself?

• RevPi Profinet IRT Gateway receives profinet message
• RevPi gets Input from IRT Gateway
• RevPi mirrors Input to Output (will the use of mainloop() or cycleloop() be the better choice in terms of latency?)
• RevPi Profinet IRT Gateway receives the Output and sends out a Profinet message