September-8th-2020, 04:17 PM
(September-8th-2020, 03:14 PM)Armin@netPI Wrote: The communciation interface beetween a netX chip and the Host chip is SPI. Next to the 4 standard SPI signal a 5th signal is needed which is the chip select signal.On a basic understanding, we can conect more than one spi device to raspberry pi: Raspberry pi 4 with more spi devices
For example with netHAT module the pin 24 is used and hardwired to operate as chip select. If you now would operate two netHATs the same both modules would use pin 24 as chip select and hence both modules would get addressed by the Raspberry Pi CPU the same time which causes a conflict. What you would need are multiple netHAT modules that differ in the pinout and would user other free pins for the chip select. So there is no possibility since such modules no not exist. Or you build your own modules ...
The driver indeed has a parameter which SPI interface to use. You specify the Linux "/dev/spidevx.x." in a configuration file like "/dev/spidev0.1" or "/dev/spidev0.2" or "/dev/spidev0.3" etc. Today the driver just looks a single time to the single configuration file. There is no feature to get multiple driver instances running.
but the driver cannot handle more than one devices?
With a Nucleo Board and a netShield, it is better possible to use more than one device?
Or could the driver be changed to support more than one device?
(September-8th-2020, 03:14 PM)Armin@netPI Wrote: What exactly do you mean with CrossLink time? Do you mean the time to exchange POWERLINK data located the netX buffers with an application running on Linux? A customer measures the SPI overall performance and came to the result that it costs you 300us to 1.5ms until you have exchange the IO buffers from netX with a Linux application.
Yes, thats the right interpretation. I understand, in worst case, the exchange time could be about 1.5ms or perhaps more? And I think: if the application is a little bit more complex, about copying more data, it could be longer?
There is no garantied maximum (small) time, because the basic linux is not realtime?
With a Nucleo Board and a netShield, it is better possible to realize a fast "gateway" ?
Stefan
