This limit is coming from the implementation of the NI-Serial driver being on top of the native Linux driver.
NI-Serial driver until version 21.3 leverages the 8250 driver for serial ports in Linux System. The CONFIG_SERIAL_8250_NR_UARTS parameter in the configuration kernel file defines the maximum number of serial ports handled by the kernel.To detect more than four serial ports, do the following:
3. RebootNI-Serial driver version 21.5 and newer do not rely on the 8250 driver for 843x-series hardware, and therefore can address more ports than configured in the kernel parameters.
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