I have an half-duplex RS485 bus with 10-20 different nodes. Some of them are 8-bit MCU based, one of them could be Linux embedded.
It's half-duplex, so it's important for the transmitter node to disable the driver as soon as the last transmitted bit is shifted out.
Many small low-cost MCU has interrupt on transmission complete, so the delay of disabling the driver is usually on the order of microseconds.
Some new Cortex-M MCUs have an automatic control of external RS485 transceiver, so the delay is really zero.
What happens in Linux embedded systems? Many of them are based on NXP i.MX CPUs and it seems they aren't able to control the RS485 direction in hardware, but some code is needed. This approach could increase the delay of disabling the driver in the order of milliseconds.
Is it possible that a powerful CPU isn't able to control RS485 driver in hardware?