i am using the uart0 on a nrf52840 to communicate with an quectel bg95 using async api (dma) on zephyr 3.1.
from the uart interface there are connected rxd, txd, rts and cts in hardware.
when looking at those signals with the logic analyzer i can observe that the quectel modem sets its own RTS pin to low, after its initialization phase ...
... signalling to the nrf (connected to the CTS pin) that it is able to receive data.
when enabling the uart0 on the nrf (resuming from power saving mode) or at least when starting the reception from uart via the async-api i would assume that the enabled automatic hardware flow control should set its own RTS pin to low, signalling that it is able to receive data from the quectel modem (wired to quectel CTS pin).
but the RTS level of the nrf is remaining at high-level, inhibiting the quectel modem to send any data.
i tried all combinations of compile-time and run-time configurations i was able to imagine, but did not find anyone, which was working properly.
