I have a use case where we must use the USB and the UART interfaces depending on our mode. I’ve found that when I set AT+QSCLK=1, the UART is disabled. I’m guessing that asserting DTR would restore the UART functionality, but we don’t currently have that wired up on our product (not connected).
Is there any other way of restoring the UART functionality without asserting DTR? It’s not a huge problem because when switching modes, we could reset the chip, but I’d prefer a less drastic measure if one exists.
Dear David_W
Your guess is correct. AT+QSCLK=1, the UART function cannot be used when the module enters sleep mode. It is indeed possible to pull down the DTR pin to wake up the module. Of course, if the module uses USB communication, it can also wake up the module so that the UART function can be restored.
In my testing, I’ve found that once AT+QSCLK=1 is set, the UART will not function again - even after setting AT+QSCLK=0 and performing communication on USB. So I believe that either DTR must be toggled or the EC25 must be reset.
We can live with resetting the EC25 in our current use case. However, it seems like this should be fixed for any possible future use cases where it is not desired to reset the device. Of course, one could also wire up DTR, but this uses an extra GPIO that may be needed for other purposes.