Hi! I'm using Quectel EC21EUX modem, connected with USB, and QMI to control it via ModemManager.
I have a question about going to sleep with a TCP connection kept so the device can wake up. I have configured the modem to go to low power mode whenever there is no traffic (AT+QSCLK=1, AT+QURCCFG="urcport","usbat", setting DTR and AP_READY pins). With this configuration, LTE modem should wake up when there is an incoming data packet. The easiest way for me put modem to sleep was to stop ModemManager. Now, if I disable ModemManager, and then try to send a network packet from backend to the device, the modem never wakes up. My guess is that when I stop ModemManager, the TCP connection is lost, and this is why modem cannot wake up as it doesn't get the message from backend. My preferred way to sleep modem is to disable USB_VBUS. On the ModemManager side, what should I do to maintain the TCP connection when putting the modem to sleep, so it can wake up when getting a message over network? Kind regards, Filip
