EC21-E (quecOpen) exit from sleep if modem is off ( at+cfun=0)

Hello everybody,

In my project whcih use EC21-E (QuecOpen EC21EFAR06A05M4G_OCPU_20.001.20.001_SDK) pin 4 is used as wakeup pin which is driven by an MCU (and a transistor+resistor to provide “level shitfer” to 1.8V voltage)

So far so good…

I have noted a strange behavior if EC21 modem is turned off (i.e. AT+CFUN=0). In that case when MCU triggers the module to exit from sleep, the voltage level measured at pin4 goes to about 650mV and not to 1.8V as expected. The result is that the module doesn’t exit from sleep.
If modem is turned ON (i.e. AT+CFUN=1) everything works as expected.

Is there any hardware limitation to manage sleep exit if modem is OFF?


Hi @davdav

Please refer to section 3.3 of Quectel_EC21_Hardware_Design_V1.8.pdf (1.5 MB)


Hello @Puck-Q,
Thanks for reply.

Does it mean pin4 cannot be used as “wakeup pin” if modem is in CFUN=0 mode?

Please consider I’m using QuecOpen SDK. Is it something related to pinctrl file which could be modified?

Thanks and regards.

Hi @davdav

If the version you are using is the above phenomenon(PIN4:CFUN 1, 1.8V; CFUN 0 , 0.6V), you need to remove the pin settings in airplane mode. This part is on the modem side, so you cannot be modified base on QuecOpen SDK.


Hello @Puck-Q ,

Thank you for reply.

Do you think that the pin assignment spreadsheet can help to find a solution?

Should I modify the “mdm969607-pinctrl.dtsi” pin into kernel folder?


If yes, are you able to specify how to do that?

Thanks and regards

H @davdav

Sure,you can modify the mdm9607-pinctrl.dsti, and please refer to qcom, mdm9607-pinctrl.txt, and please note that the default functions described in this table may not exactly match the version you are using, and you can double check with the configuration from DTS.

Also what confuses me is that pin4 is always 1.8v on the default firmware with EVB board(EC21EFAR06A05M4G_OCPU_20.001) even though I send at+cfun=0

Thanks @Puck-Q,
I will check out if I’m able to modify pinctrl file even if I don’t know if I should search for gpio4 or gpio11 as per pin assignment spreadsheet.