1 files changed, 27 insertions(+), 0 deletions(-)

M module-services/service-cellular/doc/README.md

@@ 22,3 22,30 @@ It can be request of external phone number but also emergency call request,USSD 
 The logic has to recognize the request and apply proper action.
 
 ![](call_request_handling.svg)
+
+## Cellular sleep mode
+
+Conditions for cellular to enter sleep mode: 
+* no ongoing call
+* 5 seconds of inactivity in communication over UART
+
+Conditions for cellular to exit sleep mode: 
+* incoming URC
+* any activity in communication via UART to the modem
+
+Host Enables GSM Module to Enter into Power Saving Mode:
+* Pull DTR and WAKEUP pins from LOW to HIGH, and trigger the module to enter into power saving mode
+* Set AP_READY pin as invalid
+* Disable UART clock
+* CPU sentinel release block frequency request
+
+Host Enables GSM Module to Exit from Power Saving Mode:
+* Enable UART clock
+* Host pulls DTR and WAKEUP pins from HIGH to LOW, and triggers module to exit from power saving mode
+* Set AP_READY pin as valid
+
+GSM Module Enables Host to Exit from Power Saving Mode
+* Host receives the change of RI pin, then exits from power saving mode and enters into normal mode
+* CPU sentinel block frequency decreasing below 132 MHz
+* The wake-up described in the point above takes place
+