26
26
Pinout and I/O Description
26
PMIC_ON_REQ
O
3V3_LVTTL
Typically connected to the control pin of an external power switch.
The power switch is expected to enable VDD_3V3 when
PMIC_ON_REQ is high, and to disable VDD_3V3 when it is low.
MODULE_RDY
O
3V3_LVTTL
Level is high when module is operating, and low when in standby
or reset.
Level becomes high about 300
milliseconds after powering up,
unresetting, or waking up after
standby
The external power switch is optional. When not using an external power switch, always
connect VDD_BAT together with VDD_3V3.
An example optional circuit with an external power switch and an on/off push-button is
shown below.
The module can be put in standby by either:
•
Entering the
exePowerMode, standby
user command;
•
Driving the ONOFF pin low for at least 50ms (i.e. pressing the button for at least
50ms).
After standby is requested, the module terminates all running processes, unmounts the
external SD card (if applicable) to avoid any log file corruption, and drives the
PMIC_ON_REQ pin low to turn off the main power supply (VDD_3V3). The module power
consumption in standby is <5mW. The current state of the module (standby or active) can
be monitored with the MODULE_RDY pin. MODULE_RDY is low during standby.
When in standby, driving the ONOFF pin low for at least 50ms wakes up the module. The
module drives the PMIC_ON_REQ high, and restarts in the configuration stored in the boot
configuration file.
The ONOFF pin is internally pulled up and has a built-in debouncing circuit.
Do not drive a non-
zero voltage into input pins (pins type “I” in the tables in chapter 3)
when the module is in standby, i.e. when the VDD_3V3 supply is turned off.
