Design Guidelines; Power-Up Sequence; Module Switch-Off; Sleep Mode Management - Sierra Wireless AirPrime HL77 Series Product Technical Specification

5. Design Guidelines

5.1.

Power-Up Sequence

Apply voltage to the VBATT pin for at least 10 ms (TBC) prior to applying a low-level logic to the
PWR_ON_N pin.
Apply a low-level logic to the PWR_ON_N pin (pin 59); within approximately 25ms, VGPIO will appear
to be at 1.8V. Either UART1 or the USB interface could be used to send AT commands. The AT
command interface is available in about 25 seconds (TBC) after PWR_ON_N for either UART or USB.
When using UART, the AT command interface is available after the transition of UART1_CTS from
high to low level.
When using a USB connection, the AirPrime HL77xx module will start communicating with the host
after USB enumeration. The time when AT commands can be sent will depend on the initialization
time on the USB host.
Note: As PWR_ON_N is internally pulled up with 1MΩ, an open collector or open drain transistor must be
used for ignition.
5.2.

Module Switch-Off

AT commands AT+CPOF and AT+CPWROFF enables the user to properly switch the AirPrime HL77xx
module off.
5.3.

Sleep Mode Management

AT command AT+KSLEEP enables sleep mode configuration; this command can only be used with
serial link UART1.
AT+KSLEEP=0:
The module is active when the DTR signal is active (low electrical level).
•
When DTR is deactivated (high electrical level), the module enters sleep mode after a while.
•
On DTR activation (low electrical level), the module wakes up.
•
AT+KSLEEP=1:
The module determines when it enters sleep mode (when no more tasks are running).
•
Any character on the serial link wakes the module up. The first character is lost.
•
The module never enters sleep mode.
AT+KSLEEP=2:
Note: The DTR signal must only be set to low-level "0" to wake up from Sleep mode. This pin must be set
to high-level "1" (1.8V) or left floating (internal pull-up) for all other modes.
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