LENA-R8 series - System integration manual
UBX-22015376 - R02
System description
Page 21 of 116
C1-Public
shows the module switch-on sequence from the not-powered mode, with following phases:
•
The external power supply is applied to the
VCC
module cellular system pins
•
The
PWR_ON
and the
RESET_N
lines immediately rise to high logic level due to internal pull-ups.
•
The
PWR_ON
input line is held low for a valid time, triggering cellular system switch-on sequence.
•
All the generic digital pins are tri-stated until the switch-on of their supply source (
V_INT
).
•
The internal reset signal is held low: the baseband core and all digital pins are held in reset state.
When the internal reset signal is released, any digital pin is set in the correct sequence from the
reset state to the default operational configured state. The duration of this phase differs between
generic digital interfaces and USB interface due to host / device enumeration timings.
•
The module cellular system is ready to operate after all interfaces are configured.
VCC
PWR_ON
RESET_N
V_INT
Internal Reset
Serial Output
Greeting Text
System State
BB Pads State
OFF
Internal Reset → Operational
Tristate / Floating Internal Reset
ON
Operational
Start of interface
configuration
Module interfaces
are configured
Start-up
event
Figure 12: LENA-R8 series switch-on sequence description
☞
The Internal Reset signal is not available on a module pin, but it is highly recommended to monitor:
o
the
V_INT
pin, to detect the start of the LENA-R8 series cellular system switch-on sequence
o
the greeting text configured on the serial interface (see AT commands manual
, +CSGT AT
command), to signal that the cellular system is ready to operate
☞
Before the switch-on of the generic digital interface supply (
V_INT
) of the module, no voltage
driven by an external application should be applied to any generic digital interface of the module.
☞
Before the LENA-R8 series cellular system is ready to operate, the host application processor
should not send any AT command over AT communication interfaces (USB, UART) of the module.
☞
The duration of the LENA-R8 series cellular system switch-on routine can largely vary depending
on the application / network settings and the current module activities.
☞
It is highly recommended to avoid an abrupt removal of the
VCC
supply during the boot sequence
of the modules
’
cellular system.
1.7.2
Cellular system power-off
LENA-R8 series modules cellular system can be gracefully switched off, with storage of the current
parameter settings in the module’s internal non
-volatile memory and a clean network detach, in one
of these ways:
•
AT+CPWROFF command (see the u-blox AT commands manual
•
Force a low pulse at the
PWR_ON
input pin, which is normally set high by an internal pull-up, for a
valid time period (see LENA-R8 series data sheet
PWR_ON
low time for graceful switch off).
☞
The graceful switch-off procedure triggered by AT+CPWROFF command or by a low pulse at the
PWR_ON
input is the recommended method to switch off LENA-R8 series cellular system.
☞
The gracefully switch-off procedure must be started as indicated above, and then a proper
VCC
supply must be held at least until the end of the cellular system internal switch-off sequence,
which occurs when the generic digital interfaces supply output (
V_INT
) is switched off.
An abrupt shutdown occurs on the cellular system, without storage of the current parameter settings
and without a clean network detach, when the
VCC
supply drops below the extended operating range.
