SARA-R5 series - System integration manual
UBX-19041356 - R04
System description
Page 22 of 118
C1-Public
1.6.1.3
Switch-on / wake-up sequence from power-off / deep-sleep mode
shows the SARA-R5 series modules switch-on or wake-up sequence from the power-off or
deep-sleep mode:
•
The external power supply is still applied to the VCC module pins, with the module being previously
switched off (by means of the +CPWROFF AT command or by proper
PWR_ON
pin toggling), or
with the module being previously entered deep-sleep mode.
•
The
PWR_ON
pin is held low for a valid time period, representing the start-up event.
•
All the generic digital pins are tri-stated until the switch-on of their supply source (
V_INT
).
•
The baseband core and all digital pins are held in reset state; then, 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 within generic digital interfaces and USB interface due to host / device
enumeration timings.
•
If enabled, a greeting message is sent on the
RXD
pin (for more details, see SARA-R5 series AT
commands manual
).
•
The module is fully ready to operate after all interfaces are configured.
VCC
PWR_ON
RESET_N
V_INT
RXD
Module interfaces
are configured
Start-up
event
~3.6 s
0 s
Greeting text
Figure 14: SARA-R5 series switch-on / wake-up sequence description from power-off / deep-sleep mode
1.6.1.4
General considerations for the switch-on procedure
If the greeting text is not used by the external application to detect that the module is ready to reply
to AT commands, then the only way of checking it is polling: the external application can start sending
“AT” after that the
CTS
line is set to the ON state (in case UART is used as AT interface with HW flow
control enabled as default), but any AT command sent before the time when the module is ready to
reply may be not buffered and may be lost.
☞
It is highly recommended to monitor:
o
the
V_INT
pin, to sense the start of the SARA-R5 series module switch-on sequence
o
the
GPIO
pin configured to provide the module status indication or module operating mode
indication (see SARA-R5 series AT commands manual
, +UGPIOC), to sense when the
module is ready to operate
☞
No voltage driven by an external application should be applied to any generic digital interface of
the module before the initialization
of the interfaces has been finished, detectable by “greeting
text” (if enabled) or by
CTS
line going low (if HW flow control is enabled as default).
☞
The duration of the SARA-R5 series
modules’ switch
-on routine can vary depending on the
application / network settings and the concurrent module activities:
illustrate indicative typical timings only.
☞
It is highly recommended to avoid an abrupt removal of the
VCC
supply once the boot of SARA-R5
series modules has been triggered.