LENA-R8 series - System integration manual
UBX-22015376 - R02
System description
Page 26 of 116
C1-Public
1.10.1
Cellular UART interfaces
1.10.1.1
Cellular main UART interface
LENA-R8 series cellular system includes a main primary UART serial interface for communication with
an application host processor, supporting:
•
AT / data communication
•
Multiplexer protocol functionality (see
•
FW upgrades by means of the FOAT feature
The UART interface provides RS-232 functionality conforming to ITU-T V.24 recommendation
with CMOS compatible signal levels: 0 V for low data bit or ON state, and 1.8 V for high data bit or OFF
state (for detailed electrical characteristics, see the LENA-R8 series data sheet
), providing:
•
data lines (
RXD
as output,
TXD
as input),
•
hardware flow control lines (
CTS
as output,
RTS
as input),
•
modem status and control lines (
DTR
as input,
DSR
as output,
DCD
as output,
RI
as output)
3
.
The module is designed to operate as cellular modem, as data circuit-terminating equipment (DCE)
according to the ITU-T V.24 recommendation
. A host application processor connected to the
module through the UART interface represents the data terminal equipment (DTE).
☞
UART signal names of the modules conform to the ITU-T V.24
: e.g.,
TXD
line represents data
transmitted by the DTE (host processor output) and received by the DCE (module input).
The UART interface is configured by default in AT command mode: the module waits for AT command
instructions and interprets all the characters received as commands to execute.
All supported functionalities can be configured by the AT commands documented in the AT
commands manual
Hardware flow control is enabled by default, and it can be enabled/disabled by AT commands (see the
AT commands manual
, &K, +IFC AT commands).
One-shot autobauding is supported and is enabled by default: automatic baud rate detection is
performed only once, at module start up. When autobauding is enabled, the first AT command sent
to the module is not processed, because it is used by the module to detect the baud rate. After the
detection, the module works at the detected baud rate which can only be changed via the +IPR AT
command. For more details, see the AT commands manual
115
’
200 bit/s, 230
’
400 bit/s, 460
’
800 bit/s, 921
’
600 bit/s baud rates are supported.
The 8N1 (8 data bits, no parity, 1 stop bit) frame format configuration is enabled by default (illustrated
in
), and other frame formats can be set by appropriate AT command (see the AT commands
, +ICF AT command). The 8N1, 8N2 and 8E1 frame formats are supported.
D0
D1
D2
D3
D4
D5
D6
D7
Start of 1-Byte
transfer
Start Bit
(Always 0)
Possible Start of
next transfer
Stop Bit
(Always 1)
t
bit
= 1/(Baudrate)
Normal Transfer, 8N1
Figure 16: Description of the UART 8N1 frame format (8 data bits, no parity, 1 stop bit)
3
Alternatively, the
DTR
,
DSR
,
DCD
and
RI
pins can be mutually exclusively configured as auxiliary secondary UART interface.
Note that the
DSR
and
DCD
pins toggle as output for ~600 ms during the boot of the module. The
DSR
and
DCD
pins are also
set as output during the FW update over USB interface.
