Integration Manual

SARA-R4/N4 series - System Integration Manual
UBX-16029218 - R11 System description Page 39 of 157
SARA-R4/N4 series modules are designed to operate as cellular modems, i.e. as the data circuit-
terminating equipment (DCE) according to the ITU-T V.24 Recommendation [5]. A host application
processor connected to the module UART interface represents the data terminal equipment (DTE).
☞ UART signal names of the cellular modules conform to the ITU-T V.24 Recommendation [5]: e.g. TXD
line represents data transmitted by the DTE (host processor output) and received by the DCE (module
input).
☞ Hardware flow control is not supported by the “00”, “01” and SARA-R410M-02B product versions, but
the RTS input line of the module must be set low (= ON state) to communicate over UART interface
on the “00” and “01” product versions.
☞ DTR input of the module must be set low (= ON state) to have URCs presented over UART interface.
SARA-R4/N4 series modules’ UART interface is by default configured in AT command mode, if the USB
interface is not enabled as AT command / data communication interface (UART and USB cannot be
concurrently used for this purpose): the module waits for AT command instructions and interprets all the
characters received as commands to execute. All the functionalities supported by SARA-R4/N4 series
modules can be in general set and configured by AT commands:
 AT commands according to 3GPP TS 27.007 [6], 3GPP TS 27.005 [7], 3GPP TS 27.010 [8]
 u-blox AT commands (see the SARA-R4/N4 series AT Commands Manual [2])
The default baud rate is 115200 b/s, while the default frame format is 8N1 (8 data bits, No parity, 1 stop
bit: see Figure 13). Baud rates can be configured by AT command (see the SARA-R4/N4 series AT
Commands Manual [2]).
☞ Automatic baud rate detection and automatic frame format recognition are not 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 13: Description of UART 8N1 frame format (8 data bits, no parity, 1 stop bit)
1.9.1.2 UART signals behavior
At the end of the module boot sequence (see Figure 9), the module is by default in active mode, and the
UART interface is initialized and enabled as AT commands interface only if the USB interface is not enabled
as AT command / data communication interface: UART and USB cannot be concurrently used for this
purpose.