Ublox SARA-R410M-02B-00 System Integration Manual

SARA-R4 series - System integration manual
UBX-16029218 - R20 Design-in Page 86 of 128
C1-Public
Providing the TXD and RXD lines only
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☞ Providing the TXD and RXD lines only is not recommended if the multiplexer functionality is used
in the application: providing also at least the HW flow control (RTS and CTS lines) is recommended,
and it is in paricular necessary if the low power mode is enabled by +UPSV AT command.
If functionality of the CTS, RTS, DSR, DCD, RI and DTR lines is not required in the application, then:
• Connect the RTS input line to GND or to the CTS output line of the module, since the module
requires RTS active (low electrical level) if HW flow-control is enabled (AT&K3, default setting)
• Connect the DTR input line to GND using a 0  series resistor, because it is useful to set DTR active
if not specifically handled, in particular to have URCs presented over the UART interface (see
SARA-R4 series AT commands manual [2], &D, S0, +CNMI AT commands)
• Leave DSR, DCD and RI lines of the module floating
If RS-232 compatible signal levels are needed, the Maxim MAX13234E voltage level translator can be
used. This chip translates voltage levels from 1.8 V (module side) to the RS-232 standard.
If a 1.8 V Application Processor (DTE) is used, the circuit that should be implemented as in Figure 57.
TxD
Application Processor
(1.8V DTE)
RxD
RTS
CTS
DTR
DSR
RI
DCD
GND
SARA-R4 series
(1.8V DCE)
12
TXD
9
DTR
13
RXD
10
RTS
11
CTS
6
DSR
7
RI
8
DCD
GND
0Ω
TP
0Ω
TP
0Ω
TP
TP
Figure 57: UART interface application circuit with a 3-wire link in the DTE/DCE serial communication (1.8V DTE)
If a 3.0 V Application Processor (DTE) is used, then it is recommended to connect the 1.8 V UART
interface of the module (DCE) by means of appropriate unidirectional voltage translators using the
module V_INT output as 1.8 V supply for the voltage translators on the module side, as in Figure 58.
4
V_INT
TxD
Application Processor
(3.0V DTE)
RxD
DTR
DSR
RI
DCD
GND
SARA-R4 series
(1.8V DCE)
12
TXD
9
DTR
13
RXD
6
DSR
7
RI
8
DCD
GND
1V8
B1 A1
GND
U1
VCCBVCCA
Unidirectional
Voltage Translator
C1
C2
3V0
DIR1
DIR2 OE
VCC
B2 A2
RTS
CTS
10
RTS
11
CTS
TP
0Ω
TP
0Ω
TP
0Ω
TP
TP
Figure 58: UART interface application circuit with a partial V.24 link (3-wire) in DTE/DCE serial communication (3.0 V DTE)
Reference
Description
Part Number - Manufacturer
C1, C2
100 nF Capacitor Ceramic X7R 0402 10% 16 V
GRM155R61A104KA01 - Murata
U1
Unidirectional Voltage Translator
SN74AVC2T245
43
- Texas Instruments
Table 41: UART application circuit components with partial V.24 link (3-wire) in DTE/DCE serial communication (3.0 V DTE)
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Flow control is not supported by SARA-R410M-01B and SARA-R410M-02B-00 product versions. The RTS input must be set low to
communicate over UART on SARA-R410M-01B product version. The DTR input must be set low to have URCs presented over UART on
SARA-R410M-01B and SARA-R41xM-x2B product versions.
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Voltage translator providing partial power down feature so that the DTE 3 V supply can be also ramped up before V_INT 1.8 V supply

Ublox SARA-R410M-02B-00 Specifications

General

Brand	Ublox
Model	SARA-R410M-02B-00
Category	Control Unit
Language	English