SARA-G450 - System integration manual
UBX-18046432 - R08
Design-in
Page 94 of 143
C1-Public
Providing the TXD, RXD, RTS and CTS lines only
If the functionality of the DTR, DSR, DCD and RI lines is not required, or the lines are not available:
Connect the module DTR input line to GND.
Leave the DSR, DCD and RI output lines of the module unconnected and floating
If RS-232 compatible signal levels are needed, the Maxim 13234E voltage level translator can be used.
This chip translates voltage levels from 1.8 V / 3.0 V (module side) to the RS-232 standard.
If a 1.8 V application processor (DTE) is used and module (DCE) generic digital interfaces are
configured to operate at 1.8 V (V_INT = 1.8 V, if VSEL pin is connected to GND; see
), the circuit
should be implemented as described in
TxD
Application Processor
(1.8V DTE)
RxD
RTS
CTS
DTR
DSR
RI
DCD
GND
SARA-G450
(1.8V DCE)
12
TXD
9
DTR
13
RXD
10
RTS
11
CTS
6
DSR
7
RI
8
DCD
GND
0
Ω
TP
0
Ω
TP
0
Ω
TP
0
Ω
TP
21
VSEL
Figure 53: UART application circuit with partial V.24 link (5-wire) in the DTE/DCE serial interface (1.8 V DTE / 1.8 V DCE)
If a 3.0 V application processor (DTE) is used and module (DCE) generic digital interfaces are
configured to operate at 3.0 V (V_INT = 3 V, if VSEL pin is left unconnected; see
), the circuit
should be implemented as described in
TxD
Application Processor
(3.0V DTE)
RxD
RTS
CTS
DTR
DSR
RI
DCD
GND
SARA-G450
(3.0V DCE)
12
TXD
9
DTR
13
RXD
10
RTS
11
CTS
6
DSR
7
RI
8
DCD
GND
0
Ω
TP
0
Ω
TP
0
Ω
TP
0
Ω
TP
21
VSEL
Figure 54: UART application circuit with partial V.24 link (5-wire) in the DTE/DCE serial interface (3.0 V DTE / 3.0 V DCE)
If a 3.0 V application processor (DTE) is used and module (DCE) generic digital interfaces are
configured to operate at 1.8 V (V_INT = 1.8 V, if VSEL pin is connected to GND; see
), 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 the 1.8 V supply for the voltage
translators on the module side, as described in