Page 9
Page 8
TYPICAL APPLICATIONS
There are many potential uses for the QS Series modules, three of which will be
described here. Figure 9 shows the QS and a MAX213 RS-232 level converter
IC from Maxim. This creates a USB-to-RS-232 converter that supports all of the
standard handshaking lines. Similarly, RS-485 or RS-422 level converter chips
could be used for designs requiring those standards.
The QS Series modules can be used with Linx RF modules to create a wireless
link between two PCs. Figure 10 shows a design using the ES Series RF
modules. An option not shown in the schematic below is that one of the output
lines of the QS module (RTS or DTR) could be connected to the PDN lines of the
RF modules, enabling the host to turn the RF modules on and off.
GND
SHDN
EN
C2+
C2-
C1+
C1-
VCC
V+
V-
16
15
0.1uF
16V
14
12
0.1uF
6.3V
0.1uF
+
13
0.1uF
6.3V
11
+
0.1uF
16V
17
24
10
25
T1IN
T1OUT
72
T2IN
T2OUT
3
6
T3OUT
T3IN
20
1
28
21
T4IN
T4OUT
R1OUT
R1IN
8
9
R2OUT
R2IN
4
5
R3IN
R3OUT
26
27
R4OUT
R4IN
23
22
R5IN
R5OUT
19
18
VCC
DSR2
DCD2
TX DATA2
RI2
DTR2
RTS2
RX DATA2
CTS2
DSR
DCD
TX DATA
RI
DTR
RTS
RX DATA
CTS
MAX213
SUSP_IND
VCC
DCD2
DSR2
RTS2
CTS2
DTR2
RI2
TX DATA2
RX DATA2
1
2
3
4
5
6
7
8
9
DB9M
USBDP
USBDM
GND
DSR
DATA_IN
DATA_OUT
RTS
CTS
DTR
TX_IND
VCC
SUSP_IND
RX_IND
485_TX
RI
DCD
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
USB Type B
Connector
GND
5V
DAT -
DAT+
GND
GND
GND
1
2
3
4
GND
SDM-USB-QS-S
VCC
220
220
DSR
DCD
TX DATA
RI
DTR
RTS
RX DATA
CTS
SUSP_IND
Figure 9: RS-232 To USB Converter
PDN
RSSI
DATA
AUDIO
AREF
NC
NC
NC
NC
NC
1
8
9
10
11
12
13
14
15
16
GND
VCC
USBDP
USBDM
GND
DSR
DATA_IN
DATA_OUT
RTS
CTS
DTR
TX_IND
VCC
SUSP_IND
RX_IND
485_TX
RI
DCD
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
5V
DAT -
DAT+
GND
GND
2
3
4
GND
SDM-USB-QS-S
RXM-XXX-ES
VCC 220
ANT
GND
LVL ADJ
PDN
/CLK
DATA
GND
LOW V DET
/CLK SEL
9
10
TXM-XXX-ES
1
2
3
4
5
6
7
8
USBDP
USBDM
GND
DSR
DATA_OUT
RTS
CTS
DTR
TX_IND
VCC
SUSP_IND
RX_IND
485_TX
RI
1
2
3
4
5
6
7
8
9
10
11
12
14
15
16
USB Type B
Connector
5V
DAT -
DAT+
GND
GND
GND
SDM-USB-QS-S
VCC
VCC 220
USB Type B
Connector
Figure 10: Wireless Modem Using ES Series RF Modules
POWER SUPPLY GUIDELINES
The USB module can be powered in two ways: from the USB bus or from an
external source. If necessary, a voltage regulator can be used to supply a clean
5V as the external source, or the VCC pin can be connected to the bus power pin
of the USB connector. Using the bus to power the module is an advantage
because the module then uses power from the host rather than from the
peripheral. This is especially helpful if the peripheral is battery-powered. Figure
8 shows the schematic for a bus-powered device.
The USB specification has strict allowances for using power from the bus. A
device is allowed to use 100mA before enumeration, 500mA during normal
operation, and 500mA in suspend mode. A descriptor stored in the EEPROM will
tell the host how much current the device will pull from the bus so that the host
can allocate the appropriate power. The modules come programmed for 100mA,
but if the final product will draw more than this, then the device descriptors will
need to be changed as described below.
CHANGING THE DEVICE DESCRIPTORS
The QS can be customized to display your product’s name, manufacturer name,
and to use different Product Identifiers (PID) and Vendor Identifiers (VID). This
allows an end user to see the final product’s name in their Windows Device
Manager and when the hardware is first loaded. The PID and VID are set by the
USB Implementers Forum and should not be changed unless the final product
has gone through the certification process and received its own unique IDs.
The Manufacturer, Description, and Serial Number strings can all be modified
using the QS EEPROM Programmer software, which can be downloaded from
the Linx web site. This easy-to-use software will reprogram the module via the
USB bus and can be done as a part of the final testing procedure.
Once the module is reprogrammed, some modifications to the driver files may be
necessary. If a VID and PID other than the default Linx numbers are used, these
numbers will need to be added to the files. This requires modifying several lines
in the .inf files and is described in detail in the QS Series Programmer’s Guide.
Modifying the name displayed by the Windows Device Manager requires
changing only one line, also described in the Programmer’s Guide.
Note: when these drivers are installed on a system with Windows XP, an error message
may be displayed stating that these drivers are not certified and could potentially crash the
system. As long as no other changes are made to the .inf files, this should not be a
concern.
USBDP
USBDM
GND
DSR
DATA_IN
DATA_OUT
RTS
CTS
DTR
TX_IND
VCC
SUSP_IND
RX_IND
485_TX
RI
DCD
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
USB Type B
Connector
GND
5V
DAT -
DAT+
GND
GND
GND
1
2
3
4
GND
SDM-USB-QS-S
Figure 8: USB Bus-Powered Schematic
TX Side
RX Side
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