INTERFACE MODULE
QS SERIES
WIRELESS MADE SIMPLE
®
SDM-USB-QS-S USB MODULE DATA GUIDE
DESCRIPTION
The Linx QS Series USB module allows the
0.812"
rapid addition of USB to virtually any device.
Housed in a compact SMD package, the QS
module provides a complete solution for
converting between USB and CMOS / TTL logic
0.630"
USB MODULE
level serial sources. The module can be directly
SDM-USB-QS-S
connected to virtually any serial device
LOT 10000
including microprocessors, RS-232 / RS-485
level converters, or Linx wireless RF modules.
The QS module is completely self contained, so
it requires no external components, (except a
0.125"
USB jack) and includes all necessary firmware
and drivers, freeing the designer from
complicated programming. Power can be
Figure 1: Package Dimensions
supplied externally or from the USB bus. Both
USB 1.1 and USB 2.0 are supported at data rates up to 3Mbps.
FEATURES
Single chip USB-to-asynchronous
serial data conversion
Low cost
3Mbps baud rate
Supports low-speed USB
Full handshaking support for RS-232
and RS-485
Bus- or self-powered
VID, PID, serial number, and
descriptors programmed via USB
No external components needed
(except a USB jack)
Compact surface-mount package
Drivers and firmware included
Supports Windows 98/2000/ME/XP
USB 1.1 and 2.0 compatible
APPLICATIONS INCLUDE
Interface / Upgrade Legacy Peripherals
Interfacing Microcontrollers To USB
USB to RS-232 / RS-485 Converters
Interfacing RF Modules To USB
USB Smart Card Readers
ORDERING INFORMATION
USB Modems
PART #
DESCRIPTION
Robotics
SDM-USB-QS-S
USB Module
USB Instrumentation
MDEV-USB-QS
Master Development Kit
USB Game Controllers
USB-to-Serial Converter Cables
Revised 1/28/08
ELECTRICAL SPECIFICATIONS
Parameter
POWER SUPPLY
Operating Voltage
Supply Current
UART SECTION
Data Rate
Data Output:
Logic Low
Logic High
EEPROM Size
USB SECTION
Data Output:
Logic Low
Logic High
Single-Ended RX Threshold
Differential Common Mode
Differential Input Sensitivity
Driver Output Impedance
ENVIRONMENTAL
Operating Temperature Range
V
CC
I
CC
4.35
–
5.0
26.0
5.25
28.0
VDC
mA
–
–
Designation
Min.
Typical
Max.
Units
Notes
PIN DESCRIPTIONS
Pin #
Name
Description
1
–
V
OL
V
OH
0.3
3.2
–
0.4
4.1
–
0.6
4.9
1,024
VDC
VDC
Bits
–
–
–
0.0003
–
3.0
Mbps
–
USBDP
USB data signal plus
2
USBDM
USB data signal minus
3
UV
OL
UV
OH
UV
SE
UC
OM
UV
DIF
UD
RVZ
–
0.0
–
+70
0.0
2.8
0.8
0.8
0.2
29
–
–
–
–
–
–
0.3
3.6
2.0
2.5
–
44
VDC
VDC
VDC
VDC
VDC
Ω
–
–
–
–
–
–
–
GND
4
5
V
CC
Ground supply
Positive power supply
Goes low during USB Suspend Mode. This pin can be used to
SUSP_IND power down external logic when the host puts the USB bus
into suspend mode.
6
RX_IND
°
C
This line will pulse low when receiving data from the USB bus.
This allows for the connection of a LED indicator.
7
TX_IND
VDC
VDC
mA
°C
°C
ABSOLUTE MAXIMUM RATINGS
Supply Voltage V
CC
Any Input or Output Pin
Max Current Sourced By Outputs
Operating Temperature
Storage Temperature
Soldering Temperature
-0.5
to
+6.0
-0.5
to V
CC
+ 0.5
24
0
to
+70
-65
to
+150
+225°C for 10 seconds
This line will pulse low when transmitting data on the USB
bus. This allows for the connection of a LED indicator.
8
485_TX
Transmit enable line for RS-485 applications
9
DTR
Data Terminal Ready control / handshake output
*NOTE*
Exceeding any of the limits of this section may lead to permanent
damage to the device. Furthermore, extended operation at these maximum
ratings may reduce the life of this device.
10
CTS
Clear To Send control / handshake input
*CAUTION*
This product incorporates numerous static-sensitive components.
Always wear an ESD wrist strap and observe proper ESD handling
procedures when working with this device. Failure to observe this
precaution may result in module damage or failure.
11
RTS
Request To Send control / handshake output
12
DATA_OUT
Transmit asynchronous data output
PIN ASSIGNMENTS
1
2
3
4
5
6
7
8
USBDP
RI
DCD
USBDM
GND
DSR
VCC
DATA_IN
SUSP_IND DATA_OUT
RX_IND
RTS
TX_IND
CTS
485_TX
DTR
16
15
14
13
12
11
10
9
13
DATA_IN
Receive asynchronous data input
14
DSR
Data Set Ready control / handshake input
15
DCD
Data Carrier Detect control / input
16
Figure 2: SDM-USB-QS-S Pinout (Top View)
Page 2
RI
Ring Indicator control input
Page 3
PAD LAYOUT
The following pad layout diagram is designed to facilitate both hand and
automated assembly.
AUTOMATED ASSEMBLY
0.065"
For high-volume assembly, most users will want to auto-place the modules. The
modules have been designed to maintain compatibility with reflow processing
techniques; however, due to the their hybrid nature, certain aspects of the
assembly process are far more critical than for other component types.
Following are brief discussions of the three primary areas where caution must be
observed.
0.610"
0.070"
0.100"
Figure 3: Recommended PCB Layout
Reflow Temperature Profile
PRODUCTION GUIDELINES
The modules are housed in a hybrid SMD package that supports hand or
automated assembly techniques. Since the modules contain discrete
components internally, the assembly procedures are critical to ensuring the
reliable function of the modules. The following procedures should be reviewed
with and practiced by all assembly personnel.
Temperature (
o
C)
The single most critical stage in the automated assembly process is the reflow
stage. The reflow profile below should not be exceeded, since excessive
temperatures or transport times during reflow will irreparably damage the
modules. Assembly personnel will need to pay careful attention to the oven’s
profile to ensure that it meets the requirements necessary to successfully reflow
all components while still remaining within the limits mandated by the modules.
The figure below shows the recommended reflow oven profile for the modules.
300
Recommended RoHS Profile
Max RoHS Profile
255°C
250
235°C
217°C
200
185°C
180°C
150
125°C
100
Recommended Non-RoHS Profile
HAND ASSEMBLY
Pads located on the bottom of the
module are the primary mounting
surface. Since these pads are
inaccessible during mounting,
castellations that run up the side of
the module have been provided to
facilitate solder wicking to the
module’s underside. This allows for
very quick hand soldering for
prototyping and small volume
production.
Soldering Iron
Tip
Solder
PCB Pads
Castellations
Figure 4: Soldering Technique
50
0
30
60
90
120
150
180
210
240
270
300
330
360
Time (Seconds)
Figure 19: Maximum Reflow Profile
If the recommended pad guidelines have been followed, the pads will protrude
slightly past the edge of the module. Use a fine soldering tip to heat the board
pad and the castellation, then introduce solder to the pad at the module’s edge.
The solder will wick underneath the module, providing reliable attachment. Tack
one module corner first and then work around the device, taking care not to
exceed the times listed below.
Shock During Reflow Transport
Since some internal module components may reflow along with the components
placed on the board being assembled, it is imperative that the modules not be
subjected to shock or vibration during the time solder is liquid. Should a shock
be applied, some internal components could be lifted from their pads, causing
the module to not function properly.
Washability
Absolute Maximum Solder Times
Hand-Solder Temp. TX +225°C for 10 Seconds
Hand-Solder Temp. RX +225°C for 10 Seconds
Recommended Solder Melting Point +180°C
Reflow Oven: +220°C Max. (See adjoining diagram)
Page 4
The modules are wash resistant, but are not hermetically sealed. Linx
recommends wash-free manufacturing; however, the modules can be subjected
to a wash cycle provided that a drying time is allowed prior to applying electrical
power to the modules. The drying time should be sufficient to allow any moisture
that may have migrated into the module to evaporate, thus eliminating the
potential for shorting damage during power-up or testing. If the wash contains
contaminants, the performance may be adversely affected, even after drying.
Page 5
MODULE DESCRIPTION
The Linx SDM-USB-QS-S module will convert USB signals from a host, such as
a PC or hub, into TTL logic level signals. This enables the module to be
connected directly to microcontrollers (or Linx RF modules for wireless
applications) or to RS-232 or RS-485 level converters for communication with
legacy devices. The module handles all of the complicated enumeration and bus
communication processes, freeing the designer to focus on handling the data. All
necessary firmware is included in the module and the device descriptors can
easily be changed to customize the device.
VCC
GND
THEORY OF OPERATION
Figure 7 below shows a block diagram of the QS module.
SUSP_IND
TX Buffer
128 Bytes
DATA_OUT
DATA_IN
RTS
USBDP
USBDM
CTS
USB
Transceiver
The host application software can access the USB device by simple, custom
functions or by standard Windows Win32 API calls. In addition, Virtual COM Port
drivers are available that make the USB module appear to the PC as an
additional COM port, without the need for additional system resources, such as
an IRQ or address. This allows the designer to program the application software
to use standard serial or parallel ports and then simply select the port that
represents the USB module. The drivers will automatically direct the data to the
USB bus and the device.
Serial Interface
Engine (SIE)
USB Protocol
Engine
UART FIFO
Controller
DTR
UART
DSR
DCD
RI
485_TX
TX_IND
RX_IND
USB DPLL
RX Buffer
384 Bytes
INSTALLING THE DRIVERS
The drivers for the USB module are included with the module’s
development system or may be downloaded from the Linx website at
www.linxtechnologies.com. These drivers should be downloaded onto the hard
drive of a PC or onto a disk. When the module is attached to the PC for the first
time, Windows will automatically detect the device and search for the best driver.
Windows will prompt for the location of the drivers, so browse to the folder or the
disk, click Next, and Windows will do the rest. Windows XP may return an error
window as shown in the figure below.
Clock
Figure 7: SDM-USB-QS-S Block Diagram
The USB transceiver block provides the physical interface for the USB signalling.
The USB DPLL locks onto the NRZ data and provides separate recovered clock
and data signals to the Serial Interface Engine (SIE).
The SIE performs the parallel-to-serial and serial-to-parallel conversion, bit-
stuffing / un-stuffing, and CRC calculations on the USB data.
The USB Protocol Engine manages the data from the USB control endpoint, the
USB protocol requests from the USB host controller, and the commands for
controlling the functional parameters of the UART.
Data from the USB data out endpoint is stored in the TX buffer and removed from
the buffer to the UART transmit register under control of the UART FIFO
controller.
Data from the UART receive register is stored in the RX buffer prior to being
removed by the SIE on a USB request for data from the device data in endpoint.
The UART FIFO controller handles the transfer of data between the RX and TX
buffers and the UART transmit and receive registers.
Figure 6: Windows XP Driver Error Window
This window is simply a warning that the driver has not gone through Microsoft’s
certification process and could potentially pose a problem for the system. The
drivers provided for the QS module have been independently tested and should
not pose any problems unless modified by the user. Click the Continue Anyway
button to finish the installation process.
The UART performs asynchronous 7 / 8 bit parallel-to-serial and serial-to-parallel
conversion of the data on the RS-232 interface. Control signals supported by the
UART include RTS, CTS, DSR , DTR, DCD, and RI. The UART provides a
transmitter-enable control signal (485_TX) to assist with interfacing to RS-485
transceivers. The UART supports RTS / CTS, DSR / DTR and X-On / X-Off
handshaking options. Handshaking, where required, is handled in hardware to
ensure fast response times. The UART also supports the RS-232 BREAK setting
and detection conditions.
Page 6
Page 7
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 V
CC
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.
VCC
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.
0.1uF
+
USB Type B
Connector
12
+
USB Type B
Connector
GND
DAT+
DAT -
5V
4
3
2
1
GND
GSHD
GSHD
SDM-USB-QS-S
1
USBDP
RI
DCD
DSR
DATA_IN
DATA_OUT
RTS
CTS
DTR
9
10
11
12
13
14
15
USBDM
GND
VCC
SUSP_IND
RX_IND
TX_IND
485_TX
16
2
3
4
5
6
7
8
0.1uF
6.3V
0.1uF
16V
C1+
14
15
+
11
VCC
V+
C1-
+
13
0.1uF
6.3V
GND
DAT+
DAT -
5V
4
3
2
1
GND
SDM-USB-QS-S
1
USBDP
2
RI
16
RI
6
GSHD
GSHD
5
MAX213
C2+
16
TX DATA
DTR
RTS
7
6
20
21
CTS
DCD
DSR
RX DATA
RI
VCC
GND
3
V-
C2-
T1
IN
T2
IN
T3
IN
T4
IN
8
5
26
22
19
24
SUSP_IND
USBDM
17
+
DCD
15
DCD
4
GND
DSR
14
DSR
0.1uF
16V
T1
OUT
T2
OUT
T3
OUT
T4
OUT
R1
OUT
R2
OUT
R3
OUT
R4
OUT
R5
OUT
EN
25
SHDN
GND
10
R1
IN
R2
IN
R3
IN
R4
IN
R5
IN
2
3
1
28
9
4
27
23
18
VCC
DATA_IN
13
RX DATA
GND GND
SUSP_IND
5
GND
6
SUSP_IND
DATA_OUT
12
TX DATA
RX_IND
RTS
11
RTS
7
6
5
TX DATA2
8
TX_IND
CTS
10
CTS
DTR2
485_TX
DTR
9
DTR
GND GND
RTS2
220
220
VCC
DCD2
1
DSR2
6
CTS2
TX DATA2
2
DCD2
RTS2
7
Figure 8: USB Bus-Powered Schematic
DSR2
RX DATA2
3
RX DATA2
CTS2
8
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.
RI2
DTR2
4
RI2
9
5
DB9M
Figure 9: RS-232 To USB Converter
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.
Page 8
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.
RXM-XXX-ES
1
VCC
2
3
4
5
1
TXM-XXX-ES
PDN
ANT
LVL ADJ
GND
LOW V DET
/CLK SEL
/CLK
GND
DATA
10
9
8
7
6
VCC
8
NC
NC
NC
NC
PDN
RSSI
DATA
AUDIO
AREF
NC
16
15
14
13
12
11
10
9
USB Type B
Connector
GND
DAT+
DAT -
5V
GSHD
GSHD
GND
6
5
GND
VCC
220
1
2
3
4
5
6
7
8
SDM-USB-QS-S
USBDP
RI
USBDM
DSR
GND
VCC
SUSP_IND DATA_OUT
RX_IND
RTS
TX_IND
CTS
485_TX
DTR
GSHD
GSHD
16
15
14
USB Type B
Connector
GND
12
11
10
9
DAT+
DAT -
5V
4
3
2
GND
GND GND
VCC
220
1
2
3
4
5
6
7
8
SDM-USB-QS-S
USBDP
RI
USBDM
DCD
DSR
GND
VCC
DATA_IN
SUSP_IND DATA_OUT
RX_IND
RTS
TX_IND
CTS
485_TX
DTR
16
15
14
13
12
11
10
9
6
TX Side
5
RX Side
Figure 10: Wireless Modem Using ES Series RF Modules
Page 9
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