TXM-900-HP3-SPO Linx Technologies Inc, TXM-900-HP3-SPO Datasheet - Page 7

• Manufacturer Part Number: TXM-900-HP3-SPO
• Description: RF Modules & Development Tools RF Transmitter 900MHz 8-CH SMD Pack
• Manufacturer: Linx Technologies Inc

Specifications of TXM-900-HP3-SPO

• Board Size: 32 mm x 16 mm x 3.8 mm
• Minimum Frequency: 902.62 MHz
• Minimum Operating Temperature: - 30 C
• Supply Voltage (min): 2.8 V
• Product: RF Modules
• Maximum Frequency: 927.62 MHz
• Supply Voltage (max): 17 V
• Maximum Operating Temperature: + 85 C
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

PROTOCOL GUIDELINES
INTERFERENCE CONSIDERATIONS
Page 12
While many RF solutions impose data formatting and balancing requirements,
Linx RF modules do not encode or packetize the signal content in any manner.
The received signal will be affected by such factors as noise, edge jitter, and
interference, but it is not purposefully manipulated or altered by the modules.
This gives the designer tremendous flexibility for protocol design and interface.
Despite this transparency and ease of use, it must be recognized that there are
distinct differences between a wired and a wireless environment. Issues such as
interference and contention must be understood and allowed for in the design
process. To learn more about protocol considerations, we suggest you read Linx
Application Note AN-00160.
Errors from interference or changing signal conditions can cause corruption of
the data packet, so it is generally wise to structure the data being sent into small
packets. This allows errors to be managed without affecting large amounts of
data. A simple checksum or CRC could be used for basic error detection. Once
an error is detected, the protocol designer may wish to simply discard the corrupt
data or implement a more sophisticated scheme to correct it.
The RF spectrum is crowded and the potential for conflict with other unwanted
sources of RF is very real. While all RF products are at risk from interference, its
effects can be minimized by better understanding its characteristics.
Interference may come from internal or external sources. The first step is to
eliminate interference from noise sources on the board. This means paying
careful attention to layout, grounding, filtering, and bypassing in order to
eliminate all radiated and conducted interference paths. For many products, this
is straightforward; however, products containing components such as switching
power supplies, motors, crystals, and other potential sources of noise must be
approached with care. Comparing your own design with a Linx evaluation board
can help to determine if and at what level design-specific interference is present.
External interference can manifest itself in a variety of ways. Low-level
interference will produce noise and hashing on the output and reduce the link’s
overall range.
High-level interference is caused by nearby products sharing the same
frequency or from near-band high-power devices. It can even come from your
own products if more than one transmitter is active in the same area. It is
important to remember that only one transmitter at a time can occupy a
frequency, regardless of the coding of the transmitted signal. This type of
interference is less common than those mentioned previously, but in severe
cases it can prevent all useful function of the affected device.
Although technically it is not interference, multipath is also a factor to be
understood. Multipath is a term used to refer to the signal cancellation effects
that occur when RF waves arrive at the receiver in different phase relationships.
This effect is a particularly significant factor in interior environments where
objects provide many different signal reflection paths. Multipath cancellation
results in lowered signal levels at the receiver and, thus, shorter useful distances
for the link.
TYPICAL APPLICATIONS
Figure 14: HP3 Transmitter and MAX232 IC
Figure 15: HP3 Transmitter and Linx QS Series USB Module
4.7uF
The figure below shows a typical RS-232 circuit using the HP3 Series transmitter
and a Maxim MAX232. The MAX232 converts RS-232 compliant signals to a
serial data stream, which the transmitter then sends. The MODE line is
grounded, so the channels are selected by the DIP switches.
The figure below shows a circuit using the QS Series USB module. The QS
converts USB compliant signals from a PC to serial data to be sent to the
transmitter. The MODE line is high, so the module is in Serial Channel Select
Mode. The RTS and DTR lines are used to load the channels. Application Note
AN-00155 shows sample source code that can be adapted to use on a PC. The
QS Series Data Guide and Application Note AN-00200 discuss the hardware
and software set-up required for QS Series modules.
The transmitter can also be connected to a microcontroller, which will generate
the data based on specific actions. A UART may be employed or an I / O line
may be “bit banged” to send the data to the transmitter. The transmitter may be
connected directly to the microcontroller without the need for buffering or
amplification.
C4
USB-B CONNECTOR
4.7uF
C5
4.7uF
GND
C3
+
4.7uF
C1
GND
+
GND
+
+
VCC
DAT+
DAT -
GND
5V
1
2
3
4
5
6
7
8
4
3
1
MAX232
C1+
V+
C1-
C2+
C2-
V-
T2OUT
R2IN
GND
GND
1
2
3
4
5
6
7
8
T1OUT
R1OUT
R2OUT
SDM-USB-QS
GND
R1IN
T1IN
T2IN
VCC
USBDP
USBDM
GND
VCC
SUSP_IND
RX_IND
TX_IND
485_TX
16
15
14
13
12
11
10
9
GND
DATA_OUT
DATA_IN
VCC
GND
+
DCD
DSR
DTR
RTS
CTS
C2
4.7uF
RI
GND
16
15
14
13
12
11
10
1
6
2
7
3
8
4
9
5
9
DB-9
VCC
GND
VCC
GND
11
12
1
2
3
4
5
6
7
9
TXM-900-HP3
GND
ANT
GND
NC
CS0
CS1 / SS CLOCK
CS2 / SS DATA
CTS
PDN
VCC
MODE
DATA
10
11
12
1
2
3
4
5
6
7
8
9
TXM-900-HP3
GND
ANT
GND
NC
CS0
CS1 / SS CLOCK
CS2 / SS DATA
CTS
PDN
VCC
MODE
DATA
GND
GND
NC
NC
NC
NC
NC
NC
NC
NC
24
23
22
21
20
19
18
14
13
GND
GND
GND
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
Page 13
24
23
22
21
20
19
18
17
16
14
13
GND