TXM-433-LC_ Linx Technologies Inc, TXM-433-LC_ Datasheet - Page 5

• Manufacturer Part Number: TXM-433-LC_
• Description: RF Modules & Development Tools RF Transmitter 433MHz
• Manufacturer: Linx Technologies Inc

Specifications of TXM-433-LC_

• Board Size: 12.7 mm x 9.1 mm x 3.3 mm
• Minimum Operating Temperature: - 40 C
• Supply Voltage (min): 2.1 V
• Product: RF Modules
• Maximum Frequency: 433.92 MHz
• Supply Voltage (max): 3.6 V
• Maximum Operating Temperature: + 85 C
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

PROTOCOL GUIDELINES
INTERFERENCE CONSIDERATIONS
Page 8
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 8: LR Transmitter and MS Encoder
Figure 9: LR Transmitter and MAX232 IC
Figure 10: LR Transmitter and Linx QS Series USB Module
4.7uF
VCC
GND
C4
2.7k
DATA
4.7uF
C5
4.7uF
USB-B
Figure 8 shows a circuit using a Linx MS Series encoder. This chip works with
the Linx LICAL-DEC-MS001 decoder to provide simple remote control
capabilities. The decoder detects the transmission from the encoder, checks for
errors, and if everything is correct, replicates the encoder’s inputs on its outputs.
This makes registering key presses very simple.
Figure 9 shows a typical RS-232 circuit using the LR transmitter and a Maxim
MAX232 chip. The MAX232 converts RS-232 compliant signals from a PC to a
serial data stream, which is then transmitted by the LR module.
Figure 10 shows an example of using the LR transmitter with a Linx QS Series
USB module. The USB module converts low-speed USB compliant signals from
a PC into a serial data stream, which is then transmitted by the LR module.
GND
C3
+
4.7uF
DAT -
1
2
3
4
DAT+
C1
GND
GND
+
TXM-xxx-LR
5V
+
GND
DATA IN
GND
IADJ/VCC
VCC
+
4
3
2
1
1
2
3
4
5
6
7
8
GND
GND
RF OUT
C1+
V+
C1-
C2+
C2-
V-
T2OUT
R2IN
GND
PDN
VCC
MAX232
1
2
3
4
5
6
8
7
R1OUT
R2OUT
8
7
6
5
T1OUT
USBDP
USBDM
GND
VCC
SUSP_IND
RX_IND
TX_IND
485_TX
GND
R1IN
VCC
VCC
T1IN
T2IN
SDM-USB-QS-S
16
15
14
13
12
11
10
9
GND
DATA
100k
100k
220
DATA_OUT
VCC
GND
DATA_IN
+
GND
C2
4.7uF
DCD
DSR
DTR
RTS
CTS
10
1
2
3
4
5
6
7
8
9
1
6
2
7
3
8
4
9
5
RI
LICAL-ENC-MS001
D6
D7
SEL_BAUD0
SEL_BAUD1
GND
GND
GND
TX_CNTL
DATA_OUT
MODE_IND
DB-9
16
15
14
13
12
11
10
9
VCC
VCC
GND
GND
750
GND
GND
CREATE_ADDR
750
1
2
3
4
GND
DATA
GND
LADJ/VCC
1
2
3
4
TXM-xxx-LR
SEND
GND
DATA
GND
LADJ/VCC
VCC
VCC
TXM-xxx-LR
D5
D4
D3
D2
D1
D0
20
19
18
17
16
15
14
13
12
11
GND
PDN
VCC
ANT
GND
PDN
VCC
ANT
8
7
6
5
8
7
6
5
100k
100k
100k
100k
100k
100k
100k
GND
VCC
GND
VCC
Page 9