RXM-315-LR_1 Datasheet, PDF (5/11 Pages) List of Unclassifed Manufacturers – LR SERIES RECEIVER MODULE DATA

PROTOCOL GUIDELINES
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.
INTERFERENCE CONSIDERATIONS
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.
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TYPICAL APPLICATIONS
Figure 12 shows a circuit using the Linx LICAL-DEC-MS001 decoder. This chip
works with the LICAL-ENC-MS001 encoder to provide simple remote control
capabilities. The decoder will detect the transmission from the encoder, check for
errors, and if everything is correct, the encoder’s inputs will be replicated on the
decoder’s outputs. This makes sending key presses very easy.
SWITCHED OUTPUT
VCC
RELAY
VCC
1
10k 2.2k 2
3
4
5
6
7
8
9
220 10
D6
D7
SEL_BAUD0
SEL_BAUD1
GND
GND
LATCH
RX_CNTL
TX_ID
MODE_IND
GND
LICAL-DEC-MS001
D5
D4
D3
D2
VCC
VCC
D1
D0
DATA_IN
LEARN
20
19
18
17
VCC
16
15
14
13
12
11
100k
1
2
3
VCC
4
5
6
GND ⁷
8
NC
NC
NC
GND
VCC
PDN
RSSI
DATA
RXM-LR
GND
ANT
GND
NC
NC
NC
NC
NC
NC
16
15
14
13
12
11
10
9
GND
Figure 12: LR Receiver and MS Decoder
Figure 13 shows a typical RS-232 circuit using the LR receiver and a Maxim
MAX232 chip. The LR will output a serial data stream and the MAX232 will
convert that to RS-232 compliant signals.
VCC
VCC
C1
4.7uF
C3 ⁺
4.7uF
C4 ⁺
4.7uF
C5
4.7uF
MAX232
1
2
C1+
V+
4
5
C1-
C2+
VCC
GND
16
15
7
8
V-
T2OUT
R2IN
+ C2
4.7uF
1
GND
6
2
DB-9
3
8
9
5
GND
GND
GND
Figure 13: LR Receiver and MAX232 IC
RXM-XXX-LR-S
NC
ANT ¹⁶
2 _NC
GND ¹⁵
NC ¹⁴
VCC
NC ¹³
C
NC ¹²
NC ¹¹
RSSI
NC ¹⁰
8 _DATA
NC ⁹
GND
Figure 14 shows an example of combining the LR Series receiver with a Linx
SDM-USB-QS-S USB module. The LR will output a serial data stream and the
USB module will convert that to low-speed USB compliant signals.
USB-B
GND ⁴
DAT+
SDM-USB-QS-S
1 _USBDP
DAT -
5V
2 _USBDM
GND 3 _GND
4 _VCC
GND GND
5 _{SUSP_IND}
6 _{RX_IND}
7 _{TX_IND}
8 _{485_TX}
RI ¹⁶
15
DTR
RXM-XXX-LR-S
1 _NC
ANT ¹⁶
2
GND ¹⁵
NC ¹⁴
VCC
NC ¹³
C
NC ¹²
NC ¹¹
NC ¹⁰
DATA
NC ⁹
GND
Figure 14: LR Receiver and Linx USB Module
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