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THE DATA OUTPUT
The DATA line outputs recovered digital data. It is an open collector output with
an internal 4.7k Ω pull-up. When an RF transmission is not present, or when the
TIMING CONSIDERATIONS
There are four major timing considerations to be aware of when designing with
the HP3 Series receiver. These are shown in the table below.
received signal strength is too low to ensure proper demodulation, the data
output is squelched continuous high. This feature supports direct operation with
UARTs, which require their input to be continuously high. An HP3 transmitter and
receiver can be directly connected between two UARTs without the need for
buffering or logical inversion. It should be noted that the squelch level is set just
Parameter
T1
T2
T3
T4
Description
Time between DATA output transitions
Channel change time (time to valid data)
Receiver turn-on time via PDN
Receiver turn-on time via V CC
Max.
20.0mS
1.5mS
3.0mS
7.0mS
over the receiver’s internal noise threshold. Any external RF activity above that
threshold will “break squelch” and produce hashing on the line. While the DATA
line will be reliably squelched in low-noise environments, the designer should
always plan for the potential of hashing.
AUDIO OUTPUT
The HP3 Series is optimized for the transmission of serial data; however, it can
also be used very effectively to send a variety of analog signals, including audio.
The ability of the HP3 to send combinations of audio and data opens new areas
of opportunity for creative design.
The analog output of the AUDIO line is valid from 50 Hz to 28 kHz, providing an
AC signal of about 1V peak-to-peak. This is a high impedance output and not
suitable for directly driving low-impedance loads, such as a speaker. In
applications where a low impedance load is to be driven, a buffer circuit should
always be used. For example, in the case of a speaker, a simple op-amp circuit
such as the one shown below can be used to act as an impedance converter.
VCC
T1 is the maximum amount of time that can elapse without a data transition. Data
must always be considered in both the analog and the digital domain. Because
the data stream is asynchronous and no particular format is imposed, it is
possible for the data to meet the receiver’s data rate requirement yet violate the
analog frequency requirements. For example, if a 255 (0FF hex) were sent
continuously, the receiver would view the data as a DC level. It would hold that
level until a transition was required to meet the minimum frequency specification.
If no transition occurred, data integrity could not be guaranteed. While no
particular structure or balancing requirement is imposed, the designer must
ensure that both analog and digital signals meet the transition specification.
T2 is the worst-case time needed for a powered-up module to switch between
channels after a valid channel selection. This time does not include external
overhead for loading a desired channel in the serial channel-selection mode.
T3 is the time to receiver readiness from the PDN line going high. Receiver
readiness is determined by valid data on the DATA line. This assumes an
incoming data stream and the presence of stable supply on V CC .
T4 is the time to receiver readiness from the application of V CC . Receiver
readiness is determined by valid data on the DATA line. This assumes an
HP Analog Out
1uF
10k
2
3
–
+
6
4
5
LM386
250uF
0.05uF
10 ohm
incoming data stream and the PDN line is high or open.
RECEIVING DATA
Once an RF link has been established, the challenge becomes how to effectively
transfer data across it. While a properly designed RF link provides reliable data
transfer under most conditions, there are still distinct differences from a wired link
that must be addressed. Since the modules do not incorporate internal encoding
or decoding, the user has tremendous flexibility in how data is handled.
Figure 12: Audio Buffer Amplifier
The transmitter’s modulation voltage is critical, since it determines the carrier
deviation and distortion. The transmitter input level should be adjusted to
achieve the optimum results for your application in your circuit. Please refer to
the transmitter data guide for full details.
When used for audio, the analog output of the receiver should be filtered and
buffered to obtain maximum sound quality. For voice, a 3-4kHz low-pass filter is
often employed. For broader-range sources, such as music, a 12-17kHz cutoff
may be more appropriate. In applications that require high-quality audio, a
compandor may be used to further improve SNR. The HP3 is capable of
providing audio quality comparable to a radio or intercom. For applications where
true high fidelity audio is required, the HP3 will probably not be the best choice,
and a device optimized for audio should be utilized.
Page 8
It is important to separate the types of transmissions that are technically possible
from those that are legally allowed in the country of operation. Application Notes
AN-00126, AN-00140 and Part 15, Section 249 of the FCC rules should be
reviewed for details on acceptable transmission content in the U.S.
If you want to transfer simple control or status signals (such as button presses)
and your product does not have a microprocessor or you wish to avoid protocol
development, consider using an encoder / decoder IC set. These chips are
available from several manufacturers, including Linx. They take care of all
encoding and decoding functions and provide a number of data lines to which
switches can be directly connected. Address bits are usually provided for
security and to allow the addressing of multiple receivers independently. These
ICs are an excellent way to bring basic remote control products to market quickly
and inexpensively. It is also a simple task to interface with inexpensive
microprocessors or one of many IR, remote control, DTMF, or modem ICs.
Page 9
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相关PDF资料
MDEV-900-HP3-SPS-USB
KIT MASTER 900MHZ HP-3 USB SMD
MDEV-900-NT
TRM 900 NT MASTER DEV SYSTEM
MDEV-GPS-SG
KIT MASTER DEV GPS SG SERIES
MDEV-GPS-SR
KIT MASTER DEV GPS SR SERIES
MDEV-LICAL-HS-ES
KIT MASTER DEV HS ES RF MODULES
MDEV-USB-QS
KIT DEV MASTER USB QS SERIES
MF11-0010005
THERMISTOR NTC 100OHM -+5% PROBE
MF51E103F3950C
THERMISTOR NTC PREC -+1% 3950K
相关代理商/技术参数
MDEV-900HP3PPS-RS232
功能描述:射频开发工具 HP-3 Master Dev Sys Pinned, RS232 Module
RoHS:否 制造商:Taiyo Yuden 产品:Wireless Modules 类型:Wireless Audio 工具用于评估:WYSAAVDX7 频率: 工作电源电压:3.4 V to 5.5 V
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功能描述:射频开发工具 HP-3 Master Dev Sys Pinned, USB Module
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功能描述:KIT MASTER 900MHZ HP-3 RS232 SMD RoHS:是 类别:RF/IF 和 RFID >> RF 评估和开发套件，板 系列:- 标准包装:1 系列:- 类型:GPS 接收器 频率:1575MHz 适用于相关产品:- 已供物品:模块 其它名称:SER3796
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功能描述:射频开发工具 NT Series Dev kit w/ Transparent module
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