1 radio frequency receiving and dispatching chip
nRF401
NRF401 is Norwegian Nordic VLSI Corporation newest
promoted single chip RF transceiver, specially for in 433MHz ISM
(industry, scientific research and medical service) the frequency band
work designs. It is the present integration rate maximum non-
line number passes on the product. This chip integrated high
frequency function and so on launch, high frequency receive, PLL
synthesis, FSK modulation, FSK demodulation, double frequency channel
cut, has the performance outstanding, the power loss is low,
characteristic and so on easy to operate. The nRF401 periphery
part are very few, about only 10. Only includes a 4MHz datum
crystal oscillator (to be possible with the MCU sharing), a PLL ring
circuit filter and a VCO inductance, the dual-mode antenna gathers
one, has not debugged the part, this has brought enormous convenient
for the development and the production. The main technical
characteristic see Table 1 to show, its internal structure like chart
1 shows.
The nRF401 receiver use has the stronger antijamming ability the
FSK frequency-shift keying (Frequency-ShiftKeying) to modulate the
way, improved under the noise environment system performance;
Uses the DSS+PLL frequency synthesis technology, the work
频率稳定 is reliable. Moves the key modulation with ASK
(Amplitude-ShiftKeying) and the OOK switch key modulation (On-Off
Keying) the way compares, this way communication range is broader,
specially has the similar equipment work in neighbor the situation.
Chart 1 nRF401 interior diagram
Outside nRF401 does not need to meet expensively changes
accommodates the diode outside, but other competition products mostly
need to meet change accommodate the diode, the sound surface wave
filter component and so on. After these chips generally need to
carry on Manchester to code can transmit, meets a need higher skill
and the experience in the programming, need more memories and the
procedure capacity, and Manchester codes greatly reduces the data
transmission the efficiency, generally only can achieve the nominal
speed (actual speed) 1,/3, therefore greatly increased the software
work load and the product development difficulty. But the nRF401
series unique technology may directly transmit the monolithic
integrated circuit string mouth data, the application and the
programming extremely simple, antijamming ability strong, transmission
efficiency very high, also the use is very convenient.
NRF401 uses the small 20 pins SSOP seal, the base pin number and
the volume is smallest, uses the extremely compact electric circuit
board layout, is advantageous to reduces the PCB area, reduces the
cost, suits the portable product the design, also is advantageous to
the development and the production. 3V direct-current power
supply power supply. Receive electric current low, is only 11mA,
moreover when is examining (Polling) in turn the pattern may the
method which suspends through the periodicity cause it to be lower,
lengthens the battery life. It also provides further reduces the
current consumption to wait for an opportunity the pattern.
Table 2 for its part of base pins explanation.
The nRF401 another count for much characteristic is the receiver
frequency band 外阻?is very high (out-of-band blocking), this
meant it does not need exterior surface wave (SAW) the filter.
In addition the nRF401 demodulator is the DC balance, therefore
may use any kind of agreement, also may use each kind of '0', the '1'
sequence, thus does not need to waste the monolithic integrated
circuit precious processing resources to carry on Manchester to code.
The nRF401 string mouth may with any monolithic integrated
circuit connection, also does not need to carry on the establishment,
the application and the programming extremely simple, but the direct
transmission string mouth data, the transmission efficiency is very
high, is one kind can conveniently and each kind of monolithic
integrated circuit coordination use plan.
2 audio frequency connections chip TLV320AIC10
TLV320AIC10 is low power loss ?- Delta 16 A/D, the
D/A audio frequency connection which TI Corporation recent years newly
promoted (AIC) the chip. The simulation connection chip (AIC)
called the modulation demodulation arranges the decoding (modem Codec)
by it highly unprogrammability, the high performance, the low power
loss, the less periphery component, becomes current pronunciation
processing the mainstream product. Is suitable to audio
frequency processing, the pronunciation strengthens, pronunciation
security, echo counterbalance, VoIP (Voice-over-Internet Protocol) and
so on widespread telephone or in pronunciation application. Its
function formidable serial interface and enables TLV320AIC10 using the
support as well as the low power loss characteristic to become the
audio frequency application the best simulation connection.
TLV320AIC10 is one is general, 3 - 5.5V Codec, the interior
integrated 16 A/D and the D/A switch. Some two groups analog
input channel, a group analog output channel and a pair of digital I/O
mouth. Uses when the internal FIR filter sampling speed most Gao
Keda 22ksps, uses outside the piece when the FIR filter its sampling
speed most Gao Keda 88ksps, the work way and the sampling speed may
program the establishment by the monolithic integrated circuit.
In front of its internal ADC has anti- mixes folds the filter,
has the sampling filter afterwards, in front of DAC has the
interpolation filter, the receive and the transmission may also carry
on, also the input output gain control is programmable, may work in
单端 or the difference way. Its unique direct DCSI parameter
establishment pattern uses the single track serial mouth directly to
the internal register programming, not data conversion serial mouth
influence. The event controls the pattern to cause the
monolithic integrated circuit to be possible to monitor like the
telephone RING/OFF-HOOK examination and so on the external event.
AIC10 controls the register control by 5. Among them,
controls register 1: Software repositions, DAC 16 or 15 + 1
pattern choice as well as anti- mixes folds the filter, the sampling
filter, the interpolation filter enables/the bypass choice.
Controls register 2: Decision work way and sampling speed.
Controls register 3: Software turns off light, the
simulation and the digital signal feedback and the event control the
pattern choice; ADC 16 or 15 + 1 pattern choice. Controls
register 4: Input output gain control. The AIC
initialization mainly is carries on the hypothesis to these 4
registers parameter. This component and the monolithic
integrated circuit connection is easy to realize, the development and
the use is more convenient. Especially suits applies to the low
bit rate, the high performance crowded equipment voice transmission,
the recognition and the synthesis and so on each kind of VOIP, the
electric cable modem, the pronunciation and the telephone domain.
3 systems hardware connections
The receive/transmitter should satisfy the portable
battery power supply equipment some basic requests, can be suitable
for the wireless RF application. These basic requests are:
Plan cost low, volume small, low power loss, conforms to the
battery power supply requirement, the integration rate high, does not
need the trimming exterior part, the periphery part extremely few, the
processing is easier, data output rate high, transmission time
shorter, the connection is simple, may and the inexpensive monolithic
integrated circuit connection. This article designs the wireless
colony pronunciation transmission system by monolithic radio frequency
receiving and dispatching chip and so on chip nRF401, micro controller
MSP430F1121, TLV320AIC10, EPM7128S is composed. Its system
hardware connection like chart 2 shows.
MSP430F1121 is the ultra low power loss micro controller which
TI Corporation produces, has 16 RISC structure, 16 CPU register and
the constant register, 4KB ROM, 256B FLASH, 256B RAM, instruction
cycle time 125ns, the ultra low working voltage (1.8V-3.6V), the ultra
low power consumption (1.3uA-160uA), has 5 kind of provinces
electricity pattern, but serial on-line programming, procedure code by
encryption melt silk protection. May see from the chart, the
micro controller is systematic "is in charge of", is responsible to
move the agreement, controls nRF401 the receiving and dispatching
condition, completes arranges the decoding, and movement system
application software and hardware, thus saves the cost and the space.
In the electric circuit E2PROM uses in to deposit the
transmitting frequency jump the order and the coded data, RAM uses in
to deposit needs the data which the micro controller processes.
Uses the 1.5V battery power supply, because the system power
supply is 3V, therefore completes the power source by a DC/DC
converter the transformation, in order to avoid DC/DC transforming the
power source the noise to have the influence to the correspondence,
uses the LC filter.
NRF401 is receives the launch to gather a chip, then take
receives the data also to be allowed the firing data, the work way as
the half-duplex. Therefore this electric circuit is the
transmission circuit also is the accepting circuit. When has the
key presses down is the state of action, the voice signal makes the
A/D transformation after TLV320AIC10, gives under the MSP430F1121
control the data nRF401, launches it. Presses down without the
pressed key when for receive condition.
When chip use, first carries on the establishment through the
micro controller to the chip interior register, hypothesis parameter
and so on operating frequency, emissive power; After enters the
normal work condition, according to needs to carry on the receiving
and dispatching transformation control, the transmission/receive data
through the micro controller or carries on the phase transition.
Working pattern like table 3 shows.
Table 3 working patterns establishment
EPM7128S uses for the combinatory logic which provides
the overall system to need. It belongs to the MAX7000 series, is
Altera Corporation based on second-generation MAX structure CPLD.
It provides reaches 5,000 to be possible to use the gate and to
program in the system, quickly reaches 6ns its pin to the pin time
delay. May hold variously, independent combinatory logic and
succession logic function. EPM7128S has 2 working voltages, the
nuclear voltage is 5V, the I/O working voltage may suppose is 5V or
3.3V. When supposes is 3.3V, its input bears 5V, but outputs is
3.3V the TTL level (all drivers can dispose in 3.3V and 5V, permission
uses in to mix in voltage system). The EPM7128S merit is it
based on E2PROM, may carry on the on-line programming through the JTAG
mouth, the designer may design the content through to download from PC
machine the electric cable and the JTAG mouth carries on to EPM7128S
wilfully time revises. Uses EPM7128S in here is provides the
combinatory logic for the electric circuit to map the space. It
has reaches 100 I/O pin to be possible to supply the programming use,
the convenient system expansion storage space and outside supposes.
When programming should pay attention the question is: The
nRF401 communication speed most is high is 22Kbit/s; The receive
pattern transforms into launch pattern switching time at least 1ms;
May transmit the free length the data; The launch pattern
transforms into the receive pattern switching time at least is 3ms.
When waits for an opportunity the pattern, the electric circuit
enters the readiness for action, the electric circuit does not receive
and the firing data. When low power loss pattern, the electric
circuit could not enter the active status, the electric circuit does
not receive and the firing data. Waits for an opportunity the
pattern and the low power loss pattern transforms into the launch
pattern switching time at least is 3ms; Waits for an opportunity
the pattern and the low power loss pattern transforms into receive
pattern switching time at least 2ms.
4 composite signals PCB design attention question
A good printed circuit board (PCB) designs regarding
obtains the good RF performance is essential, this system designs with
two plywood. Because nRF401 periphery part few, was the present
integration rate highest RF receiving and dispatching chip and
integrated baseband processing, the design quite conveniently, but
actual as a result of the high-frequency circuit characteristic, the
operating frequency was higher (UHF), also nRF401 the PCB design was
the composite signal circuit design, although nRF401 already greatly
simplified the radio frequency circuit design and the request, when
design still needed the extremely attention. Below generally
speaking has the principle to need to follow:
(1) when wiring cannot only consider the line whether cloth does
pass, if the PCB wiring layout is unreasonable, possibly can greatly
affect the performance and the signal distance, this is the RF circuit
design characteristic decision. Therefore divides into PCB the
radio frequency circuit and the control circuit two parts of
arrangement. PCB uses the double kneading board, divides into
the part surface and the bottom surface. The bottom surface
continual has to meet the ground, the part surface meets the ground
guarantee part full earth, massive passes the hole link part surface
to meet the ground and the bottom surface meets the ground.
(2) appropriate components layout. The radio frequency
circuit part surface take nRF401 as a center, various parts abut its
periphery, reduces the distribution parameter as far as possible the
influence. Needs to explain is the VCO inductance layout is
count for much, a process optimizes the VCO inductance layout will be
allowed to give the PLL ring circuit filter to provide an appropriate
voltage. The matching network primary device best approaches
nRF401 ANT1 and ANT2, reduces the stray inductance and the stray
capacity.
(3) are partial the PCB district for the independent simulation
part and the numeral. In in electric circuit board all levels,
the digital signal only can in the electric circuit board digital
partial wiring, the simulated signal only be able in the electric
circuit board simulation partial wiring, and simulates the power
source and the digital power source must divide. The nRF401
direct current power supply essential is leaving the VDD foot near
place to go to the lotus root as far as possible with the high
performance RF electric capacity. If a small electric capacity
again and on a bigger electric capacity effect can be better (2.2uF).
The radiofrequency component power source and the digital
circuit partial power sources separation, nRF401 VSS straightforward
receives one after another meets the ground.
(4) the radio frequency circuit power source use high
performance radio frequency electric capacity 去, 去 the
electric capacity approaches nRF401 as far as possible the VDD end,
generally also pastes in a larger capacity surface installs nearby the
electric capacity the parallel small value electric capacity.
NRF401 power source essential process very good filter, and
separates with the digital circuit power supply.
When (5) wiring, the power line and the grounding must be as far
as possible thick. Besides reduces the pressure drop, more
importantly reduces the coupling noise. The crystal introduces
which from the monolithic integrated circuit walks the line not to be
able to leave the data line or the pilot wire too is near. Pays
attention to the power source the filter and the power line walks the
line. Cannot introduces the digital signal or the control signal
on the PLL return route filter element. When wiring reduces the
circle as far as possible the area, reduces the induced noise.
(6) uses the correct wiring rule. Should avoid the long
power source on the PCB board walking the line, all parts grounding,
the VDD ties, VDD goes to the lotus root electric capacity to have to
nRF401 as far as possible near, if the PCB design top layer has the
shop copper, the VSS foot essential connects the shop copper surface,
if the PCB design first floor has the shop copper, welds the plate
with VSS to have a hole to be connected can obtain a better
performance. All switches digital signal and the control signal
all cannot pass through the PLL ring circuit filter element and nearby
the VCO inductance.
(7) fully considers the power source to nRF401 the influence.
The power source can complete, entire electric circuit
antijamming has solved one most. The RF electric circuit is
very sensitive to the power source noise, must give the RF power
source to add the filter circuit, reduces the power source noise to
the RF electric circuit disturbance. For instance, may use the
magnetism bead and the electric capacity composition П filter
circuit, natural condition request Gao Shiye cannot use the inductance
to replace the magnetism bead. ----- The author introduces Master Chen hungmuy tea female
Xi'an electron scientific and technical university communication
engineering institute the graduate student, specialized direction for
correspondence and information system
Associate Professor Chen Jiannan Xi'an electron
scientific and technical university communication engineering
institute mainly studies the direction for software radio, signal
processing |
