Texas Instruments BoosterPack BOOST-IR, Руководство пользователя

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5HFHLYHU¶V
MCU
Demodulation
TA0
CCR2
TA1
CCR2
Carrier
Envelope
Modulated
0
1
0
1
From UCA0TXD/UCA0SIMO
SYSCFG1.IRDATA
SYSCFG1.IRDSSEL SYSCFG1.IRPSEL
P1.0/UCA0TXD/UCA0SIMO
SYSCFG1.IRMSEL
1
0
0
1
1
0
SYSCFG1.IREN
0
1
IR Modulation (SYS)
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TI Design and Software Examples
Figure 9. ASK IR Generation on MSP430FR4133
3.1.1.3 ASK Demodulation
The receiver uses a photodiode to convert the IR light to current. A transimpedance amplifier is frequently
used to convert the current into voltage, which passes through a gain amplifier and filter before
demodulation, which removes the carrier signal. Then the demodulated signal, which is essentially just the
envelope signal now that the carrier has been removed, can be connected directly the MCU for decoding
(see
Figure 10 ).
Figure 10. IR Demodulation
The BOOST-IR BoosterPack features a Vishay TSOP59348 IR Receiver device. This device performs all
of the steps above, stripping off the carrier signal, and then provides the envelope directly to the FR4133
TA0.2 input. The Timer A0 module is then used in capture mode to record the edges of the signal. The
pulse length is calculated from these capture values to determine if a 0 or 1 was received using pulse
distance encoding.
3.1.1.4 Pulse Distance Encoding and Protocol
The software IR emitter and receiver examples included with this TI Design use a Pulse Distance protocol
for communication between two Laun BoosterPacks. This protocol is similar to that used on
many commercially available remote control devices. In Pulse Distance Encoding, each bit is a carrier
modulated pulse and a space – the carrier modulated pulse width is constant, while the width of the space
varies to indicate a logic 0 or logic 1.
13 SLAU598A – December 2014 – Revised July 2015 BOOST-IR Infrared (IR) BoosterPack™ Plug-in Module
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