P9222-R/RN Datasheet

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28

May 5, 2022

Receiver-to-transmitter communication is accomplished by modulating the load applied to the receiver; i.e., amplitude-shift keying (ASK). To

the transmitter, this appears as an impedance change, which results in measurable variations of the transmitter’s output waveform. Modulation

is done with AC modulation, using internal switches to connect external capacitors from AC1 and AC2 to ground.

The P9222-R/RN communicates with the base station by sending ASK communication packets to WPC transmitters. Each communication

packet has the following structure:

Figure 22. Communication Packet Structure

Preamble

Header

Message

Checksum

7.4 Bit Encoding Scheme for ASK

As required by the WPC specification, the P9222-R/RN uses a differential bi-phase encoding scheme to modulate data bits onto the power

signal. A clock frequency of 2kHz is used for this purpose. A logic ONE bit is encoded using two narrow transitions, whereas a logic ZERO bit

is encoded using two wider transitions as shown in Figure 23.

Figure 23. WPC Packet Example with Reference Clock Shown

t CLK

ONE

ZERO

ONE

ZERO

ONE

ONE

ZERO

ZERO

Each byte in the communication packet comprises 11 bits in an asynchronous serial format, as shown in Figure 24. Each byte has a start bit,

8 data bits, a parity bit, and a single stop bit.

Figure 24. Byte Encoding Scheme

Start

Stop

Parity

b0

1

2

3

4

5

6

7

b

b

b

b

b

b

b