P9221-R3 Datasheet

© 2017 Integrated Device Technology, Inc.

23

October 20, 2017

10. Bi-directional User Data Communication

In customer end systems, the transmitter and receiver boards need to have an external microcontroller (MCU) or leverage an existing application

processor to orchestrate bi-directional communication. Using the I2C communication, the MCU on the receiver board needs to load the data

into specific registers and trigger the communication. The P9221-R3 sends the data to the P9242-R3 using amplitude-shift keying (ASK)

modulation. The P9242-R3 will receive the data and interrupt the MCU on the transmitter when the data is ready to be read. The external MCU

on the transmitter follows the same procedure to send the data to the P9221-R3. When new data is available to be read, the P9221-R3 will

interrupt the external MCU on the receiver board.

Bi-directional user data communication is enabled only in the power transfer phase for the WPC standard. The external MCU on the receiver

board can read register 014AHEX to determine whether the P9221-R3 is in the power transfer phase. Register 014AHEX will be set to 5HEX when

the device is in the power transfer phase.

See Figure 25 for a state diagram that illustrates the procedure that the external MCU on the receiver board must follow to send the user data

from the P9221-R3 to the P9242-R3 as described in section 10.1. See Figure 26 for a state diagram that illustrates the procedure the external

MCU must follow to read the data sent by the P9242-R3 as described in section 10.2.

10.1 Transferring Data from the P9221-R3 to the P9242-R3

The external MCU on the receiver board should read bit 0 in register 004EHEX to determine the status of the communication channel before

initiating a new transfer. If the communication channel is free, bit 0 in register 004EHEX is 0. If the communication channel is busy, bit 0 in register

004EHEX is set to 1.

The P9221-R3 receiver supports sending up to 8 bytes of user data. The external MCU on the receiver should write the data that it will be

sending to the transmitter into outgoing data registers (0089HEX to 0090HEX) and set the Data Header register (0088HEX) accordingly. The Data

Header register (see Table 29) indicates the number of bytes that need to be transmitted. For example, if the external MCU on the receiver

intends to transfer 3 bytes of information, it should write 38HEX to register 0088HEX and write the user data into registers 0089HEX to 008BHEX.

The P9221-R3 will not transfer registers 008CHEX to 0090HEX when the header is set to 3 bytes. If the external MCU on the receiver will be

sending 8 bytes of information, it should write 88HEX to register 0088HEX and write the data into registers 0089HEX to 0090HEX.

Table 9.

Registers Used for Data Transmission from P9221-R3 to P9242-R3

Register

Register Address

Command Register

004EHEX

Data Header Register

0088HEX

Outgoing User Data Registers

0089HEX to 0090HEX (8 bytes)

WPC Power Transfer Phase Indicator

014AHEX

The external MCU on the receiver should set bit 0 in the Command register 004EHEX to 1 for triggering the communication after loading the user

data into the outgoing data registers and setting the data header for the correct number of bytes. After receiving the communication trigger from

the control register, the P9221-R3 reads the data header register and outgoing data registers and constructs a proprietary communication

packet with a packet checksum. The communication packet is sent into the channel between two Control Error Packets (CEP) using ASK

modulation.

Figure 23 shows the timing diagram for the user data transfer from the P9221-R3 to the P9242-R3.

Figure 23. Timing Diagram for a User Data Transfer from the P9221-R3 to the P9242-R3

CEP Packet

CEP Packet

Proprietary Communication Packets (ASK)