IEC 63563-5:2025

IEC 63563-5 ®
Edition 1.0 2025-06
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Qi Specification version 2.0 –
Part 5: Communications Physical Layer

Spécification Qi version 2.0 –
Partie 5 : Couche physique des communications
ICS 29.240.99, 35.240.99 ISBN 978-2-8327-0539-1

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- 2 - IEC 63563-5:2025 © IEC 2025
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
QI SPECIFICATION VERSION 2.0 –
Part 5: Communications Physical Layer
FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising all
national electrotechnical committees (IEC National Committees). The object of IEC is to promote international co-
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technical committees; any IEC National Committee interested in the subject dealt with may participate in this
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participate in this preparation. IEC collaborates closely with the International Organization for Standardization
(ISO) in accordance with conditions determined by agreement between the two organizations.
2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
consensus of opinion on the relevant subjects since each technical committee has representation from all
interested IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
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Publication and the corresponding national or regional publication shall be clearly indicated in the latter.
5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity
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6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
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8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) IEC draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). IEC takes no position concerning the evidence, validity or applicability of any claimed patent rights in respect
thereof. As of the date of publication of this document, IEC had not received notice of (a) patent(s), which may be
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not be held responsible for identifying any or all such patent rights.
IEC 63563-5 has been prepared by technical area 15: Wireless Power Transfer, of IEC
technical committee 100: Audio, video and multimedia systems and equipment. It is an
International Standard.
It is based on Qi Specification version 2.0, Communications Physical Layer and was submitted
as a Fast-Track document.
The text of this International Standard is based on the following documents:
Draft Report on voting
100/4250/FDIS 100/4280/RVD
Full information on the voting for its approval can be found in the report on voting indicated in
the above table.
The language used for the development of this International Standard is English.
The structure and editorial rules used in this publication reflect the practice of the organization
which submitted it.
This document was developed in accordance with ISO/IEC Directives, Part 1 and ISO/IEC
Directives, IEC Supplement available at www.iec.ch/members_experts/refdocs. The main
document types developed by IEC are described in greater detail at www.iec.ch/publications.
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under webstore.iec.ch in the data related to the
specific document. At this date, the document will be
• reconfirmed,
• withdrawn, or
• revised.
- 4 - IEC 63563-5:2025 © IEC 2025
WIRELESS POWER
CONSORTIUM
Qi Specification
Communications Physical Layer
Version 2.0
April 2023
DISCLAIMER
The information contained herein is believed to be accurate as of the date of publication,
but is provided “as is” and may contain errors. The Wireless Power Consortium makes no
warranty, express or implied, with respect to this document and its contents, including any
warranty of title, ownership, merchantability, or fitness for a particular use or purpose.
Neither the Wireless Power Consortium, nor any member of the Wireless Power
Consortium will be liable for errors in this document or for any damages, including indirect
or consequential, from use of or reliance on the accuracy of this document. For any further
explanation of the contents of this document, or in case of any perceived inconsistency or ambiguity
of interpretation, contact: info@wirelesspowerconsortium.com.
RELEASE HISTORY
Specification Version Release Date Description
v2.0 April 2023 Initial release of the v2.0 Qi Specification.

- 6 - IEC 63563-5:2025 © IEC 2025
Table of Contents
1  General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1 Structure of the Qi Specification. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
1.2 Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.3 Compliance. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.4 References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.5 Conventions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.6 Power Profiles. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
2  Load Modulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
2.1 Modulation scheme . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
2.2 Bit encoding scheme . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
2.3 Byte encoding scheme . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
2.4 Data packet structure. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
3  Frequency-shift keying . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
3.1 Modulation scheme . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
3.2 Bit encoding scheme . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
3.3 Byte encoding scheme . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
3.4 Data packet structure. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
3.5 Response Pattern . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

1 General
The Wireless Power Consortium (WPC) is a worldwide organization that aims to develop and
promote global standards for wireless power transfer in various application areas. A first
application area comprises flat-surface devices such as mobile phones and chargers in the
Baseline Power Profile (up to 5 W) and Extended Power Profile (above 5 W).
1.1 Structure of the Qi Specification
General documents
 Introduction
 Glossary, Acronyms, and Symbols
System description documents
 Mechanical, Thermal, and User Interface
 Power Delivery
 Communications Physical Layer
 Communications Protocol
 Foreign Object Detection
 NFC Tag Protection
 Authentication Protocol
- 8 - IEC 63563-5:2025 © IEC 2025
1.2 Scope
The Communications Physical Layer (this document) defines the low-level (physical layer and the
data link layer) formats of data bits, data bytes, and data packets. In addition, it provides
requirements and guidelines for load modulation and frequency-shift keying.
1.3 Compliance
All provisions in the QiSpecification are mandatory, unless specifically indicated as recommended,
optional, note, example, or informative. Verbal expression of provisions in this Specification follow
the rules provided in ISO/IEC Directives, Part 2.
Table 1: Verbal forms for expressions of provisions
Provision Verbal form
requirement “shall” or “shall not”
recommendation “should” or “should not”
permission “may” or “may not”
capability “can” or “cannot”
1.4 References
For undated references, the most recently published document applies. The most recent WPC
publications can be downloaded from http://www.wirelesspowerconsortium.com.

1.5 Conventions
1.5.1 Notation of numbers
 Real numbers use the digits 0 to 9, a decimal point, and optionally an exponential part.
 Integer numbers in decimal notation use the digits 0 to 9.
 Integer numbers in hexadecimal notation use the hexadecimal digits 0 to 9 and A to F, and are
prefixed by "0x" unless explicitly indicated otherwise.
 Single bit values use the words ZERO and ONE.
1.5.2 Tolerances
Unless indicated otherwise, all numeric values in the QiSpecification are exactly as specified and do
not have any implied tolerance.
1.5.3 Fields in a data packet
A numeric value stored in a field of a data packet uses a big-endian format. Bits that are more
significant are stored at a lower byte offset than bits that are less significant. Table 2 and Figure 1
provide examples of the interpretation of such fields.
Table 2: Example of fields in a data packet
b b b b b b b b
7 6 5 4 3 2 1 0
(msb)
B
16-bit Numeric Data Field
B
(lsb)
B Other Field (msb)
B 10-bit Numeric Data Field (lsb) Field
Figure 1. Examples of fields in a data packet
16-bit Numeric Data Field
b b b b b b b b b b b b b b b b
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
B B
0 1
10-bit Numeric Data Field
b b b b b b b b b b
9 8 7 6 5 4 3 2 1 0
B B
2 3
- 10 - IEC 63563-5:2025 © IEC 2025
1.5.4 Notation of text strings
Text strings consist of a sequence of printable ASCII characters (i.e. in the range of 0x20 to 0x7E)
enclosed in double quotes ("). Text strings are stored in fields of data structures with the first
character of the string at the lowest byte offset, and are padded with ASCII NUL (0x00) characters
to the end of the field where necessary.
EXAMPLE: The text string “WPC” is stored in a six-byte fields as the sequence of characters 'W', 'P', 'C', NUL,
NUL, and NUL. The text string “M:4D3A” is stored in a six-byte field as the sequence 'M', ':', '4', 'D',
'3', and 'A'.
1.5.5 Short-hand notation for data packets
In many instances, the QiSpecification refers to a data packet using the following shorthand
notation:
/
In this notation, refers to the data packet's mnemonic defined in the QiSpecification,
Communications Protocol, and refers to a particular value in a field of the data packet.
The definitions of the data packets in the QiSpecification, Communications Protocol, list the
meanings of the modifiers.
For example, EPT/cc refers to an End Power Transfer data packet having its End Power Transfer
code field set to 0x01.
1.6 Power Profiles
A Power Profile determines the level of compatibility between a Power Transmitter and a Power
Receiver. Table 3 defines the available Power Profiles.
 BPP PTx: A Baseline Power Profile Power Transmitter.
 EPP5 PTx: An Extended Power Profile Power Transmitter having a restricted power transfer
()pot
capability, i.e. P = 5 W.
L
 EPP PTx: An Extended Power Profile Power Transmitter.
 BPP PRx: A Baseline Power Profile Power Receiver.
 EPP PRx: An Extended Power Profile Power Receiver.
Table 3: Capabilities included in a Power Profile
Feature BPP PTx EPP5 PTx EPP PTx BPP PRx EPP PRx
Ax or Bx design Yes Yes No N/A N/A
MP-Ax or MP-Bx design No No Yes N/A N/A
Baseline Protocol Yes Yes Yes Yes Yes
Extended Protocol No Yes Yes No Yes
Authentication N/A Optional Yes N/A Optional

- 12 - IEC 63563-5:2025 © IEC 2025
2 Load Modulation
This section defines both the physical layer and the data link layer of the Power Receiver to Power
Transmitter communications interface.
The Power Receiver communicates to the Power Transmitter using backscatter modulation. For
this purpose, the Power Receiver modulates the amount of power that it draws from the Power
Signal. The Power Transmitter detects this as a modulation of the current through and/or voltage
across the Primary Cell. In other words, the Power Receiver and Power Transmitter use an
amplitude modulated Power Signal to provide a Power Receiver to Power Transmitter
communications channel.
2.1 Modulation scheme
The Power Receiver shall modulate the amount of power that it draws from the Power Signal, such
that the Primary Cell current and/or Primary Cell voltage assume two states, namely a HI state and
a LO state. A state is characterized in that the amplitude is constant within a certain variation Δ for
at least t ms. If the Power Receiver is properly aligned to the Primary Cell of a type A10 or MP-A1
S
Power Transmitter, and for all appropriate loads, at least one of the following three conditions shall
apply:
 The difference of the amplitude of the Primary Cell current in the HI and LO state is at least
15 mA.
 The difference of the Primary Cell current in the HI and LO state is at least 15 mA. The Primary
Cell current is measured at instants in time that correspond to one quarter of the cycle of the
control signal driving the half-bridge inverter.
 The difference of the amplitude of the Primary Cell voltage in the HI and LO state is at least
200 mV.
During a transition, the Primary Cell current and Primary Cell voltage are undefined. See Figure 2
and Table 4.
The HI and LO states do not correspond to fixed Primary Cell current and/or Primary Cell voltage
levels.
The design requirements of the Mobile Device determine both the range of lateral displacements
that constitute proper alignment and the range of loading conditions on its Power Receiver.
The start of the cycle corresponds the closing of the top switch in the half-bridge inverter.

Figure 2. Amplitude modulation of the Power Signal
t t
S S
t
t T
T
t
S
t
HI state HI state S
LO state LO state
Modulation
Δ
depth
Δ
100%
Table 4: Amplitude modulation of the Power Signal
Parameter Symbol Value Unit
Maximum transition time t 100 µs
T
150 µs
Minimum stable time t
S
Current amplitude variation Δ 8mA
Voltage amplitude variation Δ 110 mV
Primary Cell current
Primary Cell voltage
- 14 - IEC 63563-5:2025 © IEC 2025
2.2 Bit encoding scheme
The Power Receiver shall use a differential bi-phase encoding scheme to modulate data bits onto
the Power Signal. For this purpose, the Power Receiver shall align each data bit to a full period t
CLK
of an internal clock signal, such that the start of a data bit coincides with the rising edge of the clock
signal. This internal clock signal shall have a frequency f = (2 ± 4%) kHz.
CLK
NOTE: A ripple on the Power Receiver’s load yields a ripple on the Power Transmitter’s current. As a result,
such a ripple can lead to bit errors in the Power Transmitter. The number of bit errors can be
particularly high if this ripple has a frequency that is close to the modulation frequency f .
CLK
The Receiver shall encode a ONE bit using two transitions in the Power Signal, such that the first
transition coincides with the rising edge of the clock signal and the second transition coincides with
the falling edge of the clock signal. The Receiver shall encode a ZERO bit using a single transition in
the Power Signal, which coincides with the rising edge of the clock signal.
Figure 3. Example of a differential bi-phase encoding scheme
t
CLK
ONE ZERO ONE ZERO ONE ONE ZERO ZERO

2.3 Byte encoding scheme
The Power Receiver shall use an 11-bit asynchronous serial format to transmit a data byte. This
format consists of a start bit, the 8 data bits of the byte, a parity bit, and a single stop bit. The start bit
is a ZERO. The order of the data bits is LSB first. The parity bit is odd. This means that the Power
Receiver shall set the parity bit to ONE if the data byte contains an even number of ONE bits.
Otherwise, the Power Receiver shall set the parity bit to ZERO. The stop bit is a ONE. Figure 4
shows the data byte format—including the differential bi-phase encoding of each individual
bit—using the value 0x35 as an example.
Figure 4. Example of the asynchronous serial format
Start b0 b1 b2 b3 b4 b5 b6 b7 Parity Stop

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2.4 Data packet structure
The Power Receiver shall communicate to the Power Transmitter using data packets. As shown in
Figure 5, a data packet consists of 4 parts, namely a preamble, a header, a message, and a checksum.
The preamble consists of a minimum of 11 and a maximum of 25 bits, all set to ONE, and encoded
as defined in Section 2.1, Modulation scheme. The preamble enables the Power Transmitter to
synchronize with the incoming data and accurately detect the start bit of the header.
The header, message, and checksum consist of a sequence of three or more bytes encoded as
defined in Section 2.3, Byte encoding scheme.
Figure 5. data packet format
Preamble Header Message Checksum
The Power Transmitter shall consider a data packet as received correctly if:
 The Power Transmitter has detected at least 4 preamble bits that are followed by a start bit.
 The Power Transmitter has not detected a parity error in any of the bytes that comprise the
data packet. This includes the header byte, the message bytes, and the checksum byte.
 The Power Transmitter has detected the stop bit of the checksum byte.
 The Power Transmitter has determined that the checksum byte is consistent (see Section
2.4.3, Checksum).
If the Power Transmitter does not receive a data packet correctly, the Power Transmitter shall
discard the data packet and not use any of the information contained therein.
NOTE: In the ping phase as well as in the identification and configuration phase, this typically leads to a time-
out, which causes the Power Transmitter to remove the Power Signal.
The Power Receiver should turn off its communications modulator after transmitting a data
packet. This may cause an additional HI state to LO state or LO state to HI state transition in the
Primary Cell current.
2.4.1 Header
The header consists of a single byte that indicates the data packet type. In addition, the header
implicitly provides the size of the message contained in the data packet. The number of bytes in a
message is calculated from the value contained in the header of the data packet, as shown in the
center column of Table 5.
Table 5: Message size
*
Header Message Size Comment
0x00…0x1F 1 + (Header – 0) / 32 1 ×32 messages (size 1)
0x20…0x7F 2 + (Header – 32) / 16 6 × 16 messages (size 2…7)
0x80…0xDF 8 + (Header – 128) / 8 12 × 8 messages (size 8…19)
0xE0…0xFF 20 + (Header – 224) / 4 8 × 4 messages (size 20…27)
*
Values in this column are truncated to an integer.
2.4.2 Message
The Power Receiver shall ensure that the message contained in the data packet is consistent with
the data packet type indicated in the header. See Qi Specification, Communications Protocol for a
detailed definition of the possible messages. The first byte of the message, byte B , directly follows
the header.
2.4.3 Checksum
The checksum consists of a single byte that enables the Power Transmitter to check for
transmission errors. The Power Transmitter shall calculate the checksum as follows:
C:=HB⊕⊕⊕B …⊕B
0 1 last
where C represents the calculated checksum, H represents the header byte, and B , B ,…, B
0 1 last
represent the message bytes.
If the calculated checksum C and the checksum byte contained in the data packet are not equal, the
Power Transmitter shall determine that the checksum is inconsistent.

- 18 - IEC 63563-5:2025 © IEC 2025
2.4.4 Correct reception of a data packet
A Power Transmitter shall decide that it has received a data packet correctly if and only if:
 the start bit and stop bits of each data byte are correct;
 the parity bit of each data byte is correct; and
 the checksum value at the end of the data packet is correct.
If the Power Transmitter has not received a data packet correctly, it shall discard the data packet
and proceed as if it had not received the latter.
NOTE: The above requirement implies that a Power Transmitter does not respond to simple-query data
packets or to data-request data packets that are incorrectly received.
2.4.5 Start and end of a data packet
Figure 6 zooms in on the start and end of a data packet, showing a number of preamble data bits, the
first start bit, and the final stop bit. The reference time for the start of a data packet is the edge at the
start of the first start bit (a ZERO). The reference time for the end of a data packet is the edge at the
center of the final stop bit (a ONE).
After transmitting a data packet containing an odd number of data bytes, the communications signal
contains an additional edge. This additional edge is not a part of the data packet; it results from the
Power Receiver switching off its modulator.
Figure 6. Start and end of a load-modulated data packet
Even - length data packet
preamble start bit stop bit
Modulator
ON
OFF
Reference time Reference time
for the start of for the end of
the data packet the data packet
Odd - length data packet
preamble start bit stop bit
Modulator
ON
OFF
Reference time Reference time Note: spurious
for the start of for the end of edge when the
the data packet the data packet PRx switches off
its modulator
3 Frequency-shift keying
The Power Transmitter communicates to the Power Receiver using Frequency Shift Keying, in
which the Power Transmitter modulates the Operating Frequency of the Power Signal.
This section defines both the physical layer and the data link layer of the Power Transmitter to
Power Receiver communications interface. The data link layer supports both data packets and
Responses. The format of a data packet is defined in Section 3.3, Byte encoding scheme. The format
of a Response is defined in Section 3.5, Response Pattern.
3.1 Modulation scheme
The Power Transmitter shall switch its Operating Frequency between the Operating Frequency f
op
in the unmodulated state and the Operating Frequency f in the modulated state. The difference
mod
between these two frequencies is characterized by two parameters:
 Polarity. This parameter determines whether the difference between f and f is positive or
mod op
negative.
NOTE: In both the Configuration data packet and a Specific Request data packet that has its Request field
set to 0x03 (FSK Parameters), the Power Receiver encodes the positive polarity as a ZERO and the
negative polarity as a ONE. In addition, note that a negative polarity typically increases the voltage
induced in the Secondary Coil, and therefore should be used with care.
 Depth. This parameter determines the magnitude of the difference between f and f .
op mod
NOTE: Both the Configuration data packet and the Specific Request data packet (Request 0x03, FSK
Parameters) encode the modulation depth in a two-bit unsigned integer value.
For any given Operating Frequency f , and depending on the polarity and depth parameters, f
op mod
shall be chosen such that the time difference between a single cycle of f and a single cycle of f is
mod op
in the range that is defined in Table 6.
NOTE: The minimum time difference in this Table corresponds to a single cycle of a 32 MHz clock.

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Table 6: FSK States
1 1
--------- – ------
f f
mod op
Polarity Depth Minimum Maximum Unit
positive 3 -282.00 -249.00 ns
positive 2 -157.00 -124.00 ns
positive 1 -94.50 -61.50 ns
positive 0 -63.25 -30.25 ns
negative 0 30.25 63.25 ns
negative 1 61.50 94.50 ns
negative 2 124.00 157.00 ns
negative 3 249.00 282.00 ns
3.2 Bit encoding scheme
The Power Transmitter shall use a differential bi-phase encoding scheme to modulate data bits in
the Power Signal. For this purpose, the Power Transmitter shall align each data bit to the number
of cycles contained in the Power Transfer Contract (default 512).
The Power Transmitter shall encode a ONE bit using two transitions in the Power Signal frequency.
The first transition shall occur at the start of the bit and the second transition shall occur at half the
number of cycles per bit (default 256). The Transmitter shall encode a ZERO bit using a single
transition in the Power Signal frequency at the start of the bit.
Figure 7. Example of differential bi-phase encoding
512 cycles 256 cycles
ONE ZERO ONE ZERO ONE ONE ZERO ZERO
A Power Receiver shall be resilient to variations in the number of cycles per half bit of plus or
minus ceil(Ncycles/200), where ceil(x) represents the smallest integer larger than x. For example, a
Power Receiver shall be able to decode FSK data bits encoded using any number of Power Signal
cycles ranging from 253 to 259, inclusive if the number of cycles per bit is 512 (see Table 7).
Table 7 lists the NCYCLES containing number of samples and allowed variation.
Table 7: Resilience to variations in the number of cycles per half bit
NCycles Minimum Target Maximum
512 253 256 259
256 126 128 130
128 63 64 65
64 31 32 33
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3.3 Byte encoding scheme
The Power Transmitter shall use an 11-bit asynchronous serial format to transmit a data byte. This
format consists of a start bit, the 8 data bits of the byte, a parity bit, and a single stop bit. The start bit
is a ZERO. The order of the data bits is LSB first. The parity is even, which means that the Power
Transmitter shall set the parity bit to ONE if the data byte contains an odd number of ONE bits.
Otherwise, the Power Transmitter shall set the parity bit to ZERO.
NOTE: For clarity, Power Receiver to Power Transmitter communications use odd parity, as defined in the Qi
Specification, Power Delivery.
The stop bit is a ONE. Figure 8 shows the data byte format—including the differential bi-phase
encoding of each individual bit—using the value 0x35 as an example. The Power Transmitter shall
send all bits in a contiguous sequence without a pause in between two consecutive bits. It shall
send the start bit first and the stop bit last.
Figure 8. Example of the asynchronous serial format
Start b0 b1 b2 b3 b4 b5 b6 b7 Parity Stop

3.4 Data packet structure
The Power Transmitter shall communicate to the Power Receiver using data packets. A data packet
consists of a series of bytes that the Power Transmitter shall send as a contiguous sequence, i.e.
there shall be no pauses in between two consecutive bytes. Section 3.4.1, Header defines the format
of a byte. As shown in Figure 9, a data packet consists of three parts, a header, a message, and a
checksum. The header, message, and checksum consist of a sequence of three or more bytes
encoded as defined in Section 3.4.1, Header.
Figure 9. Data packet format
Header Message Checksum
The Power Receiver shall consider a data packet as received correctly if:
 The Power Receiver has not detected a parity error in any of the bytes that comprise the data
packet. This includes the header byte, the message bytes and the checksum byte.
 The Power Receiver has detected the stop bit of the checksum byte.
 The Power Receiver has determined that the checksum byte is consistent (see Section 3.4.3,
Checksum).
If the Power Receiver does not receive a data packet correctly, the Power Receiver shall discard the
data packet and not use any of the information contained therein.
3.4.1 Header
The header consists of a single byte that indicates the data packet type. In addition, the header
implicitly provides the size of the message contained in the data packet. The number of bytes in a
message is calculated from the value contained in the header of the data packet, as is shown in the
center column of Table 8.
Table 8: Message size
Header Message Size* Comment
0x00 to 0x1F 1 + (Header – 0) / 32 1 ×32 messages (size 1)
0x20 to 0x7F 2 + (Header – 32) / 16 6 × 16 messages (size 2 to 7)
0x80 to 0xDF 8 + (Header – 128) / 8 12 × 8 messages (size 8 to 19)
0xE0 to 0xFF 20 + (Header – 224) / 4 8 × 4 messages (size 20 to 27)
*
Values in the Message Size column are truncated to an integer.

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3.4.2 Message
The Power Transmitter shall ensure that the message contained in the data packet is consistent
with the data packet type indicated in the header. See Qi Specification, Communications Protocol for
a detailed definition of the possible messages. The first byte of the message, byte B , directly follows
the header.
3.4.3 Checksum
The checksum consists of a single byte that enables the Power Receiver to check for transmission
errors. The Power Transmitter shall calculate the checksum as follows,
C:=HB⊕⊕⊕B …⊕B
0 1 last
where C represents the calculated checksum, H represents the header byte, and B , B ,…, B
0 1 last
represent the message bytes.
If the calculated checksum C and the checksum byte contained in the data packet are not equal, the
Power Receiver shall determine that the checksum is inconsistent.
3.4.4 Correct reception of a data packet
A Power Receiver shall decide that it has received a data packet correctly if and only if:
 the start bit and stop bits of each data byte are correct;
 the parity bit of each data byte is correct; and
 the checksum value at the end of the data packet is correct.
If the Power Receiver has not received the data packet correctly, it shall discard the data packet and
proceed as if it had not received the latter.
3.4.5 Start and end of a data packet
Figure 10 zooms in on the start and end of a data packet, showing the first start bit and the final
stop bit. The reference time for the start of a data packet is the edge at the start of the first start bit
(a ZERO). The reference time for the end of a data packet is the edge at the center of the final stop
bit (a ONE).
Figure 10. Start and end of an FSK data packet
start bit stop bit
f
mod
f
op
Reference time Reference time
for the start of for the end of
the data packet
the data packet
3.5 Response Pattern
When a Power Receiver sends a simple query data packet (see Qi Specification, Communications
Protocol for the classification of data packets a Power Receiver can send), the Power Transmitter
responds with a Response Pattern. Table 9 and Figure 11 define the four possible eight-bit
Response Patterns.
NOTE: Unlike a data byte, a Response Pattern does not include a start bit, a parity bit, and a stop bit. Due to its
structure, a Power Receiver can use relatively simple decoding logic to distinguish between the
Response Patterns.
Table 9: Response Patterns
Response Pattern Description
ACK Acknowledge
NAK Not acknowledge
ND Not defined
ATN Attention
Figure 11. Format of the Response Patterns
b b b b b b b b
0 1 2 3 4 5 6 7
Modulated
ACK
Unmodulated
ONE ONE ONE ONE ONE ONE ONE ONE
Reference time Reference time
for the start of the for the end of the
Response Pattern Response Pattern
NAK
ZERO ZERO ZERO ZERO ZERO ZERO ZERO ZERO
ND
ONE
ONE ZERO ONE ZERO ZERO ONE ZERO
ATN
ONE ONE ZERO ZERO ONE ONE ZERO ZERO
time
Reference time Reference time
for the start of the for the end of the
Response Pattern Response Pattern

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COMMISSION ÉLECTROTECHNIQUE INTERNATIONALE
____________
SPÉCIFICATION QI VERSION 2.0 –

Partie 5: Couche physique des communications

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