AN1259

AN1259
KEELOQ® Microcontroller-based Code Hopping Encoder
Author:
Operation:
Enrique Aleman
Microchip Technology Inc.
INTRODUCTION
This application note describes the design of a
Microcontroller-based KEELOQ® Hopping Encoder.
This encoder is implemented on Microchip PIC16F636
microcontroller. A description of the encoding process,
the encoding hardware and description of the software
modules are included within this application note. The
software was designed to emulate an HCS365 dual
encoder. As it is, this design can be used to implement
a secure system transmitter that will have the flexibility
to be designed into various types of KEELOQ receiver/
decoders.
•
•
•
•
•
•
•
•
•
•
2.0-5.5V operation
Four button inputs
15 functions available
Four selectable baud rates
Selectable minimum code word completion
Battery low signal transmitted to receiver
Nonvolatile synchronization data
PWM, VPWM, PPM, and Manchester modulation
Button queue information transmitted
Dual Encoder functionality
DUAL ENCODER OPERATION
TRANSMITTER OVERVIEW
This firmware contains two transmitter configurations
with separate serial numbers, encoder keys,
discrimination values, counters and seed values. This
means that the transmitter can be used as two
independent systems. The SHIFT(S3) input pin is used
to select between encoder configurations. A low on this
pin will select Encoder 1, and a high will select Encoder 2.
As this is an emulation of the HCS365, the transmitter
has the following key features:
FUNCTIONAL INPUTS AND OUTPUTS
The software used in this implementation makes use of
the PIC16F636 internal encryption engine to generate
the hopping codes required for transmission.
The software implementation makes use of the
following pin designations:
Security:
•
•
•
•
•
•
Two programmable 32-bit serial numbers
Two programmable 64-bit encryption keys
Two programmable 60-bit seed values
Each transmitter is unique
67/69-bit transmission code length
32-bit hopping code
TABLE 1:
Label
S0
FUNCTIONAL INPUTS AND OUTPUTS
Pin Number
2 (RA5)
Input/Output
Function
Input
Switch Input S0
S1
3 (RA4)
Input
Switch input S1
S2
4 (RA3)
Input
Switch Input S2
S3
5 (RA2)
Input
Switch Input S3
RF_OUT
6 (RA1)
Output
Encoded transmitter signal output
LED
7(RA0)
Output
LED On/Off
© 2009-2011 Microchip Technology Inc.
DS01259B-page 1
AN1259
OPERATION FLOW DIAGRAM
FIGURE 1:
OPERATION FLOW
DIAGRAM
Start
Debounce Button
Inputs
Read
Configuration from
EEPROM
SAMPLE BUTTONS/WAKE-UP
Upon power-up, the transmitter verifies the state of the
buttons inputs and determines if a button is pressed. If
no button pressed is detected, the transmitter will go to
Sleep mode. The transmitter will wake up whenever a
button is pressed. Wake-up is achieved by configuring
the input port to generate an interrupt-on-change. After
the wake event, the input buttons are debounced for 20
ms to make a determination on which buttons have
been pressed. The button input values are then placed
in the transmission buffer, in the appropriate section.
LOAD SYSTEM CONFIGURATION
Sample Buttons/
Set Function_TX
A
Increment
Counter
After waking up and debouncing the input switches, the
firmware will read the system Configuration bytes.
These Configuration bytes will determine what data
and modulation format will be for the transmission.
All the system Configuration bytes are stored in the
EEPROM. Below is the EEPROM mapping for the
PIC16F636 transmitter showing the configuration and
data bits stored.
Encrypt Data
Load Transmit
Buffer/MTX/
Time-out Tie
Reset
Transmit: Buffer
+ 32 encrypted +3
open serial +
function code
Button
Time-out
No
New Button
Pressed?
Yes
A
No
Button Still
Pressed?
Yes
No
MTX = 0?
No
MTX = MTX-1
Yes
Sleep
DS01259B-page 2
© 2009-2011 Microchip Technology Inc.
AN1259
TABLE 2:
EEPROM MAPPING FOR THE PIC16F636 TRANSMITTER
Offset
Bytes
Bits
7
6
5
4
3
2
0x00
Sync Counter Transmitter #0, stored in Pseudo-Gray Code
0x01
Sync Counter Transmitter #0, stored in Pseudo-Gray Code
0x02
Sync Counter Transmitter #0, stored in Pseudo-Gray Code
0x03
Sync Counter Transmitter #0 Checksum AB
0x04
Sync Counter Transmitter #0 Checksum BC
0x05
Sync Counter Transmitter #0 Checksum AC
0x06
—
0x07
—
—
—
—
—
—
0x08
Sync Counter Transmitter #1, stored in Pseudo-Gray Code
0x09
Sync Counter Transmitter #1, stored in Pseudo-Gray Code
0x0A
Sync Counter Transmitter #1, stored in Pseudo-Gray Code
0x0B
Sync Counter Transmitter #1 Checksum AB
0x0C
Sync Counter Transmitter #1 Checksum BC
0x0D
Sync Counter Transmitter #1 Checksum AC
0x0E
—
0x0F
—
—
—
—
SD_FLG
0x10
32-BIT SERIAL NUMBER for TX#0 (MSB)
0x11
32-BIT SERIAL NUMBER for TX#0
0x12
32-BIT SERIAL NUMBER for TX#0
0x13
32-BIT SERIAL NUMBER for TX#0 (LSB)
0x14
4-BIT SEED CODE TX#0
60-BIT SEED VALUE (MSB) for TX #0
0x16
60-BIT SEED VALUE for TX #0
0x17
60-BIT SEED VALUE for TX #0
0x18
60-BIT SEED VALUE for TX #0
0x19
60-BIT SEED VALUE for TX #0
0x1A
60-BIT SEED VALUE for TX #0
0x1B
60-BIT SEED VALUE (LSB) for TX #0
STRTSEL_0
QUEN_0
XSER_0
HEADER_0
TMOD_0
0x1D
DISC_0 (Lower 8 bits)
0x1E
64-BIT KEY (MSB) for TX #0
0x1F
64-BIT KEY for TX #0
0x20
64-BIT KEY for TX #0
0x21
64-BIT KEY for TX #0
0x22
64-BIT KEY for TX #0
0x23
64-BIT KEY for TX #0
0x24
64-BIT KEY for TX #0
© 2009-2011 Microchip Technology Inc.
0
MNEMONIC
EE_CNT0
—
EE_VLOWL
EE_CNT1
TST_FLG
EE_SER
60-BIT SEED_0 VALUE (MS-NIBBLE)
0x15
0x1C
—
1
DISC_0 (MS-BITS)
EE_SEED
EE_DISC
EE_KEY
DS01259B-page 3
AN1259
TABLE 2:
EEPROM MAPPING FOR THE PIC16F636 TRANSMITTER (CONTINUED)
0x25
64-BIT KEY-0 (LSB) for TX #0
0x26
32-BIT SERIAL NUMBER for TX#1 (MSB)
0x27
32-BIT SERIAL NUMBER for TX#1
0x28
32-BIT SERIAL NUMBER for TX#1
0x29
32-BIT SERIAL NUMBER for TX#1 (LSB)
0x2A
4-BIT SEED CODE TX#1
60-BIT SEED_1 VALUE (MS-NIBBLE)
0x2B
60-BIT SEED VALUE (MSB) for TX#1
0x2C
60-BIT SEED VALUE for TX#1
0x2D
60-BIT SEED VALUE for TX#1
0x2E
60-BIT SEED VALUE for TX#1
0x2F
60-BIT SEED VALUE for TX#1
0x30
60-BIT SEED VALUE for TX#1
0x31
60-BIT SEED VALUE (LSB) for TX#1
0x32
DISC_1 (MS-BITS)
STRTSEL_1
QUEN_1
XSER_1 HEADER_1
0x33
DISC_1 (Lower 8 bits)
0x34
64-BIT KEY (MSB) for TX#1
0x35
64-BIT KEY for TX#1
0x36
64-BIT KEY for TX#1
0x37
64-BIT KEY for TX#1
0x38
64-BIT KEY for TX#1
0x39
64-BIT KEY for TX#1
0x3A
64-BIT KEY for TX#1
0x3B
64-BIT KEY (LSB) for TX#1
0x3C
0x3D
GSEL_0
LEDOS_1
0x3E
0x3F
LEDOS_0
DS01259B-page 4
BSEL_0
LEDBL_1
GSEL_1
LEDBL_0
TSEL
BSEL_1
PLLSEL
B_EE_SER
VLOWSEL
INDESEL
SDTM_1
VLOWL
B_EE_DISC
B_EE_KEY
SDTM_0
RFENO
TMOD_1
B_EE_SEED
CNTSEL
SDMD_0 SDLM_0
EE_CFG3
MTX
EE_CFG2
SDMD_1 SDLM_1
EE_CFG1
WAKE
EE_CFG0
© 2009-2011 Microchip Technology Inc.
AN1259
CONFIGURATION WORDS DESCRIPTION
TABLE 3:
TX0_CFG0 (FOR TRANSMITTER 0, FOR TRANSMITTER 1 USE TX1_CFG0)
BIT
Field
0
DISC:8
1
DISC:9
2
TMOD:0
3
TMOD:1
4
Description
Values
Upper two bits of Discrimination
Discrimination bits 9:8
Transmission Modulation Format
00
01
10
11
HEADER
Time Length of Transmission
Header
0 = 4*Te
1 = 10*Te
5
XSER
Extended Serial Number Select
0 = 28 bits
1 = 32 bits
6
QUEN
Queue Counter Enable
0 = Disable
1 = Enable
7
STRTSEL
Start/Stop Pulse Enable
0 = Disable
1 = Enable
TABLE 4:
=
=
=
=
PWM
Manchester
VPWM
PPM
TX0_CFG1 (FOR TRANSMITTER 0, FOR TRANSMITTER 1 USE TX1_CFG1)
BIT
Field
Description
Values
0
SDLM
Limited Seed Enable
0 = Disable
1 = Enable
1
SDMD
Seed Mode
0 = User
1 = Production
2
SDTM <3:2>
Time Before Seed Code Word
00 = 0.0 sec
01 = 0.8 sec
10 = 1.6 sec
11 = 3.2 sec
BSEL <5:4>
Transmission Baud Rate Select
00 = 100 µs
01 = 200 µs
10 = 400 µs
11 = 800 µs
GSEL <7:6>
Guard Time Select
00 = 0.0 ms
01 = 6.4 ms
10 = 51.2 ms
11 = 102.4 ms
3
4
5
6
7
© 2009-2011 Microchip Technology Inc.
DS01259B-page 5
AN1259
TABLE 5:
SYSCFG0
BIT
0
Field
Description
Values
WAKE <1:0>
Wake-up
00 = No wake-up
01 = 75ms 50%
10 = 50ms 33%
11 = 100ms 16.6%
2
CNTSEL
Counter Select
0 = 16 bits
1 = 20 bits
3
VLOWL
Low-Voltage Latch Enable
0 = Disable
1 = Enable
4
VLOWSEL
Low-Voltage Trip Level
0 = 2.2V
1 = 3.2V
5
PLLSEL
PLL interface Select
0 = ASK
1 = FSK
6
LEDBL_0
Low-Voltage LED Blink
0 = Continuous
1 = Once
7
LEDOS_0
LED On Time Select
0 = 50 ms
1 = 100 ms
1
TABLE 6:
SYSCFG1
BIT
0
Field
Description
Values
MTX <1:0>
Maximum Code Words
00 = 1
01 = 2
10 = 4
11 = 8
2
INDESEL
Dual Encoder Enable
0 = Disable
1 = Enable
3
RFEN0
RF Enable Output Select
0 = Disable
1 = Enable
4
TSEL
Time-out Select
00 = Disabled
01 = 0.8 sec
10 = 3.2 sec
11 = 25.6 sec
6
LEDBL_1
Low-Voltage LED Blink
0 = Continuous
1 = Once
7
LEDOS_1
LED On-Time Select
0 = 50 ms
1 = 100 ms
1
5
DS01259B-page 6
© 2009-2011 Microchip Technology Inc.
AN1259
SER_0 AND SER_1
COUNTER-CODE DESCRIPTION
SER_0 stores the 4 bytes of the 32-bit serial number for
transmitter 1 (SER_1 for transmitter 2). There are 32
bits allocated for the serial number and a selectable
Configuration bit determines whether 32 or 28 bits will
be transmitted. The serial number is meant to be
unique for every transmitter.
The following addresses save the counter checksum
values. The counter value is converted to Pseudo-Gray
code and stored in the Counter locations (COUNTA,
COUNTB, COUNTC) described on the EEPROM table.
These checksum values are used to validate the
current value of the counter and allows recovery from
any brown-out events. This code is contained in
module CounterCode.inc.
SEED_ 0 AND SEED_1
This is the 60-bit seed code that will be transmitted
when seed transmission is selected. SEED_0 for
transmitter 0 and SEED_1 for transmitter 1. This allows
for the implementation of the secure learning scheme.
KEY_0 (TRANSMITTER 0 64-BIT
ENCRYPTION KEY)
The 64-bit encryption key is used by the transmitter to
create the encrypted message transmitted to the
receiver. This key is created using a key generation
algorithm. The inputs to the key generation algorithm
are the secret manufacturer’s code, the serial number,
and/or the SEED value. The user may elect to use the
algorithm supplied by Microchip or to create their own
method of key generation.
ENCRYPTION ENGINE
The encryption portion of the firmware makes use of
the encryption engine internal to the PIC16F636. In
essence, the data to be encrypted is loaded into the
module, the number of cycles through the engine is set
and, after running, the encryption module places the
encrypted data into the registers CSRDATA<3:0>.
Please read technical Brief TB076, “Using the KEELOQ
Cryptographical Module” for more information on the
use of this module.
BUTTON PRESS DURING TRANSMIT
If the device is in the process of transmitting and
detects that a new button is pressed, the current
transmission will be aborted, a new code word will be
generated based on the new button information and
transmitted. If all the buttons are released, a minimum
number of code words will be completed. If the time for
transmitting the minimum code words is longer than the
time-out time, or the button is pressed for that long, the
device will time-out.
CODE TRANSMISSION FORMAT
The following is the data stream format transmitted:
TABLE 7:
DATA STREAM FORMAT TRANSMITTED
Unencrypted (bits)/Fixed Code
CRC (2 bits)
VLOW
(1 bit)
Repeat
(1 bit)
Function Code
(4 bits)
Encrypted (32 bits)
Serial Number
(28 bits)
Function Code
(4 bits)
Discrimination
(12 bits)
Counter
(16 bits)
Data transmitted LSb-first
A KEELOQ transmission consists of 32 bits of hopping
code data, 32 bits of fixed code data and 3 to 5 bits of
status information.
© 2009-2011 Microchip Technology Inc.
DS01259B-page 7
AN1259
HOPPING CODE PORTION
The hopping code portion is calculated by encrypting
the counter, discrimination value, and function code
with the Encoder Key (KEY). A new hopping code is
calculated every time a button press is pressed.
The synchronization counter can be either a 16- or a
10-bit counter as selected by the Counter Select option
(CNTSEL).
The discrimination value can be programmed with any
fixed value to serve as a post decryption check on the
receiver end.
FIXED CODE PORTION
The 32 bits of fixed code consist of 28 bits of serial
number and a copy of the 4-bit function code.
Each code word contains a preamble, header and data,
and is separated from another code by guard time. The
Guard Time Select (GSEL) configuration option can
select a time period of 0ms, 6.4ms, 51.2ms or 102.4ms.
All other timing specifications are based on the timing
element (Te). This Te can be set to 100 µs, 200 µs, 400
µs or 800 µs with the Baud Rate select (BSEL)
configuration. The calibration header time can be set to
4*Te or 10*Te with the Header Select (HEADER)
configuration option.
The firmware has four different transmission modulation formats available. The Modulation select (TMOD)
configuration option is used to select between:
•
•
•
•
FIGURE 2:
PULSE-WIDTH MODULATION (PWM)
FIGURE 3:
MANCHESTER (MAN)
DS01259B-page 8
Pulse-Width Modulation (PWM)
Manchester (MAN)
Variable Pulse-Width Modulation (VPWM)
Pulse Position Modulation (PPM)
© 2009-2011 Microchip Technology Inc.
AN1259
FIGURE 4:
VARIABLE PULSE-WIDTH MODULATION (VPWM)
FIGURE 5:
PULSE POSITION MODULATION (PPM)
If the Start/Stop Pulse Enable (STEN) configuration
option is enabled, the software will place a leading and
trailing ‘1’ on each code word. This bit is necessary for
modulation formats such as Manchester and PPM to
interpret the first and last data bit.
A receiver wake-up sequence can be transmitted
before the transmission starts. The wake-up sequence
is configured with the Wake-up (WAKE) configuration
option and can be disabled or set to 50 ms, 75 ms, or
100 ms of pulses of Te width.
FIRMWARE MODULES
The following files make up the KEELOQ transmitter
firmware:
- TX_16F636.asm: this file contains the main
loop routine as well as the wake-up,
debounce, read configuration, load transmit
buffer and transmit routines.
- Encrypt636.inc: this file runs the KEELOQ
encryption engine.
- TX_eeprom.inc: this file contains the
EEPROM data as specified on the EEPROM
data map.
- CounterCode.inc: Calculates the checksums
and confirms the validity of the counter.
CONCLUSION
This KEELOQ transmitter firmware has all the features
of a standard hardware encoder. What makes this
firmware implementation useful to the designer is that
it gives the designer the power and flexibility of
modifying the encoding and/or transmission formats
and parameters to suit their security system.
© 2009-2011 Microchip Technology Inc.
DS01259B-page 9
AN1259
ADDITIONAL INFORMATION
Microchip’s Secure Data Products are covered by
some or all of the following:
Code hopping encoder patents issued in European
countries and U.S.A.
Secure learning patents issued in European countries,
U.S.A. and R.S.A.
REVISION HISTORY
Revision B (June 2011)
• Added new section Additional Information
• Minor formatting and text changes were
incorporated throughout the document
DS01259B-page 10
© 2009-2011 Microchip Technology Inc.
Note the following details of the code protection feature on Microchip devices:
•
Microchip products meet the specification contained in their particular Microchip Data Sheet.
•
Microchip believes that its family of products is one of the most secure families of its kind on the market today, when used in the
intended manner and under normal conditions.
•
There are dishonest and possibly illegal methods used to breach the code protection feature. All of these methods, to our
knowledge, require using the Microchip products in a manner outside the operating specifications contained in Microchip’s Data
Sheets. Most likely, the person doing so is engaged in theft of intellectual property.
•
Microchip is willing to work with the customer who is concerned about the integrity of their code.
•
Neither Microchip nor any other semiconductor manufacturer can guarantee the security of their code. Code protection does not
mean that we are guaranteeing the product as “unbreakable.”
Code protection is constantly evolving. We at Microchip are committed to continuously improving the code protection features of our
products. Attempts to break Microchip’s code protection feature may be a violation of the Digital Millennium Copyright Act. If such acts
allow unauthorized access to your software or other copyrighted work, you may have a right to sue for relief under that Act.
Information contained in this publication regarding device
applications and the like is provided only for your convenience
and may be superseded by updates. It is your responsibility to
ensure that your application meets with your specifications.
MICROCHIP MAKES NO REPRESENTATIONS OR
WARRANTIES OF ANY KIND WHETHER EXPRESS OR
IMPLIED, WRITTEN OR ORAL, STATUTORY OR
OTHERWISE, RELATED TO THE INFORMATION,
INCLUDING BUT NOT LIMITED TO ITS CONDITION,
QUALITY, PERFORMANCE, MERCHANTABILITY OR
FITNESS FOR PURPOSE. Microchip disclaims all liability
arising from this information and its use. Use of Microchip
devices in life support and/or safety applications is entirely at
the buyer’s risk, and the buyer agrees to defend, indemnify and
hold harmless Microchip from any and all damages, claims,
suits, or expenses resulting from such use. No licenses are
conveyed, implicitly or otherwise, under any Microchip
intellectual property rights.
Trademarks
The Microchip name and logo, the Microchip logo, dsPIC,
KEELOQ, KEELOQ logo, MPLAB, PIC, PICmicro, PICSTART,
PIC32 logo, rfPIC and UNI/O are registered trademarks of
Microchip Technology Incorporated in the U.S.A. and other
countries.
FilterLab, Hampshire, HI-TECH C, Linear Active Thermistor,
MXDEV, MXLAB, SEEVAL and The Embedded Control
Solutions Company are registered trademarks of Microchip
Technology Incorporated in the U.S.A.
Analog-for-the-Digital Age, Application Maestro, chipKIT,
chipKIT logo, CodeGuard, dsPICDEM, dsPICDEM.net,
dsPICworks, dsSPEAK, ECAN, ECONOMONITOR,
FanSense, HI-TIDE, In-Circuit Serial Programming, ICSP,
Mindi, MiWi, MPASM, MPLAB Certified logo, MPLIB,
MPLINK, mTouch, Omniscient Code Generation, PICC,
PICC-18, PICDEM, PICDEM.net, PICkit, PICtail, REAL ICE,
rfLAB, Select Mode, Total Endurance, TSHARC,
UniWinDriver, WiperLock and ZENA are trademarks of
Microchip Technology Incorporated in the U.S.A. and other
countries.
SQTP is a service mark of Microchip Technology Incorporated
in the U.S.A.
All other trademarks mentioned herein are property of their
respective companies.
© 2009-2011, Microchip Technology Incorporated, Printed in
the U.S.A., All Rights Reserved.
Printed on recycled paper.
ISBN: 978-1-61341-266-4
Microchip received ISO/TS-16949:2002 certification for its worldwide
headquarters, design and wafer fabrication facilities in Chandler and
Tempe, Arizona; Gresham, Oregon and design centers in California
and India. The Company’s quality system processes and procedures
are for its PIC® MCUs and dsPIC® DSCs, KEELOQ® code hopping
devices, Serial EEPROMs, microperipherals, nonvolatile memory and
analog products. In addition, Microchip’s quality system for the design
and manufacture of development systems is ISO 9001:2000 certified.
© 2009-2011 Microchip Technology Inc.
DS01259B-page 11
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Fax: 886-2-2508-0102
China - Wuhan
Tel: 86-27-5980-5300
Fax: 86-27-5980-5118
Thailand - Bangkok
Tel: 66-2-694-1351
Fax: 66-2-694-1350
Spain - Madrid
Tel: 34-91-708-08-90
Fax: 34-91-708-08-91
UK - Wokingham
Tel: 44-118-921-5869
Fax: 44-118-921-5820
China - Xian
Tel: 86-29-8833-7252
Fax: 86-29-8833-7256
China - Xiamen
Tel: 86-592-2388138
Fax: 86-592-2388130
China - Zhuhai
Tel: 86-756-3210040
Fax: 86-756-3210049
DS01259B-page 12
Italy - Milan
Tel: 39-0331-742611
Fax: 39-0331-466781
Korea - Daegu
Tel: 82-53-744-4301
Fax: 82-53-744-4302
05/02/11
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