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. 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