├── LICENSE ├── README.md ├── decoder.ino └── helpers.ino /LICENSE: -------------------------------------------------------------------------------- 1 | GNU GENERAL PUBLIC LICENSE 2 | Version 2, June 1991 3 | 4 | Copyright (C) 1989, 1991 Free Software Foundation, Inc., 5 | 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA 6 | Everyone is permitted to copy and distribute verbatim copies 7 | of this license document, but changing it is not allowed. 8 | 9 | Preamble 10 | 11 | The licenses for most software are designed to take away your 12 | freedom to share and change it. By contrast, the GNU General Public 13 | License is intended to guarantee your freedom to share and change free 14 | software--to make sure the software is free for all its users. This 15 | General Public License applies to most of the Free Software 16 | Foundation's software and to any other program whose authors commit to 17 | using it. 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If this is what you want to do, use the GNU Lesser General 339 | Public License instead of this License. 340 | 341 | -------------------------------------------------------------------------------- /README.md: -------------------------------------------------------------------------------- 1 | # arduino-pocsag 2 | Arduino based POCSAG decoder using the frequency shift keying demodulator on Motorola pager RF boards. 3 | 4 | Tested successfully with up to 1200 baud POCSAG. 5 | 6 | More information to follow. 7 | -------------------------------------------------------------------------------- /decoder.ino: -------------------------------------------------------------------------------- 1 | /** 2 | * Decodes POCSAG data from the FSK demodulator output on the RF board of Motorola pagers. 3 | * Tested successfully with up to 1200 baud POCSAG 4 | 5 | * Copyright (C) 2013 Tom de Waha 6 | 7 | * This program is free software; you can redistribute it and/or modify 8 | * it under the terms of the GNU General Public License as published by 9 | * the Free Software Foundation; either version 2 of the License, or 10 | * (at your option) any later version. 11 | * This program is distributed in the hope that it will be useful, 12 | * but WITHOUT ANY WARRANTY; without even the implied warranty of 13 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 14 | * GNU General Public License for more details. 15 | * You should have received a copy of the GNU General Public License along 16 | * with this program; if not, write to the Free Software Foundation, Inc., 17 | * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA. 18 | **/ 19 | 20 | #include 21 | #define receiverPin 3 22 | #define triggerPin 6 23 | #define ledPin 13 24 | #define bitPeriod 833 25 | #define halfBitPeriod 416 26 | #define prmbWord 1431655765 27 | #define syncWord 2094142936 28 | #define idleWord 2055848343 29 | 30 | #define STATE_WAIT_FOR_PRMB 0 31 | #define STATE_WAIT_FOR_SYNC 1 32 | #define STATE_PROCESS_BATCH 2 33 | #define STATE_PROCESS_MESSAGE 3 34 | 35 | static const char *functions[4] = {"Function A", "Function B","Function C", "Function D"}; 36 | 37 | volatile unsigned long buffer = 0; 38 | volatile int bitcounter = 0; 39 | int state = 0; 40 | int wordcounter = 0; 41 | int framecounter = 0; 42 | int batchcounter = 0; 43 | 44 | unsigned long wordbuffer[81]; 45 | 46 | void setup() 47 | { 48 | pinMode(receiverPin, INPUT); 49 | pinMode(triggerPin, OUTPUT); 50 | disable_led(); 51 | disable_trigger(); 52 | start_flank(); 53 | Timer1.initialize(bitPeriod); 54 | } 55 | 56 | void loop() 57 | { 58 | switch(state) 59 | { 60 | case STATE_WAIT_FOR_PRMB: 61 | if(buffer==prmbWord) 62 | { 63 | state = STATE_WAIT_FOR_SYNC; 64 | } 65 | break; 66 | 67 | case STATE_WAIT_FOR_SYNC: 68 | if(buffer==syncWord) 69 | { 70 | bitcounter = 0; 71 | state = STATE_PROCESS_BATCH; 72 | } else { 73 | if(bitcounter > 540) // SYNC word did not appear, going back to idle mode 74 | { 75 | bitcounter = 0; 76 | if(batchcounter > 0) 77 | { 78 | state = STATE_PROCESS_MESSAGE; 79 | } else { 80 | state = STATE_WAIT_FOR_PRMB; 81 | } 82 | batchcounter = 0; 83 | } 84 | } 85 | break; 86 | 87 | case STATE_PROCESS_BATCH: 88 | if(bitcounter >= 32) 89 | { 90 | bitcounter = 0; 91 | wordbuffer[(batchcounter * 16)+(framecounter*2)+wordcounter] = buffer; 92 | wordcounter++; 93 | } 94 | 95 | if(wordcounter >= 2) 96 | { 97 | wordcounter = 0; 98 | framecounter++; 99 | } 100 | 101 | if(framecounter >= 8) 102 | { 103 | framecounter = 0; 104 | batchcounter++; 105 | state = STATE_WAIT_FOR_SYNC; 106 | } 107 | 108 | if(batchcounter >= 5) 109 | { 110 | batchcounter = 0; 111 | state = STATE_PROCESS_MESSAGE; 112 | } 113 | break; 114 | 115 | case STATE_PROCESS_MESSAGE: 116 | stop_flank(); 117 | stop_timer(); 118 | 119 | decode_wordbuffer(); 120 | 121 | memset(wordbuffer,0,sizeof(wordbuffer)); 122 | state = STATE_WAIT_FOR_PRMB; 123 | 124 | start_flank(); 125 | break; 126 | } 127 | } 128 | 129 | void decode_wordbuffer() 130 | { 131 | unsigned long address = 0; 132 | byte function = 0; 133 | char message[160]; 134 | memset(message,0,sizeof(message)); 135 | byte character = 0; 136 | int bcounter = 0; 137 | int ccounter = 0; 138 | boolean eot = false; 139 | 140 | for(int i=0;i<81;i++) 141 | { 142 | if(parity(wordbuffer[i]) == 1) continue; // Invalid Codeword 143 | if(wordbuffer[i] == idleWord) continue; // IDLE 144 | if(wordbuffer[i] == 0) continue; // Empty Codeword 145 | 146 | if(bitRead(wordbuffer[i], 31) == 0) // Found an Address 147 | { 148 | if(address == 0) 149 | { 150 | address = extract_address(i); 151 | function = extract_function(i); 152 | eot = false; 153 | } 154 | } else { 155 | if(address != 0 && ccounter < 160) 156 | { 157 | for(int c = 30; c > 10; c--) 158 | { 159 | bitWrite(character, bcounter, bitRead(wordbuffer[i], c)); 160 | bcounter++; 161 | if(bcounter >= 7) 162 | { 163 | if(character == 4) eot=true; 164 | bcounter = 0; 165 | if(eot==false) 166 | { 167 | message[ccounter] = character; 168 | ccounter++; 169 | } 170 | } 171 | } 172 | } 173 | } 174 | } 175 | if(address != 0) 176 | { 177 | print_message(address, function, message); 178 | } 179 | } 180 | 181 | void print_message(unsigned long address, byte function, char message[160]) 182 | { 183 | Serial.begin(115200); 184 | if(address<1000000) Serial.print("0"); 185 | Serial.print(address); 186 | Serial.print("\t"); 187 | Serial.print(functions[function]); 188 | Serial.print("\t"); 189 | Serial.println(message); 190 | Serial.end(); 191 | } 192 | 193 | unsigned long extract_address(int idx) 194 | { 195 | unsigned long address = 0; 196 | int pos = (idx - (idx/8) * 8)/2; 197 | for(int i = 1; i < 19; i++) 198 | { 199 | bitWrite(address, 21-i, bitRead(wordbuffer[idx], 31-i)); 200 | } 201 | bitWrite(address, 0, bitRead((pos), 0)); 202 | bitWrite(address, 1, bitRead((pos), 1)); 203 | bitWrite(address, 2, bitRead((pos), 2)); 204 | 205 | return address; 206 | } 207 | 208 | byte extract_function(int idx) 209 | { 210 | byte function = 0; 211 | bitWrite(function, 0, bitRead(wordbuffer[idx], 11)); 212 | bitWrite(function, 1, bitRead(wordbuffer[idx], 12)); 213 | return function; 214 | } 215 | 216 | void flank_isr() 217 | { 218 | delayMicroseconds(halfBitPeriod-20); 219 | start_timer(); 220 | } 221 | 222 | void timer_isr() 223 | { 224 | buffer = buffer << 1; 225 | bitWrite(buffer, 0, bitRead(PIND,3)); 226 | if(state > STATE_WAIT_FOR_PRMB) bitcounter++; 227 | } 228 | 229 | void start_timer() 230 | { 231 | Timer1.restart(); 232 | Timer1.attachInterrupt(timer_isr); 233 | } 234 | 235 | void stop_timer() 236 | { 237 | Timer1.detachInterrupt(); 238 | } 239 | 240 | void start_flank() 241 | { 242 | attachInterrupt(1, flank_isr, RISING); 243 | } 244 | 245 | void stop_flank() 246 | { 247 | detachInterrupt(1); 248 | } 249 | 250 | 251 | 252 | 253 | -------------------------------------------------------------------------------- /helpers.ino: -------------------------------------------------------------------------------- 1 | /** 2 | * Provides helper functions for the pocsag decoder 3 | * Copyright (C) 2013 Tom de Waha 4 | 5 | * This program is free software; you can redistribute it and/or modify 6 | * it under the terms of the GNU General Public License as published by 7 | * the Free Software Foundation; either version 2 of the License, or 8 | * (at your option) any later version. 9 | * This program is distributed in the hope that it will be useful, 10 | * but WITHOUT ANY WARRANTY; without even the implied warranty of 11 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 12 | * GNU General Public License for more details. 13 | * You should have received a copy of the GNU General Public License along 14 | * with this program; if not, write to the Free Software Foundation, Inc., 15 | * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA. 16 | **/ 17 | 18 | #define CLR(x,y) (x&=(~(1<> 16; 46 | x = x ^ x >> 8; 47 | x = x ^ x >> 4; 48 | x = x ^ x >> 2; 49 | x = x ^ x >> 1; 50 | return x & 1; 51 | } 52 | 53 | void trigger() 54 | { 55 | SET(PORTD, triggerPin); 56 | CLR(PORTD, triggerPin); 57 | } 58 | 59 | void enable_trigger() 60 | { 61 | SET(PORTD, triggerPin); 62 | } 63 | 64 | void disable_trigger() 65 | { 66 | CLR(PORTD, triggerPin); 67 | } 68 | 69 | void enable_led() 70 | { 71 | SET(PORTD, ledPin); 72 | } 73 | 74 | void disable_led() 75 | { 76 | CLR(PORTD, ledPin); 77 | } 78 | --------------------------------------------------------------------------------