1 | // *******************************************************************************
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2 |
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3 | // Routine to synchronize bit periods in a Manchester encoded stream
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4 |
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5 | // Always sync to rising edge
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6 |
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7 | // ******************************************************************************/
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8 |
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9 | unsigned char U2270_Manchester2TSync(void)
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10 |
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11 | {
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12 |
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13 | unsigned char level;
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14 |
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15 | RFIDTimerFlag = 0; // Clear Timer Flag
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16 |
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17 | while(!RFIDTimerFlag); // Wait for next edge
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18 |
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19 |
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20 |
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21 | level = (PIND & 0x10); // Check logic level of data line
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22 |
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23 | level = (PIND & 0x10); // Redundancy check
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24 |
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25 |
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26 |
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27 | // Make sure edge time is a Manchester long time //
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28 |
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29 | if(RdTime > U2270_LongL && RdTime < U2270_LongH && level == 0 )
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30 |
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31 | {
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32 |
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33 | PORTF &= ~0x02;
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34 |
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35 | Timer_delay_us(2);
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36 |
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37 | PORTF |= 0x02;
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38 |
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39 | return 1; // Logic value of current bit
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40 |
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41 | }
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42 |
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43 | else return SeqTermErr; // Edge time and level error
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44 |
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45 | }
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46 |
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47 |
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48 |
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49 | // *******************************************************************************
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50 |
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51 | // Routine to decode a Manchester bit
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52 |
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53 | // Pass in the previous bit logic value
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54 |
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55 | // ******************************************************************************/
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56 |
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57 | unsigned char U2270_ManchesterDecode(unsigned char cBit)
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58 |
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59 | {
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60 |
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61 | RFIDTimerFlag = 0; // Clear Timer Flag
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62 |
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63 | while(!RFIDTimerFlag); // Wait for next edge
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64 |
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65 |
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66 |
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67 | // Check edge time and determine next Logic value //
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68 |
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69 | if(RdTime > U2270_LongL && RdTime < U2270_LongH && cBit == 1){return 0;}
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70 |
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71 | else if(RdTime > U2270_LongL && RdTime < U2270_LongH && cBit == 0){return 1;}
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72 |
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73 | else if(RdTime > U2270_ShortL && RdTime < U2270_ShortH) // Next edge time is short
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74 |
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75 | {
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76 |
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77 | RFIDTimerFlag = 0; // Clear Timer flag
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78 |
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79 | while(!RFIDTimerFlag); // Wait for next edge
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80 |
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81 | if(RdTime > U2270_ShortL && RdTime < U2270_ShortH && cBit == 1){return 1;}
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82 |
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83 | else if(RdTime > U2270_ShortL && RdTime < U2270_ShortH && cBit == 0){return 0;}
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84 |
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85 | else
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86 |
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87 | {
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88 |
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89 | //PORTF &= ~0x02;
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90 |
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91 | //PORTF |= 0x02;
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92 |
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93 | return BitErr; // Un-paired short time between two long times
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94 |
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95 | }
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96 |
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97 | }
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98 |
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99 | else {return BitErr;} // Edge time outside limits
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100 |
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101 | }
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102 |
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103 |
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104 |
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105 | // *******************************************************************************
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106 |
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107 | // Routine to decode a BiPhase bit
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108 |
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109 | // ******************************************************************************/
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110 |
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111 | unsigned char U2270_BiPhaseDecode(void)
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112 |
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113 | {
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114 |
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115 | RFIDTimerFlag = 0; // Clear Timer Flag
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116 |
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117 | while(!RFIDTimerFlag); // Wait for next edge
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118 |
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119 |
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120 |
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121 | // Check edge time and determine next Logic value //
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122 |
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123 | if(RdTime > U2270_LongL && RdTime < U2270_LongH){return 1;}
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124 |
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125 | else if(RdTime > U2270_ShortL && RdTime < U2270_ShortH) // Next edge time is short
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126 |
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127 | {
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128 |
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129 | RFIDTimerFlag = 0; // Clear Timer flag
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130 |
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131 | while(!RFIDTimerFlag); // Wait for next edge
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132 |
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133 | if(RdTime > U2270_ShortL && RdTime < U2270_ShortH){return 0;}
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134 |
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135 | else
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136 |
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137 | {
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138 |
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139 | return BitErr; // Un-paired short time between two long times
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140 |
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141 | }
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142 |
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143 | }
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144 |
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145 | else {return BitErr;} // Edge time outside limits
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146 |
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147 | }
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148 |
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149 |
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150 |
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151 | // *******************************************************************************
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152 |
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153 | // Routine to find Decode the Dual Pattern Bit
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154 |
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155 | // ******************************************************************************/
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156 |
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157 | unsigned char U2270_DualPatternDecode(void)
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158 |
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159 | {
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160 |
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161 | RFIDTimerFlag = 0; // Clear Timer Flag
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162 |
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163 | while(!RFIDTimerFlag); // Wait for next edge
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164 |
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165 |
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166 |
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167 | // Check edge time and determine next Logic value //
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168 |
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169 | if(RdTime > U2270_ShortL-30 && RdTime < U2270_ShortH+20)
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170 |
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171 | {
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172 |
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173 | RFIDTimerFlag = 0; // Clear Timer flag
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174 |
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175 | while(!RFIDTimerFlag); // Wait for next edge
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176 |
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177 | if(RdTime > U2270_ShortL-20 && RdTime < U2270_ShortH+20){return 1;}
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178 |
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179 | else {return BitErr;} // Un-paired short time between two long times
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180 |
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181 | }
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182 |
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183 | else if(RdTime > U2270_LongL && RdTime < U2270_LongH+30)
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184 |
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185 | {
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186 |
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187 | RFIDTimerFlag = 0; // Clear Timer flag
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188 |
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189 | while(!RFIDTimerFlag); // Wait for next edge
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190 |
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191 | return 0;
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192 |
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193 | }
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194 |
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195 | else {return BitErr;} // Edge time outside limits
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196 |
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197 | }
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