1 | /******************************************************************************/
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2 | extern void MsgHandler(unsigned char newchar)
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3 | /*******************************************************************************
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4 | * ABSTRACT: Processes the characters coming in from USART. In this case,
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5 | * this is the port connected to the gps receiver.
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6 | *
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7 | * INPUT: newchar Next character from the serial port.
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8 | * OUTPUT: None
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9 | * RETURN: None
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10 | */
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11 | {
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12 | static unsigned char commas; // Number of commas for far in sentence
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13 | static unsigned char index; // Individual array index
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14 |
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15 | if (newchar == 0) // A NULL character resets GPS decoding
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16 | {
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17 | commas = 25; // Set to an outrageous value
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18 | sentence_type = FALSE; // Clear local parse variable
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19 | return;
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20 | }
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21 |
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22 | if (newchar == '$') // Start of Sentence character, reset
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23 | {
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24 | commas = 0; // No commas detected in sentence for far
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25 | sentence_type = FALSE; // Clear local parse variable
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26 | return;
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27 | }
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28 |
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29 | if (newchar == ',') // If there is a comma
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30 | {
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31 | commas += 1; // Increment the comma count
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32 | index = 0; // And reset the field index
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33 | return;
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34 | }
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35 |
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36 | if (commas == 0)
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37 | {
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38 | switch(newchar)
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39 | {
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40 | case ('C'): // Only the GPRMC sentence contains a "C"
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41 | sentence_type = GPRMC; // Set local parse variable
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42 | break;
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43 | case ('S'): // Take note if sentence contains an "S"
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44 | sentence_type = 'S'; // ...because we don't want to parse it
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45 | break;
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46 | case ('A'): // The GPGGA sentence ID contains "A"
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47 | if (sentence_type != 'S') // As does GPGSA, which we will ignore
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48 | sentence_type = GPGGA; // Set local parse variable
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49 | break;
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50 | }
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51 |
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52 | return;
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53 | }
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54 |
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55 | if (sentence_type == GPGGA) // GPGGA sentence decode initiated
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56 | {
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57 | switch (commas)
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58 | {
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59 | case (1): // Time field, grab characters
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60 | Time_Temp[index++] = newchar;
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61 | return;
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62 | case (2): // Latitude field, grab chars
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63 | Latitude_Temp[index++] = newchar;
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64 | return;
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65 | case (3):
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66 | Northsouth_Temp = newchar;
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67 | return;
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68 | case (4): // Longitude field, grab chars
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69 | Longitude_Temp[index++] = newchar;
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70 | return;
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71 | case (5):
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72 | Eastwest_Temp = newchar;
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73 | return;
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74 | case (7): // Satellite field, grab chars
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75 | Satellites_Temp[index++] = newchar;
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76 | return;
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77 | case (9): // Altitude field, grab chars
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78 | Altitude_Temp[index++] = newchar;
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79 | return;
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80 | }
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81 |
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82 | return;
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83 | } // end if (sentence_type == GPGGA)
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84 |
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85 | if (sentence_type == GPRMC) // GPGGA sentence decode initiated
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86 | {
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87 | switch (commas)
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88 | {
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89 | case (7): // Speed field, grab characters
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90 | Speed_Temp[index++] = newchar;
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91 | return;
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92 | case (8): // Course field, grab characters
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93 | Course_Temp[index++] = newchar;
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94 | return;
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95 | }
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96 |
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97 | return;
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98 | } // end if (sentence_type == GPRMC)
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99 |
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100 | return;
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101 |
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102 | } // End MsgHandler(unsigned char newchar)
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