Rev 4 | Details | Compare with Previous | Last modification | View Log | RSS feed
| Rev | Author | Line No. | Line |
|---|---|---|---|
| 1 | mjames | 1 | /* |
| 2 | * nmea.c |
||
| 3 | * |
||
| 4 | * Created on: 6 Sep 2020 |
||
| 5 | * Author: mike |
||
| 6 | */ |
||
| 7 | |||
| 8 | #include <math.h> |
||
| 9 | #include <stdint.h> |
||
| 10 | #include <stdlib.h> |
||
| 11 | #include <memory.h> |
||
| 12 | |||
| 13 | #include "libNMEA/nmea.h" |
||
| 14 | |||
| 15 | #include "libSerial/serial.h" |
||
| 16 | |||
| 17 | char linebuff[80]; |
||
| 18 | unsigned linePos = 0; |
||
| 19 | |||
| 2 | mjames | 20 | nmeaCallback rmcCallback = NULL; |
| 21 | |||
| 1 | mjames | 22 | typedef enum |
| 23 | { |
||
| 3 | mjames | 24 | SEARCH, |
| 25 | READING |
||
| 1 | mjames | 26 | } NmeaState_t; |
| 27 | |||
| 28 | NmeaState_t lineState = SEARCH; |
||
| 29 | |||
| 30 | static bool |
||
| 3 | mjames | 31 | decodePacket(char *linebuff, int linePos, Location *loc); |
| 1 | mjames | 32 | |
| 3 | mjames | 33 | bool updateLocation(Location *loc, usart_ctl *uc) |
| 1 | mjames | 34 | { |
| 5 | mjames | 35 | while(PollSerial(uc)) |
| 4 | mjames | 36 | { |
| 37 | char c = GetCharSerial(uc); |
||
| 38 | switch (lineState) |
||
| 3 | mjames | 39 | { |
| 4 | mjames | 40 | case SEARCH: |
| 41 | if (c != '$') |
||
| 42 | break; |
||
| 43 | lineState = READING; |
||
| 44 | linePos = 0; |
||
| 45 | case READING: |
||
| 46 | if (c == '\r') |
||
| 3 | mjames | 47 | { |
| 4 | mjames | 48 | // log the actual time of reading |
| 1 | mjames | 49 | |
| 4 | mjames | 50 | // handle the packet |
| 5 | mjames | 51 | decodePacket(linebuff, linePos, loc); |
| 1 | mjames | 52 | |
| 4 | mjames | 53 | lineState = SEARCH; |
| 5 | mjames | 54 | break; |
| 3 | mjames | 55 | } |
| 4 | mjames | 56 | // if the line buffer is not full, place character in buffer |
| 57 | if (linePos < sizeof(linebuff)) |
||
| 58 | linebuff[linePos++] = c; |
||
| 59 | else |
||
| 60 | { |
||
| 61 | lineState = SEARCH; |
||
| 62 | // search for the $ in any unread string |
||
| 63 | for (int i = 1; i < linePos; i++) |
||
| 64 | if (linebuff[i] == '$') |
||
| 65 | { |
||
| 66 | memcpy(linebuff, linebuff + i, linePos - i); |
||
| 67 | linePos = 1; |
||
| 68 | linebuff[linePos++] = c; |
||
| 69 | lineState = READING; |
||
| 70 | } |
||
| 71 | |||
| 72 | if (lineState == SEARCH) |
||
| 73 | linePos = 0; |
||
| 74 | } |
||
| 75 | break; |
||
| 76 | } |
||
| 1 | mjames | 77 | } |
| 3 | mjames | 78 | return false; |
| 1 | mjames | 79 | } |
| 80 | |||
| 81 | static int8_t |
||
| 3 | mjames | 82 | decodeDec(char c) |
| 1 | mjames | 83 | { |
| 3 | mjames | 84 | if (c > '9' && c < '0') |
| 85 | return -1; |
||
| 86 | return c - '0'; |
||
| 1 | mjames | 87 | } |
| 88 | |||
| 89 | static uint8_t |
||
| 3 | mjames | 90 | decodeHex(char c) |
| 1 | mjames | 91 | { |
| 3 | mjames | 92 | int8_t v = decodeDec(c); |
| 93 | if (v >= 0) |
||
| 94 | return v; |
||
| 95 | c = tolower(c); |
||
| 96 | if (c >= 'a' && c <= 'f') |
||
| 97 | return c - 'a' + 10; |
||
| 98 | return 0; |
||
| 1 | mjames | 99 | } |
| 100 | |||
| 101 | // lat/long decoder |
||
| 102 | static float |
||
| 3 | mjames | 103 | decodeLL(char *ptr, int msDigitWeight) |
| 1 | mjames | 104 | { |
| 3 | mjames | 105 | float digitWeight = msDigitWeight; |
| 106 | float result = 0; |
||
| 107 | int i = 0; |
||
| 108 | while (1) |
||
| 1 | mjames | 109 | { |
| 3 | mjames | 110 | char c = ptr[i++]; |
| 111 | if (c == '.') |
||
| 112 | continue; |
||
| 113 | int8_t v = decodeDec(c); |
||
| 114 | if (v > 0) |
||
| 115 | { |
||
| 116 | result += digitWeight * v; |
||
| 117 | if (fabs(digitWeight - 1) < 0.01) |
||
| 118 | digitWeight = 1 / 6.0; |
||
| 119 | else |
||
| 120 | digitWeight = digitWeight / 10; |
||
| 1 | mjames | 121 | |
| 3 | mjames | 122 | continue; |
| 123 | } |
||
| 124 | break; |
||
| 1 | mjames | 125 | } |
| 126 | |||
| 3 | mjames | 127 | return result; |
| 1 | mjames | 128 | } |
| 129 | |||
| 130 | static float |
||
| 3 | mjames | 131 | decodeFP(char *ptr) |
| 1 | mjames | 132 | { |
| 3 | mjames | 133 | return strtof(ptr, NULL); |
| 1 | mjames | 134 | } |
| 135 | |||
| 136 | static int |
||
| 3 | mjames | 137 | decodeDecimal(char *ptr) |
| 1 | mjames | 138 | { |
| 3 | mjames | 139 | int i; |
| 140 | int res = 0; |
||
| 141 | int const width = 2; |
||
| 142 | for (i = 0; i < width; i++) |
||
| 143 | { |
||
| 144 | int8_t v = decodeDec(*ptr++); |
||
| 145 | if (v < 0) |
||
| 146 | return 0; |
||
| 147 | res *= 10; |
||
| 148 | res += v; |
||
| 149 | } |
||
| 150 | return res; |
||
| 1 | mjames | 151 | } |
| 152 | |||
| 3 | mjames | 153 | bool decodePacket(char *linebuff, int linePos, Location *loc) |
| 1 | mjames | 154 | { |
| 2 | mjames | 155 | |
| 3 | mjames | 156 | uint8_t checksum = 0; |
| 157 | for (int i = 1; i < linePos - 3; i++) |
||
| 158 | checksum ^= linebuff[i]; |
||
| 159 | uint8_t givenSum = (decodeHex(linebuff[linePos - 2]) << 4) + decodeHex(linebuff[linePos - 1]); |
||
| 160 | if (givenSum != checksum) |
||
| 161 | return false; |
||
| 1 | mjames | 162 | |
| 3 | mjames | 163 | char *fieldPos[20]; |
| 164 | int fieldCnt = 0; |
||
| 165 | // split fields |
||
| 166 | for (int i = 6; i < linePos - 3; i++) |
||
| 1 | mjames | 167 | { |
| 3 | mjames | 168 | if (linebuff[i] == ',') |
| 169 | { |
||
| 170 | fieldPos[fieldCnt++] = linebuff + i + 1; |
||
| 171 | } |
||
| 1 | mjames | 172 | } |
| 173 | |||
| 3 | mjames | 174 | // decode RMC |
| 175 | if (linebuff[3] == 'R' && linebuff[4] == 'M' && linebuff[5] == 'C') |
||
| 1 | mjames | 176 | |
| 3 | mjames | 177 | { |
| 1 | mjames | 178 | |
| 3 | mjames | 179 | // decode the fields |
| 180 | loc->valid = *fieldPos[1]; |
||
| 181 | if (loc->valid == 'A') |
||
| 182 | { |
||
| 183 | memcpy(loc->time, fieldPos[0], 6); |
||
| 184 | loc->lat = decodeLL(fieldPos[2], 10); |
||
| 185 | loc->ns = *fieldPos[3]; |
||
| 186 | loc->lon = decodeLL(fieldPos[4], 100); |
||
| 187 | loc->ew = *fieldPos[5]; |
||
| 188 | loc->speed = decodeFP(fieldPos[6]); |
||
| 189 | loc->heading = decodeFP(fieldPos[7]); |
||
| 190 | memcpy(loc->date, fieldPos[1], 6); |
||
| 2 | mjames | 191 | |
| 3 | mjames | 192 | loc->tv.tm_sec = decodeDecimal(&loc->time[4]); |
| 193 | loc->tv.tm_min = decodeDecimal(&loc->time[2]); |
||
| 194 | loc->tv.tm_hour = decodeDecimal(&loc->time[0]); |
||
| 2 | mjames | 195 | |
| 3 | mjames | 196 | loc->tv.tm_mday = decodeDecimal(&loc->date[0]); |
| 197 | loc->tv.tm_mon = decodeDecimal(&loc->date[2]) - 1; |
||
| 198 | loc->tv.tm_year = decodeDecimal(&loc->date[4]) + 100; // |
||
| 1 | mjames | 199 | |
| 3 | mjames | 200 | loc->tv.tm_isdst = 0; |
| 201 | loc->utc = mktime(&loc->tv); |
||
| 1 | mjames | 202 | |
| 3 | mjames | 203 | loc->good = true; |
| 204 | } |
||
| 205 | if (rmcCallback) |
||
| 206 | { |
||
| 207 | linebuff[linePos++] = '\r'; |
||
| 208 | linebuff[linePos++] = '\n'; |
||
| 209 | linebuff[linePos++] = 0; |
||
| 4 | mjames | 210 | |
| 3 | mjames | 211 | rmcCallback((uint8_t *)linebuff, linePos); |
| 212 | } |
||
| 1 | mjames | 213 | } |
| 2 | mjames | 214 | |
| 3 | mjames | 215 | return true; |
| 1 | mjames | 216 | } |
| 2 | mjames | 217 | |
| 3 | mjames | 218 | void setRmcCallback(nmeaCallback callback) |
| 2 | mjames | 219 | { |
| 3 | mjames | 220 | rmcCallback = callback; |
| 2 | mjames | 221 | } |