Line data    Source code

       1             : /*
       2             :    This program is free software: you can redistribute it and/or modify
       3             :    it under the terms of the GNU General Public License as published by
       4             :    the Free Software Foundation, either version 3 of the License, or
       5             :    (at your option) any later version.
       6             : 
       7             :    This program is distributed in the hope that it will be useful,
       8             :    but WITHOUT ANY WARRANTY; without even the implied warranty of
       9             :    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
      10             :    GNU General Public License for more details.
      11             : 
      12             :    You should have received a copy of the GNU General Public License
      13             :    along with this program.  If not, see <http://www.gnu.org/licenses/>.
      14             :  */
      15             : 
      16             : #include "AP_RangeFinder_TeraRanger_Serial.h"
      17             : 
      18             : #if AP_RANGEFINDER_TERARANGER_SERIAL_ENABLED
      19             : 
      20             : 
      21             : #include <AP_HAL/utility/sparse-endian.h>
      22             : #include <AP_Math/AP_Math.h>
      23             : #include <ctype.h>
      24             : 
      25             : #define FRAME_HEADER 0x54
      26             : #define FRAME_LENGTH 5
      27             : #define DIST_MAX 30.00
      28             : #define OUT_OF_RANGE_ADD 10.00
      29             : #define STATUS_MASK 0x1F
      30             : #define DISTANCE_ERROR 0x0001
      31             : 
      32             : // format of serial packets received from rangefinder
      33             : //
      34             : // Data Bit             Definition      Description
      35             : // ------------------------------------------------
      36             : // byte 0               Frame header    0x54
      37             : // byte 1               DIST_H          Distance (in mm) high 8 bits
      38             : // byte 2               DIST_L          Distance (in mm) low 8 bits
      39             : // byte 3               STATUS          Status,Strengh,OverTemp
      40             : // byte 4               CRC8            packet CRC
      41             : 
      42             : // distance returned in reading_m, set to true if sensor reports a good reading
      43        1343 : bool AP_RangeFinder_TeraRanger_Serial::get_reading(float &reading_m)
      44             : {
      45        1343 :     if (uart == nullptr) {
      46           0 :         return false;
      47             :     }
      48             : 
      49        1343 :     float sum_mm = 0;
      50        1343 :     uint16_t count = 0;
      51        1343 :     uint16_t bad_read = 0;
      52             : 
      53             :     // read any available lines from the lidar
      54        3068 :     for (auto i=0; i<8192; i++) {
      55             :         uint8_t c;
      56        3068 :         if (!uart->read(c)) {
      57        1343 :             break;
      58             :         }
      59             :         // if buffer is empty and this byte is 0x57, add to buffer
      60        1725 :         if (linebuf_len == 0) {
      61         345 :             if (c == FRAME_HEADER) {
      62         345 :                 linebuf[linebuf_len++] = c;
      63             :             }
      64             :         // buffer is not empty, add byte to buffer
      65             :         } else {
      66             :             // add character to buffer
      67        1380 :             linebuf[linebuf_len++] = c;
      68             :             // if buffer now has 5 items try to decode it
      69        1380 :             if (linebuf_len == FRAME_LENGTH) {
      70             :                 // calculate CRC8 (tbd)
      71         345 :                 uint8_t crc = 0;
      72         345 :                 crc =crc_crc8(linebuf,FRAME_LENGTH-1);
      73             :                 // if crc matches, extract contents
      74         345 :                 if (crc == linebuf[FRAME_LENGTH-1]) {
      75             :                     // calculate distance
      76         345 :                     uint16_t dist = ((uint16_t)linebuf[1] << 8) | linebuf[2];
      77         345 :                     if (dist >= DIST_MAX *1000) {
      78             :                         // this reading is out of range and a bad read
      79           0 :                         bad_read++;
      80             :                     } else {
      81             :                         // check if reading is good, no errors, no overtemp, reading is not the special case of 1mm
      82         345 :                         if ((STATUS_MASK & linebuf[3]) == 0 && (dist != DISTANCE_ERROR)) {
      83             :                             // add distance to sum
      84         345 :                             sum_mm += dist;
      85         345 :                             count++;
      86             :                         } else {
      87             :                             // this reading is bad
      88           0 :                             bad_read++;
      89             :                         }
      90             :                     }
      91             :                 }
      92             :                 // clear buffer
      93         345 :                 linebuf_len = 0;
      94             :             }
      95             :         }
      96             :     }
      97             : 
      98        1343 :     if (count > 0) {
      99             :         // return average distance of readings since last update
     100         338 :         reading_m = (sum_mm * 0.001f) / count;
     101         338 :         return true;
     102             :     }
     103             : 
     104        1005 :     if (bad_read > 0) {
     105             :         // if a bad read has occurred this update overwrite return with larger of
     106             :         // driver defined maximum range for the model and user defined max range + 1m
     107           0 :         reading_m = MAX(DIST_MAX, max_distance() + OUT_OF_RANGE_ADD);
     108           0 :         return true;
     109             :     }
     110             : 
     111             :     // no readings so return false
     112        1005 :     return false;
     113             : }
     114             : 
     115             : #endif // AP_RANGEFINDER_TERARANGER_SERIAL_ENABLED