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_NoopLoop.h"
      17             : 
      18             : #if AP_RANGEFINDER_NOOPLOOP_ENABLED
      19             : 
      20             : #include <AP_HAL/AP_HAL.h>
      21             : #include <AP_HAL/utility/sparse-endian.h>
      22             : 
      23             : #include <ctype.h>
      24             : 
      25             : extern const AP_HAL::HAL& hal;
      26             : 
      27             : #define NOOPLOOP_FRAME_HEADER 0x57
      28             : #define NOOPLOOP_FRAME_HEADER_1 0x00
      29             : #define NOOPLOOP_FRAME_LENGTH 16
      30             : #define NOOPLOOP_DIST_MAX_MM 8000
      31             : 
      32             : // format of serial packets received from NoopLoop TOF Sense P and F lidar
      33             : //
      34             : // Data Bit             Definition             Description
      35             : // -----------------------------------------------------------------------
      36             : // byte 0               Frame header           0x57
      37             : // byte 1               Function Mark          0x00
      38             : // byte 2               (Reserved)
      39             : // byte 3               Id                     id
      40             : // byte 4-7             System time            System time in ms
      41             : // byte 8-10            Distance*1000
      42             : // byte 11              Status                 Strength high 8 bits
      43             : // byte 12-13           Signal Strength
      44             : // byte 14              (Reserved)
      45             : // byte 15              Checksum
      46             : 
      47             : // distance returned in reading_m
      48        1361 : bool AP_RangeFinder_NoopLoop::get_reading(float &reading_m)
      49             : {
      50        1361 :     if (uart == nullptr) {
      51           0 :         return false;
      52             :     }
      53             : 
      54             :     // read any available lines from the lidar
      55        1361 :     uint32_t nbytes = uart->available();
      56        6491 :     while (nbytes-- > 0) {
      57             :         uint8_t c;
      58        5472 :         if (!uart->read(c)) {
      59           0 :             break;
      60             :         }
      61             :         // if buffer is empty and this byte is 0x57, add to buffer
      62        5472 :         if (linebuf_len == 0) {
      63         342 :             if (c == NOOPLOOP_FRAME_HEADER) {
      64         342 :                 linebuf[linebuf_len++] = c;
      65             :             }
      66        5130 :         } else if (linebuf_len == 1) {
      67             :             // if buffer has 1 element and this byte is 0x00, add it to buffer
      68             :             // if not clear the buffer
      69         342 :             if (c == NOOPLOOP_FRAME_HEADER_1) {
      70         342 :                 linebuf[linebuf_len++] = c;
      71             :             } else {
      72           0 :                 linebuf_len = 0;
      73             :             }
      74             :         } else {
      75             :             // add character to buffer
      76        4788 :             linebuf[linebuf_len++] = c;
      77             :             // if buffer now has 16 items try to decode it
      78        4788 :             if (linebuf_len == NOOPLOOP_FRAME_LENGTH) {
      79             :                 // calculate checksum
      80         342 :                 uint8_t checksum = 0;
      81        5472 :                 for (uint8_t i=0; i<NOOPLOOP_FRAME_LENGTH-1; i++) {
      82        5130 :                     checksum += linebuf[i];
      83             :                 }
      84             :                 // if checksum matches extract contents
      85         342 :                 if (checksum == linebuf[NOOPLOOP_FRAME_LENGTH-1]) {
      86             :                     // calculate distance
      87         342 :                     const int32_t dist = (int32_t)(linebuf[8] << 8 | linebuf[9] << 16 | linebuf[10] << 24) / 256;
      88         342 :                     const uint8_t valid = (linebuf[11]);
      89         342 :                     if (dist > 0 && reading_m < NOOPLOOP_DIST_MAX_MM && valid < 255) {
      90         342 :                         reading_m = dist * 0.001f;
      91         342 :                         linebuf_len = 0;
      92         342 :                         uart->discard_input();
      93         342 :                         return true;
      94             :                     }
      95             :                 }
      96             :                 // clear buffer
      97           0 :                 linebuf_len = 0;
      98           0 :                 uart->discard_input();
      99             :             }
     100             :         }
     101             :     }
     102             : 
     103             :     // no readings so return false
     104        1019 :     return false;
     105             : }
     106             : 
     107             : #endif  // AP_RANGEFINDER_NOOPLOOP_ENABLED