Added parsing function. Everything works OK.

TODO:
- Clean up the code
- Add uORB publishing messages

Signed-off-by: Claudio Micheli <claudio@auterion.com>

src/drivers/distance_sensor/airlango/isl2950.cpp

@@ -362,23 +362,53 @@ ISL2950::collect()
   perf_begin(_sample_perf);
 
   /* clear buffer if last read was too long ago */
-  //int64_t read_elapsed = hrt_elapsed_time(&_last_read);
+  int64_t read_elapsed = hrt_elapsed_time(&_last_read);
 
   // ----------------------- LANBAO SPECIFIC ---------------------------
-  //printf("enter ISL2950::collect() - reads from serial");
-    uint8_t buffer[50];
-    int bytes_available = 0;
-  //  int bytes_processed = 0;
-    int bytes_read = 0;
-  //  bool full_frame;
-bytes_read = bytes_read;
 
-    bytes_read = ::read(_fd, buffer + bytes_available, 50 - bytes_available);
-    printf("read() returns %02X %02X %02X %02X \n", buffer[0], buffer[1],buffer[2],buffer[3] );
+  uint8_t buffer[50];
+  int bytes_available = 0;
+  int bytes_processed = 0;
+  int bytes_read = 0;
+  bool full_frame;
+  int distance_mm = -1.0f;
+
+  bytes_read = ::read(_fd, buffer + bytes_available, 50 - bytes_available);
+  //printf("read() returns %02X %02X %02X %02X \n", buffer[0], buffer[1],buffer[2],buffer[3] );
 
 
   //--------------------------------------------------------------------
+  if (bytes_read < 0) {
+  		PX4_ERR("isl2950 - read() error: %d \n", bytes_read);
+  		perf_count(_comms_errors);
+  		perf_end(_sample_perf);
+
+  		/* only throw an error if we time out */
+  		if (read_elapsed > (_conversion_interval * 2)) {
+  			return bytes_read;
+
+  		} else {
+  			return -EAGAIN;
+  		}
+
+  } else if (bytes_read == 0) {
+  	return -EAGAIN;                         // SF0X drivers
+                                       // LANBAO driver
+  	}
+
+  bytes_available += bytes_read;
+
+  // parse the buffer data
+    full_frame = false;
+    bytes_processed = isl2950_parser(buffer, bytes_available, &full_frame,&distance_mm);
+    bytes_processed = bytes_processed;
+  //printf("isl2950_parser() processed %d bytes, full_frame %d \n", bytes_processed, full_frame);
+  if (full_frame) {
+    printf("Measured Distance %d \n",distance_mm*100);
+  }
+
 
+// ---------------------------- END EDIT
 	_last_read = hrt_absolute_time();
 	ret = OK;
 

src/drivers/distance_sensor/airlango/isl2950_parser.cpp

@@ -40,16 +40,164 @@
 #include "isl2950_parser.h"
 #include <string.h>
 #include <stdlib.h>
+#include <stdio.h>
 
 #include "isl2950_parser.h"
 #include <string.h>
 #include <stdlib.h>
 
+typedef unsigned char UCHAR;
+typedef unsigned short USHORT;
 
-int isl2950_parser(char c, char *parserbuf, unsigned *parserbuf_index, enum ISL2950_PARSE_STATE *state, float *dist)
+// Note : No clue what those static variables are
+static const UCHAR aucCRCHi[] = {
+  0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41,
+  0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40,
+  0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41,
+  0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41,
+  0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41,
+  0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40,
+  0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40,
+  0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40,
+  0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41,
+  0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40,
+  0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41,
+  0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41,
+  0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41,
+  0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41,
+  0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41,
+  0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41,
+  0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41,
+  0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40,
+  0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41,
+  0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41,
+  0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41,
+  0x00, 0xC1, 0x81, 0x40
+};
+
+static const UCHAR aucCRCLo[] = {
+  0x00, 0xC0, 0xC1, 0x01, 0xC3, 0x03, 0x02, 0xC2, 0xC6, 0x06, 0x07, 0xC7,
+  0x05, 0xC5, 0xC4, 0x04, 0xCC, 0x0C, 0x0D, 0xCD, 0x0F, 0xCF, 0xCE, 0x0E,
+  0x0A, 0xCA, 0xCB, 0x0B, 0xC9, 0x09, 0x08, 0xC8, 0xD8, 0x18, 0x19, 0xD9,
+  0x1B, 0xDB, 0xDA, 0x1A, 0x1E, 0xDE, 0xDF, 0x1F, 0xDD, 0x1D, 0x1C, 0xDC,
+  0x14, 0xD4, 0xD5, 0x15, 0xD7, 0x17, 0x16, 0xD6, 0xD2, 0x12, 0x13, 0xD3,
+  0x11, 0xD1, 0xD0, 0x10, 0xF0, 0x30, 0x31, 0xF1, 0x33, 0xF3, 0xF2, 0x32,
+  0x36, 0xF6, 0xF7, 0x37, 0xF5, 0x35, 0x34, 0xF4, 0x3C, 0xFC, 0xFD, 0x3D,
+  0xFF, 0x3F, 0x3E, 0xFE, 0xFA, 0x3A, 0x3B, 0xFB, 0x39, 0xF9, 0xF8, 0x38,
+  0x28, 0xE8, 0xE9, 0x29, 0xEB, 0x2B, 0x2A, 0xEA, 0xEE, 0x2E, 0x2F, 0xEF,
+  0x2D, 0xED, 0xEC, 0x2C, 0xE4, 0x24, 0x25, 0xE5, 0x27, 0xE7, 0xE6, 0x26,
+  0x22, 0xE2, 0xE3, 0x23, 0xE1, 0x21, 0x20, 0xE0, 0xA0, 0x60, 0x61, 0xA1,
+  0x63, 0xA3, 0xA2, 0x62, 0x66, 0xA6, 0xA7, 0x67, 0xA5, 0x65, 0x64, 0xA4,
+  0x6C, 0xAC, 0xAD, 0x6D, 0xAF, 0x6F, 0x6E, 0xAE, 0xAA, 0x6A, 0x6B, 0xAB,
+  0x69, 0xA9, 0xA8, 0x68, 0x78, 0xB8, 0xB9, 0x79, 0xBB, 0x7B, 0x7A, 0xBA,
+  0xBE, 0x7E, 0x7F, 0xBF, 0x7D, 0xBD, 0xBC, 0x7C, 0xB4, 0x74, 0x75, 0xB5,
+  0x77, 0xB7, 0xB6, 0x76, 0x72, 0xB2, 0xB3, 0x73, 0xB1, 0x71, 0x70, 0xB0,
+  0x50, 0x90, 0x91, 0x51, 0x93, 0x53, 0x52, 0x92, 0x96, 0x56, 0x57, 0x97,
+  0x55, 0x95, 0x94, 0x54, 0x9C, 0x5C, 0x5D, 0x9D, 0x5F, 0x9F, 0x9E, 0x5E,
+  0x5A, 0x9A, 0x9B, 0x5B, 0x99, 0x59, 0x58, 0x98, 0x88, 0x48, 0x49, 0x89,
+  0x4B, 0x8B, 0x8A, 0x4A, 0x4E, 0x8E, 0x8F, 0x4F, 0x8D, 0x4D, 0x4C, 0x8C,
+  0x44, 0x84, 0x85, 0x45, 0x87, 0x47, 0x46, 0x86, 0x82, 0x42, 0x43, 0x83,
+  0x41, 0x81, 0x80, 0x40
+};
+
+// TOF frame format
+//
+//   1B     1B      1B              1B            2B
+// | 0xA5 | 0x5A | distance-MSB | distance-LSB | crc-16 |
+//
+// Frame data saved for CRC calculation
+const static int TOF_DISTANCE_MSB_POS   = 2;
+const static int TOF_DISTANCE_LSB_POS   = 3;
+const static int TOF_CRC_CALC_DATA_LEN  = 4;
+static unsigned char frame_data[TOF_CRC_CALC_DATA_LEN] = {
+  TOF_SFD1, TOF_SFD2, 0, 0
+};
+
+USHORT usMBCRC16(UCHAR* pucFrame, USHORT usLen) {
+  UCHAR ucCRCHi = 0xFF;
+  UCHAR ucCRCLo = 0xFF;
+  int iIndex;
+  while (usLen--) {
+    iIndex = ucCRCLo ^ *(pucFrame++);
+    ucCRCLo = (UCHAR)(ucCRCHi ^ aucCRCHi[iIndex]);
+    ucCRCHi = aucCRCLo[iIndex];
+  }
+  return (USHORT)(ucCRCHi << 8 | ucCRCLo);
+}
+
+int isl2950_parser(const uint8_t* buffer, int length, bool* full_frame, int* dist)
 {
+  static TofFramingState state = TFS_NOT_STARTED;
+  static uint16_t crc16 = 0;
   int bytes_processed = 0;
 
-// SOME STUFFS
+  while (bytes_processed < length) {
+    uint8_t b = buffer[bytes_processed++];
+//    printf("parse byte 0x%02X \n", b);
+
+    switch (state) {
+    case TFS_NOT_STARTED:
+      if (b == TOF_SFD1) {
+        state = TFS_GOT_SFD1;
+  //      printf("Got SFD1 \n");
+      }
+      break;
+
+    case TFS_GOT_SFD1:
+      if (b == TOF_SFD2) {
+        state = TFS_GOT_SFD2;
+//        printf("Got SFD2 \n");
+      } else if (b == TOF_SFD1) {
+        state = TFS_GOT_SFD1;
+//        printf("Discard previous SFD1, Got new SFD1 \n");
+      } else {
+        state = TFS_NOT_STARTED;
+      }
+      break;
+
+    case TFS_GOT_SFD2:
+      frame_data[TOF_DISTANCE_MSB_POS] = b;
+      state = TFS_GOT_DATA1;
+//      printf("Got DATA1 0x%02X \n", b);
+      break;
+
+    case TFS_GOT_DATA1:
+      frame_data[TOF_DISTANCE_LSB_POS] = b;
+      state = TFS_GOT_DATA2;
+//      printf("Got DATA2 0x%02X \n", b);
+      // do crc calculation
+      crc16 = usMBCRC16(frame_data, TOF_CRC_CALC_DATA_LEN);
+      // convert endian
+      crc16 = (crc16 >> 8) | (crc16 << 8);
+      break;
+
+    case TFS_GOT_DATA2:
+      if (b == (crc16 >> 8)) {
+        state = TFS_GOT_CHECKSUM1;
+      } else {
+//        printf("Checksum invalid on high byte: 0x%02X, calculated: 0x%04X \n",b, crc16);
+        state = TFS_NOT_STARTED;
+      }
+      break;
+
+    case TFS_GOT_CHECKSUM1:
+      // Here, reset state to `NOT-STARTED` no matter crc ok or not
+      state = TFS_NOT_STARTED;
+      if (b == (crc16 & 0xFF)) {
+        printf("Checksum verified \n");
+        *dist = (frame_data[TOF_DISTANCE_MSB_POS] << 8) | frame_data[TOF_DISTANCE_LSB_POS];
+        *full_frame = true;
+        return bytes_processed;
+      } else {
+        printf("Checksum invalidon low byte: 0x%02X, calculated: 0x%04X \n",b, crc16);
+      }
+      break;
+
+    default:
+      printf("This should never happen. \n");
+      break;
+    }
+  }
+  // SOME STUFFS
   return bytes_processed;
 }

src/drivers/distance_sensor/airlango/isl2950_parser.h

@@ -40,6 +40,27 @@
 
 #pragma once
 
+// frame start delimiter
+#define TOF_SFD1      0xA5
+#define TOF_SFD2      0x5A
+
+typedef enum {
+  TFS_NOT_STARTED = 0,
+  TFS_GOT_SFD1,
+  TFS_GOT_SFD2,
+  TFS_GOT_DATA1,
+  TFS_GOT_DATA2,
+  TFS_GOT_CHECKSUM1,
+  TFS_GOT_CHECKSUM2,
+} TofFramingState;
+
+enum IslWorkingMode {
+  KEEP_HEIGHT = 0,
+  NUM_WORKING_MODE
+};
+
+
+// SF0X STYLE
 enum ISL2950_PARSE_STATE {
 	ISL2950_PARSE_STATE0_UNSYNC = 0,
 	ISL2950_PARSE_STATE1_SYNC,
@@ -50,4 +71,5 @@ enum ISL2950_PARSE_STATE {
 	ISL2950_PARSE_STATE6_GOT_CARRIAGE_RETURN
 };
 
-int isl2950_parser(char c, char *parserbuf, unsigned *parserbuf_index, enum ISL2950_PARSE_STATE *state, float *dist);
+
+int isl2950_parser(const uint8_t* buffer, int length, bool* full_frame, int* dist);