CanFestival 的buildPDO解析

/*!
**功能：从机把第numPdo个TPDO对应的数据封装到Message 包中
**
** @param d
** @param numPdo TPDO_com TPDO communication parameters OD entry TPDO_map TPDO mapping parameters OD entry
** @param pdo can数据包
**
** @return
**/

UNS8 buildPDO (CO_Data * d, UNS8 numPdo, Message * pdo)
{

//TPDO 通讯参数 1800 h 的对象
  const indextable *TPDO_com = d->objdict + d->firstIndex->PDO_TRS + numPdo;

//映射参数 1A00 h的对象
  const indextable *TPDO_map = d->objdict + d->firstIndex->PDO_TRS_MAP + numPdo;

  UNS8 prp_j = 0x00;
  UNS32 offset = 0x00000000;
  const UNS8 *pMappingCount = (UNS8 *) TPDO_map->pSubindex[0].pObject;//pdo映射有效对象数

  pdo->cob_id = (UNS16) UNS16_LE(*(UNS32*)TPDO_com->pSubindex[1].pObject & 0x7FF);//支持的cob-id
  pdo->rtr = NOT_A_REQUEST;//非遥控帧

  MSG_WAR (0x3009, "  PDO CobId is : ",
           *(UNS32 *) TPDO_com->pSubindex[1].pObject);
  MSG_WAR (0x300D, "  Number of objects mapped : ", *pMappingCount);

  do
    {
      UNS8 dataType;            /* Unused */
      UNS8 tmp[] = { 0, 0, 0, 0, 0, 0, 0, 0 };  /* temporary space to hold bits */

      /* pointer fo the var which holds the mapping parameter of an mapping entry  */
      UNS32 *pMappingParameter =
        (UNS32 *) TPDO_map->pSubindex[prp_j + 1].pObject;
      UNS16 index = (UNS16) ((*pMappingParameter) >> 16);//获取索引
      UNS32 Size = (UNS32) (*pMappingParameter & (UNS32) 0x000000FF);     /* Size in bits *///数据类型

      /* get variable only if Size != 0 and Size is lower than remaining bits in the PDO */
      if (Size && ((offset + Size) <= 64))
        {
          UNS32 ByteSize = 1 + ((Size - 1) >> 3);        /*1->8 => 1 ; 9->16 => 2, ... */
          UNS8 subIndex =
            (UNS8) (((*pMappingParameter) >> (UNS8) 8) & (UNS32) 0x000000FF);//获取子索引

          MSG_WAR (0x300F, "  got mapping parameter : ", *pMappingParameter);
          MSG_WAR (0x3050, "    at index : ", TPDO_map->index);
          MSG_WAR (0x3051, "    sub-index : ", prp_j + 1);

          if (getODentry (d, index, subIndex, tmp, &ByteSize, &dataType, 0) !=
              OD_SUCCESSFUL)//取得数据
            {
              MSG_ERR (0x1013,
                       " Couldn't find mapped variable at index-subindex-size : ",
                       (UNS32) (*pMappingParameter));
              return 0xFF;
            }
          /* copy bit per bit in little endian */
          CopyBits ((UNS8) Size, ((UNS8 *) tmp), 0, 0,
                    (UNS8 *) & pdo->data[offset >> 3], (UNS8)(offset % 8), 0);

          offset += Size;
        }
      prp_j++;
    }
  while (prp_j < *pMappingCount);

  pdo->len = (UNS8)(1 + ((offset - 1) >> 3));

  MSG_WAR (0x3015, "  End scan mapped variable", 0);

  return 0;
}