C51+CH375 USB disk reading example

I found a ready-made example. For reading and writing USB flash drives, the file system is a big problem. I still haven't figured it out yet. I'll save this program first and study it slowly later.

     The author's programming standards are good, with rich comments, and are worth learning.

#include  
#include "CH375INC.H" 
#include /* The following definitions are applicable to MCS-51 MCU */ 
#define UINT8 unsigned char 
#define UINT16 unsigned short 
#define UINT32 unsigned long 
#define UINT8X unsigned char xdata 
#define UINT8VX unsigned char volatile xdata 
UINT8VX CH375_CMD_PORT _at_ 0xBDF1; /* I/O address of CH375 command port */ 
UINT8VX CH375_DAT_PORT _at_ 0xBCF0; /* I/O address of CH375 data port */ 
#define CH375_INT_WIRE INT0 /* P3.2, connected to INT# pin of CH375, used to query 
interrupt  status */
UINT8X DISK_BUFFER[512*32] _at_ 0x0000; /* The starting address of the external RAM data buffer */ 

UINT32 DiskStart; /* The starting absolute sector number LBA of the logical disk */ 
UINT8 SecPerClus; /* The number of sectors per cluster of the logical disk */ 
UINT8 RsvdSecCnt; /* The number of reserved sectors of the logical disk */ 
UINT16 ; FATSz16; /* The number of sectors occupied by the FAT table of the FAT16 logical disk */  


/* ********** Hardware USB interface layer, this layer cannot be omitted anyway, the microcontroller must always interface with CH375 */ 

void mDelaymS( UINT8 delay ) { 
  UINT8 i, j, c; 
  for ( i = delay; i != 0; i -- ) { 
    for ( j = 200; j != 0; j -- ) c += 3; 
    for ( j = 200; j != 0; j -- ) c += 3; 
  } 
} 

void CH375_WR_CMD_PORT( UINT8 cmd ) { /* Write command to the command port of CH375 */ 
  CH375_CMD_PORT=cmd; 
  for ( cmd = 2; cmd != 0; cmd -- ); /* There should be a delay of 2uS before and after issuing the command code */ 
} 
void CH375_WR_DAT_PORT( UINT8 dat ) { /* Write data to the data port of CH375 */ 
  CH375_DAT_PORT=dat; /* Because the MCS51 microcontroller is slow, there is actually no need for delay */
} 
UINT8 CH375_RD_DAT_PORT( void ) { /* Read data from the data port of CH375 */ 
  return( CH375_DAT_PORT ); /* Because the MCS51 microcontroller is slow, there is actually no need for delay */ 
} 
UINT8 mWaitInterrupt( void ) { /* Wait for CH375 interrupt and get status, return operation status */ 
  while( CH375_INT_WIRE ); /* Query and wait for CH375 operation completion interrupt (INT# low level) */ 
  CH375_WR_CMD_PORT( CMD_GET_STATUS ); /* Generate operation completion interrupt, get interrupt status */ 
  return( CH375_RD_DAT_PORT() ); 
} 

/* ********** BulkOnly transmission protocol layer, built-in by CH375, no need to write MCU program */ 

/* ********** RBC/SCSI command layer, although built-in by CH375, but need to write program to issue commands and send and receive data   
*/ 

UINT8 mInitDisk( void ) { /* Initialize disk */ 
  UINT8 Status; 
  CH375_WR_CMD_PORT( CMD_GET_STATUS ); /* Generate operation completion interrupt, get interrupt status */ 
  Status = CH375_RD_DAT_PORT() ); 
  if ( Status == USB_INT_DISCONNECT ) return( Status ); /* USB device disconnected */ 
  CH375_WR_CMD_PORT( CMD_DISK_INIT ); /* Initialize USB storage */ 
  Status = mWaitInterrupt( ); /* Wait for interrupt and get status */ 
  if ( Status != USB_INT_SUCCESS ) return(Status ); /* Error occurred */ 
  CH375_WR_CMD_PORT( CMD_DISK_SIZE ); /* Get the capacity of USB storage */ 
  Status = mWaitInterrupt( ); /* Wait for interrupt and get status */ 
  if ( Status != USB_INT_SUCCESS ) { /* Retry if error occurs */ 
/* For CH375A chip, it is recommended to execute CMD_DISK_R_SENSE command once here */ 
    mDelaymS( 250 ); 
    CH375_WR_CMD_PORT( CMD_DISK_SIZE ); /* Get the capacity of USB storage */ 
    Status = mWaitInterrupt() ); /* Wait for interrupt and get status */ 
  } 
  if ( Status != USB_INT_SUCCESS ) return( Status ); /* Error occurred */ 
  return( 0 ); /* USB disk has been successfully initialized */ 
}  


UINT8 mReadSector( UINT32 iLbaStart, UINT8 iSectorCount, UINT8X *oDataBuffer )  
{ 
  UINT16 mBlockCount; 
  UINT8 c; 
  CH375_WR_CMD_PORT( CMD_DISK_READ ); /* Read data block from USB storage */ 
  CH375_WR_DAT_PORT( (UINT8)iLbaStart ); /* The lowest 8 bits of LBA */ 
  CH375_WR_DAT_PORT( (UINT8)( iLbaStart >> 8 ) ); 
  CH375_WR_DAT_PORT( (UINT8)( iLbaStart >> 16 ) ); 
  CH375_WR_DAT_PORT( (UINT8)( iLbaStart >> 24 ) ); /* LBA highest 8 bits */ 
  CH375_WR_DAT_PORT( iSectorCount ); /* Number of sectors */ 
  for ( mBlockCount = iSectorCount * 8; mBlockCount != 0; mBlockCount -- ) { 
    c = mWaitInterrupt() ); /* Wait for interrupt and get status */ 
    if ( c == USB_INT_DISK_READ ) { /* Wait for interrupt and get status, request data read */ 
      CH375_WR_CMD_PORT( CMD_RD_USB_DATA ); /* Read data block from CH375 buffer */ 
      c = CH375_RD_DAT_PORT() ); /* Length of subsequent data */ 
      while ( c -- ) *oDataBuffer++ = CH375_RD_DAT_PORT( ); 
      CH375_WR_CMD_PORT( CMD_DISK_RD_GO ); /* Continue to execute the read operation of USB storage */ 
    } 
    else break; /* Return error status */ 
  } 
  if ( mBlockCount == 0 ) { 
    c = mWaitInterrupt( ); /* Wait for interrupt and get status*/ 
    if ( c== USB_INT_SUCCESS ) return( 0 ); /* Operation successful */ 
  } 
  return( c ); /* Operation failed */ 
}  


/* ********** FAT file system layer, this layer of program volume is actually larger, but this program only demonstrates very simple functions, 
so it  is simplified */

UINT16 mGetPointWord( UINT8X *iAddr ) { /* Get word data, because MCS51 is big endian format */ 
  return( iAddr[0] | (UINT16)iAddr[1] << 8 ); 
} 

UINT8 mIdenDisk( void ) { /* Identify and analyze the current logical disk */ 
  UINT8 Status; 
  DiskStart = 0; /* The following is a very simple analysis of the FAT file system. The official application should not be so 
simple  */
  Status = mReadSector( 0, 1, DISK_BUFFER ); /* Read the logical disk boot information */ 
  if ( Status != 0 ) return( Status ); 
  if ( DISK_BUFFER[0] != 0xEB && DISK_BUFFER[0] != 0xE9 ) { /* Not a logical boot 
sector  */
    DiskStart = DISK_BUFFER[0x1C6] | (UINT16)DISK_BUFFER[0x1C7] << 8 
        | (UINT32)DISK_BUFFER[0x1C8] << 16 | (UINT32)DISK_BUFFER[0x1C9] << 24; 
    Status = mReadSector( DiskStart, 1, DISK_BUFFER ); 
    if ( Status != 0 ) return( Status ); 
  } 
  SecPerClus = DISK_BUFFER[0x0D]; /* Number of sectors per cluster */ 
  RsvdSecCnt = DISK_BUFFER[0x0E]; /* Number of reserved sectors of the logical disk */ 
  FATSz16 = mGetPointWord( &DISK_BUFFER[0x16] ); /* Number of sectors occupied by the FAT table */ 
  return( 0 ); /* Success */ 
} 

UINT16 mLinkCluster( UINT16 iCluster ) { /* Get the link cluster of the specified cluster number */ 
/* Input: iCluster current cluster number, Return: original linked cluster number, if it is 0, it means error */ 
  UINT8 Status; 
  Status = mReadSector( DiskStart + RsvdSecCnt + iCluster / 256, 1,  
DISK_BUFFER ); 
  if ( Status != 0 ) return( 0 ); /* Error */ 
  return( mGetPointWord( &DISK_BUFFER[ ( iCluster + iCluster ) & 0x01FF ] ) ); 
} 

UINT32 mClusterToLba(UINT16 iCluster ) { /* Convert cluster number to absolute LBA sector address */ 
  return( DiskStart + RsvdSecCnt + FATSz16 * 2 + 32 + ( iCluster - 2 ) *  
SecPerClus ); 
}  


void mInitSTDIO( void ) { /* It is only used for debugging and displaying content to the PC, and 
has nothing to do with  */
  SCON = 0x50; PCON = 0x80; TMOD = 0x20; TH1 = 0xf3; TR1=1; TI=1; /* 24MHz,  
9600bps */ 
} 
void mStopIfError( UINT8 iErrCode ) { /* If an error occurs, stop running and display the error status */ 
  if ( iErrCode == 0 ) return; 
  printf( "Error status, %02X 
", (UINT16)iErrCode ); 
} 

main() { 
  UINT8 Status; 
  UINT8X *CurrentDir; 
  UINT16 Cluster; 
  mDelaymS( 200 ); /* Delay 200 milliseconds */ 
  mInitSTDIO( ); 
  CH375_WR_CMD_PORT( CMD_SET_USB_MODE ); /* Initialize CH375 and set USB working mode */ 
  CH375_WR_DAT_PORT( 6 ); /* Mode code, automatically detect USB device connection */ 
  while ( 1 ) { 
    printf( "Insert USB disk 
" ); 
    while ( mWaitInterrupt() != USB_INT_CONNECT ); /* Wait for USB disk connection */ 
    mDelaymS( 250 ); /* Delay waiting for USB disk to enter normal working state */ 
    Status = mInitDisk() ); /* Initialize USB disk, actually identify the type of USB disk, this step must be performed */ 
    mStopIfError( Status ); 
    Status = mIdenDisk() ); /* Identify and analyze USB disk file system, necessary operation */ 
    mStopIfError( Status ); 
    Status = mReadSector( DiskStart + RsvdSecCnt + FATSz16 * 2, 32,  
DISK_BUFFER ); 
    mStopIfError( Status ); /* Read the root directory of the FAT16 logical disk. Usually the root directory occupies 32 sectors  
*/ 
    for ( CurrentDir = DISK_BUFFER; CurrentDir[0] != 0; CurrentDir += 32 ) { 
      if ( ( CurrentDir[0x0B] & 0x08 ) == 0 && CurrentDir[0] != 0xE5 ) { 
        CurrentDir[0x0B] = 0; /* For easy display, set the end mark of the file name or directory name */ 
        printf( "Name: %s 
", CurrentDir ); /* Display through serial port output */ 
      } 
    } /* The above displays all file names in the root directory. The following opens the first file if it is C file */
    if ( (DISK_BUFFER[0x0B]&0x08)==0 && DISK_BUFFER[0]!=0xE5 && DISK_BUFFER[8] 
=='C' ) { 
      Cluster = mGetPointWord( &DISK_BUFFER[0x1A] ); /* First cluster of the file */ 
      while ( Cluster < 0xFFF8 ) { /* File cluster is not over */ 
        if ( Cluster == 0 ) mStopIfError( 0x8F ); /* For the first cluster, it may be a zero-length file  
*/ 
        Status = mReadSector( mClusterToLba( Cluster ), SecPerClus,  
DISK_BUFFER ); 
        mStopIfError( Status ); /* Read the first cluster into the buffer */ 
        DISK_BUFFER[30] = 0; printf( "Data: %s
", DISK_BUFFER ); /* Display the first line  
*/ 
        Cluster = mLinkCluster( Cluster ); /* Get the link cluster, return 0 to indicate an error */ 
      } 
    } 
    while ( mWaitInterrupt() != USB_INT_DISCONNECT ); /* Wait for the USB flash drive to be unplugged */ 
    mDelaymS( 250 ); 
  } 
}