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Working on the Datalink MS/TP layer - no working yet.

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This commit is contained in:
skarg
2006-08-14 13:59:07 +00:00
parent 0eca2b07ad
commit dafc55bf9f
4 changed files with 174 additions and 42 deletions
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bacnet-stack/mstp.c
+49 -23
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@@ -128,17 +128,14 @@ const unsigned Tusage_delay = 15;
/* larger values for this timeout, not to exceed 100 milliseconds.) */
const unsigned Tusage_timeout = 20;
unsigned MSTP_Create_Frame(uint8_t * buffer, /* where frame is loaded */
/* creates the 8 octet frame header */
unsigned MSTP_Create_Frame_Header(uint8_t * buffer, /* where frame is loaded */
unsigned buffer_len, /* amount of space available */
uint8_t frame_type, /* type of frame to send - see defines */
uint8_t destination, /* destination address */
uint8_t source, /* source address */
uint8_t * data, /* any data to be sent - may be null */
unsigned data_len)
uint8_t source) /* source address */
{ /* number of bytes of data (up to 501) */
uint8_t crc8 = 0xFF; /* used to calculate the crc value */
uint16_t crc16 = 0xFFFF; /* used to calculate the crc value */
unsigned index = 0; /* used to load the data portion of the frame */
/* not enough to do a header */
if (buffer_len < 8)
@@ -158,24 +155,53 @@ unsigned MSTP_Create_Frame(uint8_t * buffer, /* where frame is loaded */
crc8 = CRC_Calc_Header(buffer[6], crc8);
buffer[7] = ~crc8;
index = 8;
while (data_len && data && (index < buffer_len)) {
buffer[index] = *data;
crc16 = CRC_Calc_Data(buffer[index], crc16);
data++;
index++;
data_len--;
return 8; /* returns the frame length */
}
/* copies the PDU to a buffer while calculating its CRC checksum
The CRC checksum is appended to the last two octets. */
unsigned MSTP_Copy_PDU_CRC(uint8_t * buffer, /* where frame is loaded */
unsigned buffer_len, /* amount of space available */
uint16_t crc16, /* used to calculate the crc value */
uint8_t * data, /* any data to be sent - may be null */
unsigned data_len)
{
unsigned index = 0; /* offset into the buffer */
if (buffer && data && data_len && ((data_len + 2) < buffer_len))
{
for (index = 0; index < data_len; index++)
{
buffer[index] = data[index];
crc16 = CRC_Calc_Data(buffer[index], crc16);
}
crc16 = ~crc16;
buffer[data_len] = LO_BYTE(crc16);
buffer[data_len + 1] = HI_BYTE(crc16);
index = data_len + 2;
}
/* append the data CRC if necessary */
if (index > 8) {
if ((index + 2) <= buffer_len) {
crc16 = ~crc16;
buffer[index] = LO_BYTE(crc16);
index++;
buffer[index] = HI_BYTE(crc16);
index++;
} else
return 0;
return index;
}
unsigned MSTP_Create_Frame(uint8_t * buffer, /* where frame is loaded */
unsigned buffer_len, /* amount of space available */
uint8_t frame_type, /* type of frame to send - see defines */
uint8_t destination, /* destination address */
uint8_t source, /* source address */
uint8_t * data, /* any data to be sent - may be null */
unsigned data_len)
{ /* number of bytes of data (up to 501) */
uint16_t crc16 = 0xFFFF; /* used to calculate the crc value */
unsigned index = 0; /* used to load the data portion of the frame */
index = MSTP_Create_Frame_Header(buffer, buffer_len, frame_type,
destination, source);
if (data && data_len)
{
index += MSTP_Copy_PDU_CRC(&buffer[index], buffer_len - index,
crc16, data, data_len);
}
return index; /* returns the frame length */