一种可靠串口协议
[TOC]
协议
kiwi mini里的ble通信协议没有校验和类型，如果出错没法检测，log打印也难以辨认，非常不利于调试，因此需要重新定义一个新的协议并完成它。 我们可以借鉴Zigbee的串口通信协议，那么我们先看看Zigbee的做法和代码。
协议包括开始，结束，类型，长度，校验和数据。 协议将低于0x10的字符作为功能字符，0x01作为开始，0x03作为结束，其他预留。 那么如果类型，长度，校验和数据中出现了低于0x10的数据，就将它和0x10做异或运算^=，并在前面先发送0x02作为标志。
server端程序
static teSL_Status eSL_WriteMessage(uint16 u16Type, uint16 u16Length, uint8 *pu8Data)
{
int n;
uint8 u8CRC;
u8CRC = u8SL_CalculateCRC(u16Type, u16Length, pu8Data);
DBG_vPrintf(DBG_SERIALLINK_COMMS, "(%d, %d, %02x)\n", u16Type, u16Length, u8CRC);
if (verbosity >= 10)
{
char acBuffer[4096];
int iPosition = 0, i;
iPosition = sprintf(&acBuffer[iPosition], "Host->Node 0x%04X (Length % 4d)", u16Type, u16Length);
for (i = 0; i < u16Length; i++)
{
iPosition += sprintf(&acBuffer[iPosition], " 0x%02X", pu8Data[i]);
}
INF_vPrintf(T_TRUE, "%s\n", acBuffer);
}
/* Send start character */
if (iSL_TxByte(T_TRUE, SL_START_CHAR) < 0) return E_SL_ERROR;
/* Send message type */
if (iSL_TxByte(T_FALSE, (u16Type >> 8) & 0xff) < 0) return E_SL_ERROR;
if (iSL_TxByte(T_FALSE, (u16Type >> 0) & 0xff) < 0) return E_SL_ERROR;
/* Send message length */
if (iSL_TxByte(T_FALSE, (u16Length >> 8) & 0xff) < 0) return E_SL_ERROR;
if (iSL_TxByte(T_FALSE, (u16Length >> 0) & 0xff) < 0) return E_SL_ERROR;
/* Send message checksum */
if (iSL_TxByte(T_FALSE, u8CRC) < 0) return E_SL_ERROR;
/* Send message payload */
for(n = 0; n < u16Length; n++)
{
if (iSL_TxByte(T_FALSE, pu8Data[n]) < 0) return E_SL_ERROR;
}
/* Send end character */
if (iSL_TxByte(T_TRUE, SL_END_CHAR) < 0) return E_SL_ERROR;
return E_SL_OK;
}
static int iSL_TxByte(bool_t bSpecialCharacter, uint8 u8Data)
{
if(!bSpecialCharacter && (u8Data < 0x10))
{
u8Data ^= 0x10;
if (eSerial_Write(SL_ESC_CHAR) != E_SERIAL_OK) return -1;
//DBG_vPrintf(DBG_SERIALLINK_COMMS, " 0x%02x", SL_ESC_CHAR);
}
//DBG_vPrintf(DBG_SERIALLINK_COMMS, " 0x%02x", u8Data);
return eSerial_Write(u8Data);
}
teSerial_Status eSerial_Write(const uint8 data)
{
int err, attempts = 0;
DBG_vPrintf(DGB_SERIAL, "TX 0x%02x\n", data);
err = write(serial_fd,&data,1);
if (err < 0)
{
if (errno == EAGAIN)/*try again*/
{
for (attempts = 0; attempts <= 5; attempts++)
{
usleep(1000);
err = write(serial_fd,&data,1);
if (err < 0)
{
if ((errno == EAGAIN) && (attempts == 5))
{
ERR_vPrintf(T_TRUE, "Error writing to module after %d attempts(%s)", attempts, strerror(errno));
exit(-1);
}
}
else
{
break;
}
}
}
else
{
ERR_vPrintf(T_TRUE, "Error writing to module(%s)", strerror(errno));
exit(-1);
}
}
return E_SERIAL_OK;
}接收程序
static teSL_Status eSL_ReadMessage(uint16 *pu16Type, uint16 *pu16Length, uint16 u16MaxLength, uint8 *pu8Message)
{
static teSL_RxState eRxState = E_STATE_RX_WAIT_START;
static uint8 u8CRC;
uint8 u8Data;
static uint16 u16Bytes;
static bool_t bInEsc = T_FALSE;
while(bSL_RxByte(&u8Data))
{
DBG_vPrintf(DBG_SERIALLINK_COMMS, "0x%02x\n", u8Data);
switch(u8Data)
{
case SL_START_CHAR:
u16Bytes = 0;
bInEsc = T_FALSE;
DBG_vPrintf(DBG_SERIALLINK_COMMS, "RX Start\n");
eRxState = E_STATE_RX_WAIT_TYPEMSB;
break;
case SL_ESC_CHAR:
DBG_vPrintf(DBG_SERIALLINK_COMMS, "Got ESC\n");
bInEsc = T_TRUE;
break;
case SL_END_CHAR:
DBG_vPrintf(DBG_SERIALLINK_COMMS, "Got END\n");
if(*pu16Length > u16MaxLength)
{
/* Sanity check length before attempting to CRC the message */
DBG_vPrintf(DBG_SERIALLINK_COMMS, "Length > MaxLength\n");
eRxState = E_STATE_RX_WAIT_START;
break;
}
if(u8CRC == u8SL_CalculateCRC(*pu16Type, *pu16Length, pu8Message))
{
#if DBG_SERIALLINK
int i;
DBG_vPrintf(DBG_SERIALLINK, "RX Message type 0x%04x length %d: { ", *pu16Type, *pu16Length);
for (i = 0; i < *pu16Length; i++)
{
printf("0x%02x ", pu8Message[i]);
}
printf("}\n");
#endif /* DBG_SERIALLINK */
eRxState = E_STATE_RX_WAIT_START;
return E_SL_OK;
}
DBG_vPrintf(DBG_SERIALLINK_COMMS, "CRC BAD\n");
break;
default:
if(bInEsc)
{
u8Data ^= 0x10;
bInEsc = T_FALSE;
}
switch(eRxState)
{
case E_STATE_RX_WAIT_START:
break;
case E_STATE_RX_WAIT_TYPEMSB:
*pu16Type = (uint16)u8Data << 8;
eRxState++;
break;
case E_STATE_RX_WAIT_TYPELSB:
*pu16Type += (uint16)u8Data;
eRxState++;
break;
case E_STATE_RX_WAIT_LENMSB:
*pu16Length = (uint16)u8Data << 8;
eRxState++;
break;
case E_STATE_RX_WAIT_LENLSB:
*pu16Length += (uint16)u8Data;
DBG_vPrintf(DBG_SERIALLINK_COMMS, "Length %d\n", *pu16Length);
if(*pu16Length > u16MaxLength)
{
DBG_vPrintf(DBG_SERIALLINK_COMMS, "Length > MaxLength\n");
eRxState = E_STATE_RX_WAIT_START;
}
else
{
eRxState++;
}
break;
case E_STATE_RX_WAIT_CRC:
DBG_vPrintf(DBG_SERIALLINK_COMMS, "CRC %02x\n", u8Data);
u8CRC = u8Data;
eRxState++;
break;
case E_STATE_RX_WAIT_DATA:
if(u16Bytes < *pu16Length)
{
DBG_vPrintf(DBG_SERIALLINK_COMMS, "Data\n");
pu8Message[u16Bytes++] = u8Data;
}
break;
default:
DBG_vPrintf(DBG_SERIALLINK_COMMS, "Unknown state\n");
eRxState = E_STATE_RX_WAIT_START;
}
break;
}
}
return E_SL_NOMESSAGE;
}
static bool_t bSL_RxByte(uint8 *pu8Data)
{
if (eSerial_Read(pu8Data) == E_SERIAL_OK)
{
return T_TRUE;
}
else
{
return T_FALSE;
}
}
teSerial_Status eSerial_Read(uint8 *data)
{
signed char res;
res = read(serial_fd,data,1);
if (res > 0)
{
DBG_vPrintf(DGB_SERIAL, "RX 0x%02x\n", *data);
}
else
{
//printf("Serial read: %d\n", res);
if (res == 0)
{
//daemon_log(LOG_ERR, "Serial connection to module interrupted");
//bRunning = 0;
}
return E_SERIAL_NODATA;
}
return E_SERIAL_OK;
}CRC校验部分
static uint8 u8SL_CalculateCRC(uint16 u16Type, uint16 u16Length, uint8 *pu8Data)
{
int n;
uint8 u8CRC = 0;
u8CRC ^= (u16Type >> 8) & 0xff;
u8CRC ^= (u16Type >> 0) & 0xff;
u8CRC ^= (u16Length >> 8) & 0xff;
u8CRC ^= (u16Length >> 0) & 0xff;
for(n = 0; n < u16Length; n++)
{
u8CRC ^= pu8Data[n];
}
return(u8CRC);
}单片机端程序如下： log打印程序，我们使用一个类型作为log，把单片机端的打印输出到server端打印出来：
void vSL_LogSend(uint8 u8LogLen, const char *pu8LogBuffer)
{
uint8 n = 0;
uint8 u8CRC = 0;
uint8 u8Length = 0;
uint8 u8LogStart = 0;
// = strlen(pu8LogBuffer);
uint8 u8Temp = 0;
while ((u8LogLen - u8LogStart) != 0)
{
/* Send start character */
vSL_TxByte(TRUE, SL_START_CHAR);
/* Send message type */
vSL_TxByte(FALSE, (E_SL_MSG_LOG >> 8) & 0xff);
vSL_TxByte(FALSE, (E_SL_MSG_LOG >> 0) & 0xff);
u8CRC = ((E_SL_MSG_LOG >> 8) & 0xff) ^ ((E_SL_MSG_LOG >> 0) & 0xff);
for (u8Length = 0; u8Temp |= '\0'; u8Length++)
{
u8Temp = pu8LogBuffer[(u8LogStart + u8Length) & 0xFF];
u8CRC ^= u8Temp;
}
u8CRC ^= 0;
u8CRC ^= u8Length;
/* Send message length */
vSL_TxByte(FALSE, 0);
vSL_TxByte(FALSE, u8Length);
/* Send message checksum */
vSL_TxByte(FALSE, u8CRC);
/* Send message payload */
for(n = 0; n < u8Length; n++)
{
vSL_TxByte(FALSE, pu8LogBuffer[u8LogStart]);
u8LogStart++;
}
u8LogStart++;
/* Send end character */
vSL_TxByte(TRUE, SL_END_CHAR);
}
}
int strlen(const char *str)
{
//assert(str);
if(*str==NULL)
return 0;
else
return ( 1 + strlen( ++str ));
}
void vSL_TxByte(bool bSpecialCharacter, uint8 u8Data)
{
if(!bSpecialCharacter && u8Data < 0x10)
{
/* Send escape character and escape byte */
u8Data ^= 0x10;
DebugWriteUint8(SL_ESC_CHAR);
}
DebugWriteUint8(u8Data);
}串口的接收解码：
static int eSL_ReadMessage(uint16 *pu16Type, uint16 *pu16Length, uint16 u16MaxLength, uint8 *pu8Message, uint8 *psRecv)
{
static teSL_RxState eRxState = E_STATE_RX_WAIT_START;
static uint8 u8CRC;
uint8 u8Data;
static uint16 u16Bytes;
static bool bInEsc = FALSE;
while(*psRecv)
{
u8Data = *psRecv;
psRecv++;
switch(u8Data)
{
case SL_START_CHAR:
u16Bytes = 0;
bInEsc = FALSE;
eRxState = E_STATE_RX_WAIT_TYPEMSB;
break;
case SL_ESC_CHAR:
bInEsc = TRUE;
break;
case SL_END_CHAR:
if(*pu16Length > u16MaxLength)
{
/* Sanity check length before attempting to CRC the message */
eRxState = E_STATE_RX_WAIT_START;
break;
}
if(u8CRC == u8SL_CalculateCRC(*pu16Type, *pu16Length, pu8Message))
{
eRxState = E_STATE_RX_WAIT_START;
return 0;
}
break;
default:
if(bInEsc)
{
u8Data ^= 0x10;
bInEsc = FALSE;
}
switch(eRxState)
{
case E_STATE_RX_WAIT_START:
break;
case E_STATE_RX_WAIT_TYPEMSB:
*pu16Type = (uint16)u8Data << 8;
eRxState++;
break;
case E_STATE_RX_WAIT_TYPELSB:
*pu16Type += (uint16)u8Data;
eRxState++;
break;
case E_STATE_RX_WAIT_LENMSB:
*pu16Length = (uint16)u8Data << 8;
eRxState++;
break;
case E_STATE_RX_WAIT_LENLSB:
*pu16Length += (uint16)u8Data;
if(*pu16Length > u16MaxLength)
{
eRxState = E_STATE_RX_WAIT_START;
}
else
{
eRxState++;
}
break;
case E_STATE_RX_WAIT_CRC:
u8CRC = u8Data;
eRxState++;
break;
case E_STATE_RX_WAIT_DATA:
if(u16Bytes < *pu16Length)
{
pu8Message[u16Bytes++] = u8Data;
}
break;
default:
eRxState = E_STATE_RX_WAIT_START;
}
break;
}
}
return 1;
}串口写数据：
void vSL_WriteMessage(uint16 u16Type, uint16 u16Length, uint8 *pu8Data)
{
uint16 n;
uint8 u8CRC;
u8CRC = u8SL_CalculateCRC(u16Type, u16Length, pu8Data);
/* Send start character */
vSL_TxByte(TRUE, SL_START_CHAR);
/* Send message type */
vSL_TxByte(FALSE, (u16Type >> 8) & 0xff);
vSL_TxByte(FALSE, (u16Type >> 0) & 0xff);
/* Send message length */
vSL_TxByte(FALSE, (u16Length >> 8) & 0xff);
vSL_TxByte(FALSE, (u16Length >> 0) & 0xff);
/* Send message checksum */
vSL_TxByte(FALSE, u8CRC);
/* Send message payload */
for(n = 0; n < u16Length; n++)
{
vSL_TxByte(FALSE, pu8Data[n]);
}
/* Send end character */
vSL_TxByte(TRUE, SL_END_CHAR);
}CRC校验使用同样程序。
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