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LibrePilot/flight/libraries/ssp.c

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OP-1476 - fix bootloader for serial support
2014-09-07 22:56:11 +02:00
/***********************************************************************************************************
*
* NAME: ssp.c
* DESCRIPTION: simple serial protocol - packet based serial transport layer.
* AUTHOR: Joe Hlebasko
* HISTORY: Created 1/1/2010
*
* Packet Formats
* Format:
* +------+----+------+---------------------------+--------+
* | 225 | L1 | S# | App Data (0-254 bytes) | CRC 16 |
* +------+----+------+---------------------------+--------+
*
* 225 = sync byte, indicates start of a packet
* L1 = 1 byte for size of data payload. (sequence number is part of data payload.)
* S# = 1 byte for sequence number.
* Seq of 0 = seq # synchronise request, forces other end to reset receive sequence number to 1.
* sender of synchronise request will reset the tx seq number to 1
* Seq # of 1..127 = normal data packets. Sequence number is incremented by for each transmitted
* packet. Rolls over from 127 to 1.
* if most sig. bit is set then the packet is an ACK packet of data packet sequence number of the
* lower 7 bits (1..127)
* App Data may contain 0..254 bytes. The sequence number is consider part of the payload.
* CRC 16 - 16 bits of CRC values of Sequence # and data bytes.
*
* Protocol has two types of packets: data and ack packets. ACK packets have the most sig. bit set in the
* sequence number, this implies that valid sequence numbers are 1..127
*
* This protocol uses the concept of sequences numbers to determine if a given packet has been received. This
* requires both devices to be able to synchronize sequence numbers. This is accomplished by sending a packet
* length 1 and sequence number = 0. The receive then resets it's transmit sequence number to 1.
*
* ACTIVE_SYNCH is a version that will automatically send a synch request if it receives a synch packet. Only
* one device in the communication should do otherwise you end up with an endless loops of synchronization.
* Right now each side needs to manually issues a synch request.
*
* This protocol is best used in cases where one device is the master and the other is the slave, or a don't
* speak unless spoken to type of approach.
*
* The following are items are required to initialize a port for communications:
* 1. The number attempts for each packet
* 2. time to wait for an ack.
* 3. pointer to buffer to be used for receiving.
* 4. pointer to a buffer to be used for transmission
* 5. length of each buffer (rx and tx)
* 6. Four functions:
* 1. write byte = writes a byte out the serial port (or other comm device)
* 2. read byte = retrieves a byte from the serial port. Returns -1 if a byte is not available
* 3. callback = function to call when a valid data packet has been received. This function is responsible
* to do what needs to be done with the data when it is received. The primary mission of this function
* should be to copy the data to a private buffer out of the working receive buffer to prevent overrun.
* processing should be kept to a minimum.
* 4. get time = function should return the current time. Note that time units are not specified it just
* needs to be some measure of time that increments as time passes by. The timeout values for a given
* port should the units used/returned by the get time function.
*
* All of the state information of a communication port is contained in a Port_t structure. This allows this
* module to operature on multiple communication ports with a single code base.
*
* The ssp_ReceiveProcess and ssp_SendProcess functions need to be called to process data through the
* respective state machines. Typical implementation would have a serial ISR to pull bytes out of the UART
* and place into a circular buffer. The serial read function would then pull bytes out this buffer
* processing. The TX side has the write function placing bytes into a circular buffer with the TX ISR
* pulling bytes out of the buffer and putting into the UART. It is possible to run the receive process from
* the receive ISR but care must be taken on processing data when it is received to avoid holding up the ISR
* and sending ACK packets from the receive ISR.
*
***********************************************************************************************************/
/** INCLUDE FILES **/
#include <stdint.h>
#include <string.h>
#include <stdio.h>
#include <pios.h>
#include "ssp.h"
/** PRIVATE DEFINITIONS **/
#define SYNC 225 // Sync character used in Serial Protocol
#define ESC 224 // ESC character used in Serial Protocol
#define ESC_SYNC 1 // ESC_SYNC character used in Serial Protocol
#define ACK_BIT 0x80 // Ack bit, bit 7 of sequence number, 1 = Acknowledge, 0 =
// new packet
// packet location definitions.
#define LENGTH 0
#define SEQNUM 1
#define DATA 2
// Make larger sized integers from smaller sized integers
#define MAKEWORD16(ub, lb) ((uint16_t)0x0000 | ((uint16_t)(ub) << 8) | (uint16_t)(lb))
#define MAKEWORD32(uw, lw) ((uint32_t)(0x0UL | ((uint32_t)(uw) << 16) | (uint32_t)(lw)))
#define MAKEWORD32B(b3, b2, b1, b0) ((uint32_t)((uint32_t)(b3) << 24) | ((uint32_t)(b2) << 16) | ((uint32_t)(b1) << 8) | ((uint32_t)(b0))
// Used to extract smaller integers from larger sized intergers
#define LOWERBYTE(w) (uint8_t)((w) & 0x00ff)
#define UPPERBYTE(w) (uint8_t)(((w) & 0xff00) >> 8)
#define UPPERWORD(lw) (uint16_t)(((lw) & 0xffff0000) >> 16)
#define LOWERWORD(lw) (uint16_t)((lw) & 0x0000ffff)
// Macros to operate on a target and bitmask.
#define CLEARBIT(a, b) ((a) = (a) & ~(b))
#define SETBIT(a, b) ((a) = (a) | (b))
#define TOGGLEBIT(a, b) ((a) = (a) ^ (b))
// test bit macros operate using a bit mask.
#define ISBITSET(a, b) (((a) & (b)) == (b) ? TRUE : FALSE)
#define ISBITCLEAR(a, b) ((~(a) & (b)) == (b) ? TRUE : FALSE)
/** PRIVATE FUNCTIONS **/
// static void sf_SendSynchPacket( Port_t *thisport );
static uint16_t sf_checksum(uint16_t crc, uint8_t data);
static void sf_write_byte(Port_t *thisport, uint8_t c);
static void sf_SetSendTimeout(Port_t *thisport);
static uint16_t sf_CheckTimeout(Port_t *thisport);
static int16_t sf_DecodeState(Port_t *thisport, uint8_t c);
static int16_t sf_ReceiveState(Port_t *thisport, uint8_t c);
static void sf_SendPacket(Port_t *thisport);
static void sf_SendAckPacket(Port_t *thisport, uint8_t seqNumber);
static void sf_MakePacket(uint8_t *buf, const uint8_t *pdata, uint16_t length,
uint8_t seqNo);
static int16_t sf_ReceivePacket(Port_t *thisport);
/* Flag bit masks...*/
#define SENT_SYNCH (0x01)
#define ACK_RECEIVED (0x02)
#define ACK_EXPECTED (0x04)
#define SSP_AWAITING_ACK 0
#define SSP_ACKED 1
#define SSP_IDLE 2
/** PRIVATE DATA **/
static const uint16_t CRC_TABLE[] = { 0x0000, 0xC0C1, 0xC181, 0x0140, 0xC301,
0x03C0, 0x0280, 0xC241, 0xC601, 0x06C0,0x0780, 0xC741, 0x0500, 0xC5C1,
0xC481, 0x0440, 0xCC01, 0x0CC0, 0x0D80,0xCD41, 0x0F00, 0xCFC1, 0xCE81,
0x0E40, 0x0A00, 0xCAC1, 0xCB81, 0x0B40,0xC901, 0x09C0, 0x0880, 0xC841,
0xD801, 0x18C0, 0x1980, 0xD941, 0x1B00,0xDBC1, 0xDA81, 0x1A40, 0x1E00,
0xDEC1, 0xDF81, 0x1F40, 0xDD01, 0x1DC0,0x1C80, 0xDC41, 0x1400, 0xD4C1,
0xD581, 0x1540, 0xD701, 0x17C0, 0x1680,0xD641, 0xD201, 0x12C0, 0x1380,
0xD341, 0x1100, 0xD1C1, 0xD081, 0x1040,0xF001, 0x30C0, 0x3180, 0xF141,
0x3300, 0xF3C1, 0xF281, 0x3240, 0x3600,0xF6C1, 0xF781, 0x3740, 0xF501,
0x35C0, 0x3480, 0xF441, 0x3C00, 0xFCC1,0xFD81, 0x3D40, 0xFF01, 0x3FC0,
0x3E80, 0xFE41, 0xFA01, 0x3AC0, 0x3B80,0xFB41, 0x3900, 0xF9C1, 0xF881,
0x3840, 0x2800, 0xE8C1, 0xE981, 0x2940,0xEB01, 0x2BC0, 0x2A80, 0xEA41,
0xEE01, 0x2EC0, 0x2F80, 0xEF41, 0x2D00,0xEDC1, 0xEC81, 0x2C40, 0xE401,
0x24C0, 0x2580, 0xE541, 0x2700, 0xE7C1,0xE681, 0x2640, 0x2200, 0xE2C1,
0xE381, 0x2340, 0xE101, 0x21C0, 0x2080,0xE041, 0xA001, 0x60C0, 0x6180,
0xA141, 0x6300, 0xA3C1, 0xA281, 0x6240,0x6600, 0xA6C1, 0xA781, 0x6740,
0xA501, 0x65C0, 0x6480, 0xA441, 0x6C00,0xACC1, 0xAD81, 0x6D40, 0xAF01,
0x6FC0, 0x6E80, 0xAE41, 0xAA01, 0x6AC0,0x6B80, 0xAB41, 0x6900, 0xA9C1,
0xA881, 0x6840, 0x7800, 0xB8C1, 0xB981,0x7940, 0xBB01, 0x7BC0, 0x7A80,
0xBA41, 0xBE01, 0x7EC0, 0x7F80, 0xBF41,0x7D00, 0xBDC1, 0xBC81, 0x7C40,
0xB401, 0x74C0, 0x7580, 0xB541, 0x7700,0xB7C1, 0xB681, 0x7640, 0x7200,
0xB2C1, 0xB381, 0x7340, 0xB101, 0x71C0,0x7080, 0xB041, 0x5000, 0x90C1,
0x9181, 0x5140, 0x9301, 0x53C0, 0x5280,0x9241, 0x9601, 0x56C0, 0x5780,
0x9741, 0x5500, 0x95C1, 0x9481, 0x5440,0x9C01, 0x5CC0, 0x5D80, 0x9D41,
0x5F00, 0x9FC1, 0x9E81, 0x5E40, 0x5A00,0x9AC1, 0x9B81, 0x5B40, 0x9901,
0x59C0, 0x5880, 0x9841, 0x8801, 0x48C0,0x4980, 0x8941, 0x4B00, 0x8BC1,
0x8A81, 0x4A40, 0x4E00, 0x8EC1, 0x8F81,0x4F40, 0x8D01, 0x4DC0, 0x4C80,
0x8C41, 0x4400, 0x84C1, 0x8581, 0x4540,0x8701, 0x47C0, 0x4680, 0x8641,
0x8201, 0x42C0, 0x4380, 0x8341, 0x4100,0x81C1, 0x8081, 0x4040 };
/** EXTERNAL DATA **/
/** EXTERNAL FUNCTIONS **/
/** VERIFICATION FUNCTIONS **/
/***********************************************************************************************************/
/*!
* \brief Initializes the communication port for use
* \param thisport = pointer to port structure to initialize
* \param info = config struct with default values.
* \return None.
*
* \note
* Must be called before calling the Send or REceive process functions.
*/
void ssp_Init(Port_t *thisport, const PortConfig_t *const info)
{
thisport->pfCallBack = info->pfCallBack;
thisport->pfSerialRead = info->pfSerialRead;
thisport->pfSerialWrite = info->pfSerialWrite;
thisport->pfGetTime = info->pfGetTime;
thisport->maxRetryCount = info->max_retry;
thisport->timeoutLen = info->timeoutLen;
thisport->txBufSize = info->txBufSize;
thisport->rxBufSize = info->rxBufSize;
thisport->txBuf = info->txBuf;
thisport->rxBuf = info->rxBuf;
thisport->retryCount = 0;
thisport->sendSynch = FALSE; // TRUE;
thisport->rxSeqNo = 255;
thisport->txSeqNo = 255;
thisport->SendState = SSP_IDLE;
}
/*!
* \brief Runs the send process, checks for receipt of ack, timeouts and resends if needed.
* \param thisport = which port to use
* \return SSP_TX_WAITING - waiting for a valid ACK to arrive
* \return SSP_TX_TIMEOUT - failed to receive a valid ACK in the timeout period, after retrying.
* \return SSP_TX_IDLE - not expecting a ACK packet (no current transmissions in progress)
* \return SSP_TX_ACKED - valid ACK received before timeout period.
*
* \note
*
*/
int16_t ssp_SendProcess(Port_t *thisport)
{
int16_t value = SSP_TX_WAITING;
if (thisport->SendState == SSP_AWAITING_ACK) {
if (sf_CheckTimeout(thisport) == TRUE) {
if (thisport->retryCount < thisport->maxRetryCount) {
// Try again
sf_SendPacket(thisport);
sf_SetSendTimeout(thisport);
value = SSP_TX_WAITING;
} else {
// Give up, # of trys has exceded the limit
value = SSP_TX_TIMEOUT;
CLEARBIT(thisport->flags, ACK_RECEIVED);
thisport->SendState = SSP_IDLE;
}
} else {
value = SSP_TX_WAITING;
}
} else if (thisport->SendState == SSP_ACKED) {
SETBIT(thisport->flags, ACK_RECEIVED);
value = SSP_TX_ACKED;
thisport->SendState = SSP_IDLE;
} else {
thisport->SendState = SSP_IDLE;
value = SSP_TX_IDLE;
}
return value;
}
/*!
* \brief Runs the receive process. fetches a byte at a time and runs the byte through the protocol receive state machine.
* \param thisport - which port to use.
* \return receive status.
*
* \note
*
*/
int16_t ssp_ReceiveProcess(Port_t *thisport)
{
int16_t b;
int16_t packet_status = SSP_RX_IDLE;
do {
b = thisport->pfSerialRead(); // attempt to read a char from the serial buffer
if (b != -1) {
packet_status = sf_ReceiveState(thisport, b); // process the newly received byte in the receive state machine
}
// keep going until either we received a full packet or there are no more bytes to process
} while (packet_status != SSP_RX_COMPLETE && b != -1);
return packet_status;
}
/*!
* \brief processes a single byte through the receive state machine.
* \param thisport = which port to use
* \return current receive status
*
* \note
*
*/
int16_t ssp_ReceiveByte(Port_t *thisport)
{
int16_t b;
int16_t packet_status = SSP_RX_IDLE;
b = thisport->pfSerialRead();
if (b != -1) {
packet_status = sf_ReceiveState(thisport, b);
}
return packet_status;
}
/*!
* \brief Sends a data packet and blocks until timeout or ack is received.
* \param thisport = which port to use
* \param data = pointer to data to send
* \param length = number of data bytes to send. Must be less than 254
* \return true = ack was received within number of retries
* \return false = ack was not received.
*
* \note
*
*/
uint16_t ssp_SendDataBlock(Port_t *thisport, uint8_t *data, uint16_t length)
{
int16_t packet_status = SSP_TX_WAITING;
packet_status = ssp_SendData(thisport, data, length); // send the data
while (packet_status == SSP_TX_WAITING) { // check the status
(void)ssp_ReceiveProcess(thisport); // process any bytes received.
packet_status = ssp_SendProcess(thisport); // check the send status
}
return packet_status == SSP_TX_ACKED; // figure out what happened to the packet
}
/*!
* \brief sends a chunk of data and does not block
* \param thisport = which port to use
* \param data = pointer to data to send
* \param length = number of bytes to send
* \return SSP_TX_BUFOVERRUN = tried to send too much data
* \return SSP_TX_WAITING = data sent and waiting for an ack to arrive
* \return SSP_TX_BUSY = a packet has already been sent, but not yet acked
*
* \note
*
*/
int16_t ssp_SendData(Port_t *thisport, const uint8_t *data,
const uint16_t length)
{
int16_t value = SSP_TX_WAITING;
if ((length + 2) > thisport->txBufSize) {
// TRYING to send too much data.
value = SSP_TX_BUFOVERRUN;
} else if (thisport->SendState == SSP_IDLE) {
#ifdef ACTIVE_SYNCH
if (thisport->sendSynch == TRUE) {
sf_SendSynchPacket(thisport);
}
#endif
#ifdef SYNCH_SEND
if (length == 0) {
// TODO this method could allow a task/user to start a synchronisation step if a zero is mistakenly passed to this function.
// could add a check for a NULL data pointer, or use some sort of static flag that can only be accessed by a static function
// that must be called before calling this function.
// we are attempting to send a synch packet
thisport->txSeqNo = 0; // make this zero to cause the other end to re-synch with us
SETBIT(thisport->flags, SENT_SYNCH);
} else {
// we are sending a data packet
CLEARBIT(thisport->txSeqNo, ACK_BIT); // make sure we are not sending a ACK packet
thisport->txSeqNo++; // update the sequence number.
if (thisport->txSeqNo > 0x7F) { // check for sequence number rollover
thisport->txSeqNo = 1; // if we do have rollover then reset to 1 not zero,
// zero is reserviced for synchronization requests
}
}
#else
CLEARBIT(thisport->txSeqNo, ACK_BIT); // make sure we are not sending a ACK packet
thisport->txSeqNo++; // update the sequence number.
if (thisport->txSeqNo > 0x7F) { // check for sequence number rollover
thisport->txSeqNo = 1; // if we do have rollover then reset to 1 not zero,
// zero is reserved for synchronization requests
}
#endif /* ifdef SYNCH_SEND */
CLEARBIT(thisport->flags, ACK_RECEIVED);
thisport->SendState = SSP_AWAITING_ACK;
value = SSP_TX_WAITING;
thisport->retryCount = 0; // zero out the retry counter for this transmission
sf_MakePacket(thisport->txBuf, data, length, thisport->txSeqNo);
sf_SendPacket(thisport); // punch out the packet to the serial port
sf_SetSendTimeout(thisport); // do the timeout values
} else {
// error we are already sending a packet. Need to wait for the current packet to be acked or timeout.
value = SSP_TX_BUSY;
}
return value;
}
/*!
* \brief Attempts to synchronize the sequence numbers with the other end of the connectin.
* \param thisport = which port to use
* \return true = success
* \return false = failed to receive an ACK to our synch request
*
* \note
* A. send a packet with a sequence number equal to zero
* B. if timed out then:
* send synch packet again
* increment try counter
* if number of tries exceed maximum try limit then exit
* C. goto A
*/
uint16_t ssp_Synchronise(Port_t *thisport)
{
int16_t packet_status;
#ifndef USE_SENDPACKET_DATA
thisport->txSeqNo = 0; // make this zero to cause the other end to re-synch with us
SETBIT(thisport->flags, SENT_SYNCH);
// TODO - should this be using ssp_SendPacketData()??
sf_MakePacket(thisport->txBuf, NULL, 0, thisport->txSeqNo); // construct the packet
sf_SendPacket(thisport);
sf_SetSendTimeout(thisport);
thisport->SendState = SSP_AWAITING_ACK;
packet_status = SSP_TX_WAITING;
#else
packet_status = ssp_SendData(thisport, NULL, 0);
#endif
while (packet_status == SSP_TX_WAITING) { // we loop until we time out.
(void)ssp_ReceiveProcess(thisport); // do the receive process
packet_status = ssp_SendProcess(thisport); // do the send process
}
thisport->sendSynch = FALSE;
return packet_status == SSP_TX_ACKED;
}
/*!
* \brief sends out a preformatted packet for a give port
* \param thisport = which port to use.
* \return none.
*
* \note
* Packet should be formed through the use of sf_MakePacket before calling this function.
*/
static void sf_SendPacket(Port_t *thisport)
{
// add 3 to packet data length for: 1 length + 2 CRC (packet overhead)
uint8_t packetLen = thisport->txBuf[LENGTH] + 3;
// use the raw serial write function so the SYNC byte does not get 'escaped'
thisport->pfSerialWrite(SYNC);
for (uint8_t x = 0; x < packetLen; x++) {
sf_write_byte(thisport, thisport->txBuf[x]);
}
thisport->retryCount++;
}
/*!
* \brief converts data to transport layer protocol packet format.
* \param txbuf = buffer to use when forming the packet
* \param pdata = pointer to data to use
* \param length = number of bytes to use
* \param seqNo = sequence number of this packet
* \return none.
*
* \note
* 1. This function does not try to interpret ACK or SYNCH packets. This should
* be done by the caller of this function.
* 2. This function will attempt to format all data upto the size of the tx buffer.
* Any extra data beyond that will be ignored.
* 3. TODO: Should this function return an error if data length to be sent is greater th tx buffer size?
*
*/
void sf_MakePacket(uint8_t *txBuf, const uint8_t *pdata, uint16_t length,
uint8_t seqNo)
{
uint16_t crc = 0xffff;
uint16_t bufPos = 0;
uint8_t b;
// add 1 for the seq. number
txBuf[LENGTH] = length + 1;
txBuf[SEQNUM] = seqNo;
crc = sf_checksum(crc, seqNo);
length = length + 2; // add two for the length and seqno bytes which are added before the loop.
for (bufPos = 2; bufPos < length; bufPos++) {
b = *pdata++;
txBuf[bufPos] = b;
crc = sf_checksum(crc, b); // update CRC value
}
txBuf[bufPos++] = LOWERBYTE(crc);
txBuf[bufPos] = UPPERBYTE(crc);
}
/*!
* \brief sends out an ack packet to given sequence number
* \param thisport = which port to use
* \param seqNumber = sequence number of the packet we would like to ack
* \return none.
*
* \note
*
*/
static void sf_SendAckPacket(Port_t *thisport, uint8_t seqNumber)
{
uint8_t AckSeqNumber = SETBIT(seqNumber, ACK_BIT);
// create the packet, note we pass AckSequenceNumber directly
sf_MakePacket(thisport->txBuf, NULL, 0, AckSeqNumber);
sf_SendPacket(thisport);
// we don't set the timeout for an ACK because we don't ACK our ACKs in this protocol
}
/*!
* \brief writes a byte out the output channel. Adds escape byte where needed
* \param thisport = which port to use
* \param c = byte to send
* \return none.
*
* \note
*
*/
static void sf_write_byte(Port_t *thisport, uint8_t c)
{
if (c == SYNC) { // check for SYNC byte
thisport->pfSerialWrite(ESC); // since we are not starting a packet we must ESCAPE the SYNCH byte
thisport->pfSerialWrite(ESC_SYNC); // now send the escaped synch char
} else if (c == ESC) { // Check for ESC character
thisport->pfSerialWrite(ESC); // if it is, we need to send it twice
thisport->pfSerialWrite(ESC);
} else {
thisport->pfSerialWrite(c); // otherwise write the byte to serial port
}
}
/************************************************************************************************************
*
* NAME: uint16_t ssp_crc16( uint16_t crc, uint16_t data )
* DESCRIPTION: Uses crc_table to calculate new crc
* ARGUMENTS:
* arg1: crc
* arg2: data - byte to calculate into CRC
* RETURN: New crc
* CREATED: 5/8/02
*
*************************************************************************************************************/
/*!
* \brief calculates the new CRC value for 'data'
* \param crc = current CRC value
* \param data = new byte
* \return updated CRC value
*
* \note
*
*/
static uint16_t sf_checksum(uint16_t crc, uint8_t data)
{
#ifdef SPP_USES_CRC
return (crc >> 8) ^ CRC_TABLE[(crc ^ data) & 0x00FF];
#else
uint8_t cka = crc & 0xff;
uint8_t ckb = (crc >> 8) & 0xff;
cka += data;
ckb += cka;
return cka | ckb << 8;
#endif
}
/*!
* \brief sets the timeout for the given packet
* \param thisport = which port to use
* \return none.
*
* \note
*
*/
static void sf_SetSendTimeout(Port_t *thisport)
{
uint32_t timeout;
timeout = thisport->pfGetTime() + thisport->timeoutLen;
thisport->timeout = timeout;
}
/*!
* \brief checks to see if a timeout occured
* \param thisport = which port to use
* \return true = a timeout has occurred
* \return false = has not timed out
*
* \note
*
*/
static uint16_t sf_CheckTimeout(Port_t *thisport)
{
uint16_t retval = FALSE;
uint32_t current_time;
current_time = thisport->pfGetTime();
if (current_time > thisport->timeout) {
retval = TRUE;
}
return retval;
}
/****************************************************************************
* NAME: sf_ReceiveState
* DESC: Implements the receive state handling code for escaped and unescaped data
* ARGS: thisport - which port to operate on
* c - incoming byte
* RETURN:
* CREATED:
* NOTES:
* 1. change from using pointer to functions.
****************************************************************************/
/*!
* \brief implements the receive state handling code for escaped and unescaped data
* \param thisport = which port to use
* \param c = byte to process through the receive state machine
* \return receive status
*
* \note
*
*/
static int16_t sf_ReceiveState(Port_t *thisport, uint8_t c)
{
int16_t retval = SSP_RX_RECEIVING;
switch (thisport->InputState) {
case state_unescaped_e:
if (c == SYNC) {
thisport->DecodeState = decode_len1_e;
} else if (c == ESC) {
thisport->InputState = state_escaped_e;
} else {
retval = sf_DecodeState(thisport, c);
}
break; // end of unescaped state.
case state_escaped_e:
thisport->InputState = state_unescaped_e;
if (c == SYNC) {
thisport->DecodeState = decode_len1_e;
} else if (c == ESC_SYNC) {
retval = sf_DecodeState(thisport, SYNC);
} else {
retval = sf_DecodeState(thisport, c);
}
break; // end of the escaped state.
default:
break;
}
return retval;
}
/****************************************************************************
* NAME: sf_DecodeState
* DESC: Implements the receive state finite state machine
* ARGS: thisport - which port to operate on
* c - incoming byte
* RETURN:
* CREATED:
* NOTES:
* 1. change from using pointer to functions.
****************************************************************************/
/*!
* \brief implements the receiving decoding state machine
* \param thisport = which port to use
* \param c = byte to process
* \return receive status
*
* \note
*
*/
static int16_t sf_DecodeState(Port_t *thisport, uint8_t c)
{
int16_t retval;
switch (thisport->DecodeState) {
case decode_idle_e:
// 'c' is ignored in this state as the only way to leave the idle state is
// recognition of the SYNC byte in the sf_ReceiveState function.
retval = SSP_RX_IDLE;
break;
case decode_len1_e:
thisport->rxBuf[LENGTH] = c;
thisport->rxBufLen = c;
if (thisport->rxBufLen <= thisport->rxBufSize) {
thisport->DecodeState = decode_seqNo_e;
retval = SSP_RX_RECEIVING;
} else {
thisport->DecodeState = decode_idle_e;
retval = SSP_RX_IDLE;
}
break;
case decode_seqNo_e:
thisport->rxBuf[SEQNUM] = c;
thisport->crc = 0xffff;
thisport->rxBufLen--; // subtract 1 for the seq. no.
thisport->rxBufPos = 2;
thisport->crc = sf_checksum(thisport->crc, c);
if (thisport->rxBufLen > 0) {
thisport->DecodeState = decode_data_e;
} else {
thisport->DecodeState = decode_crc1_e;
}
retval = SSP_RX_RECEIVING;
break;
case decode_data_e:
thisport->rxBuf[(thisport->rxBufPos)++] = c;
thisport->crc = sf_checksum(thisport->crc, c);
if (thisport->rxBufPos == (thisport->rxBufLen + 2)) {
thisport->DecodeState = decode_crc1_e;
}
retval = SSP_RX_RECEIVING;
break;
case decode_crc1_e:
thisport->crc = sf_checksum(thisport->crc, c);
thisport->DecodeState = decode_crc2_e;
retval = SSP_RX_RECEIVING;
break;
case decode_crc2_e:
thisport->DecodeState = decode_idle_e;
// verify the CRC value for the packet
if (sf_checksum(thisport->crc, c) == 0) {
// TODO shouldn't the return value of sf_ReceivePacket() be checked?
sf_ReceivePacket(thisport);
retval = SSP_RX_COMPLETE;
} else {
thisport->RxError++;
retval = SSP_RX_IDLE;
}
break;
default:
thisport->DecodeState = decode_idle_e; // unknown state so reset to idle state and wait for the next start of a packet.
retval = SSP_RX_IDLE;
break;
}
return retval;
}
/************************************************************************************************************
*
* NAME: int16_t sf_ReceivePacket( )
* DESCRIPTION: Receive one packet, assumed that data is in rec.buff[]
* ARGUMENTS:
* RETURN: 0 . no new packet was received, could be ack or same packet
* 1 . new packet received
* SSP_PACKET_?
* SSP_PACKET_COMPLETE
* SSP_PACKET_ACK
* CREATED: 5/8/02
*
*************************************************************************************************************/
/*!
* \brief receive one packet. calls the callback function if needed.
* \param thisport = which port to use
* \return true = valid data packet received.
* \return false = otherwise
*
* \note
*
* Created: Oct 7, 2010 12:07:22 AM by joe
*/
static int16_t sf_ReceivePacket(Port_t *thisport)
{
int16_t value = FALSE;
if (ISBITSET(thisport->rxBuf[SEQNUM], ACK_BIT)) {
// Received an ACK packet, need to check if it matches the previous sent packet
if ((thisport->rxBuf[SEQNUM] & 0x7F) == (thisport->txSeqNo & 0x7f)) {
// It matches the last packet sent by us
SETBIT(thisport->txSeqNo, ACK_BIT);
thisport->SendState = SSP_ACKED;
value = FALSE;
}
// else ignore the ACK packet
} else {
// Received a 'data' packet, figure out what type of packet we received...
if (thisport->rxBuf[SEQNUM] == 0) {
// Synchronize sequence number with host
#ifdef ACTIVE_SYNCH
thisport->sendSynch = TRUE;
#endif
sf_SendAckPacket(thisport, thisport->rxBuf[SEQNUM]);
thisport->rxSeqNo = 0;
value = FALSE;
} else if (thisport->rxBuf[SEQNUM] == thisport->rxSeqNo) {
// Already seen this packet, just ack it, don't act on the packet.
sf_SendAckPacket(thisport, thisport->rxBuf[SEQNUM]);
value = FALSE;
} else {
// New Packet
thisport->rxSeqNo = thisport->rxBuf[SEQNUM];
// Let the application do something with the data/packet.
if (thisport->pfCallBack != NULL) {
// skip the first two bytes (length and seq. no.) in the buffer.
thisport->pfCallBack(&(thisport->rxBuf[2]), thisport->rxBufLen);
}
// after we send the ACK, it is possible for the host to send a new packet.
// Thus the application needs to copy the data and reset the receive buffer
// inside of thisport->pfCallBack()
sf_SendAckPacket(thisport, thisport->rxBuf[SEQNUM]);
value = TRUE;
}
}
return value;
}
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