root / trunk / bootloader / packet.c @ 287
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#include <packet.h> |
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/**
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* @brief Packet handler states
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* @param sd Looking for a start delimiter
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* @param src Looking for a source
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* @param dest Looking for a destination
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* @param comd Looking for a command
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* @param read Reading data payload
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* @param cs Calcualting the checksum and returning
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*/
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typedef enum { |
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sd, |
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src, |
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dest, |
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comd, |
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plen, |
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read, |
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cs |
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} state_t; |
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/**
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* @brief Parses a tooltron packet
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*
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* This is a state machine that parses the packet. It uses a software
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* counter to track timeout status. The timeout is not reset unless
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* a fully valid packet is found. It will fail if there is a timeout,
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* crc error, or any error in the packet. All data will be placed in
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* mbuf. Note that mbuf must be able to handle PROGD_PACKET_SIZE
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* bytes.
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*
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* @pre mbuf is PROGD_PACKET_SIZE bytes large
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* @param mbuf Buffer to write the packet data payload to if there is one
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* @param addr The address of the sending node
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* @return the command received or TT_BAD on any error
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*/
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char parse_packet(uint8_t *mbuf, uint8_t *len, uint8_t addr) {
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uint8_t r; // Byte from the network
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uint8_t crc; // Running checksum of the packet
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uint8_t cmd; // The command received
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uint8_t pos; // Position in the message buffer
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uint8_t lim; // Max number of bytes to read into the message buf
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state_t state; // State machine
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uint16_t count; |
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r = 0;
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crc = 0;
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cmd = 0;
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pos = 0;
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lim = 0;
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state = sd; |
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count = 0;
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while (1) { |
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// Wait for the next byte
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while ((rs485_get_byte(&r)) < 0) { |
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if (count >= MAX_TIMEOUT) {
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return TT_BAD;
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} else {
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count++; |
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} |
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} |
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switch (state) {
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case sd:
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if (r == DELIM) {
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state = src; |
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} |
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break;
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case src:
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if (r == DELIM) {
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state = src; |
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} else {
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crc = r; |
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state = dest; |
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} |
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break;
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case dest:
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if (r == DELIM) {
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state = src; |
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} else if (r == addr) { |
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crc ^= r; |
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state = comd; |
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} else {
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state = sd; |
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} |
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break;
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case comd:
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cmd = r; |
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crc ^= r; |
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if (r == DELIM) {
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state = src; |
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} else {
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state = plen; |
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} |
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break;
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case plen:
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lim = r; |
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crc ^= r; |
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*len = r; |
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if (r == 0) { |
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state = cs; |
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} else {
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state = read; |
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} |
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break;
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case read:
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mbuf[pos] = r; |
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crc ^= r; |
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pos++; |
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if (pos == lim) {
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state = cs; |
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} |
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break;
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case cs:
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if (r == crc) {
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if (cmd == TT_RESET) {
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reset(); |
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} |
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return cmd;
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} else {
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return TT_BAD;
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} |
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break;
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default:
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return TT_BAD;
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} |
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} |
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} |
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/**
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* @brief Sends a packet of type cmd onto the network
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* @param cmd The command to send
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* @param addr The address of the sending node
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* @param data Pointer to data
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* @param len Number of bytes to send
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*/
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void send_packet(uint8_t cmd, uint8_t addr, uint8_t* data, uint8_t len) {
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uint8_t i; |
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uint8_t crc = 0;
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rs485_toggle_transmit(RS485_TX_ON); |
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rs485_send_byte(DELIM); |
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rs485_send_byte(addr); |
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rs485_send_byte(SERVER); |
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rs485_send_byte(cmd); |
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rs485_send_byte(len); |
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for (i=0; i < len; i++) { |
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crc ^= data[i]; |
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rs485_send_byte(data[i]); |
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} |
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rs485_send_byte(addr ^ SERVER ^ len ^ cmd ^ crc); |
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rs485_toggle_transmit(RS485_TX_OFF); |
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} |
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