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| 1 | #include <packet.h> |
|---|---|
| 2 | |
| 3 | |
| 4 | /**
|
| 5 | * @brief Packet handler states |
| 6 | * @param sd Looking for a start delimiter |
| 7 | * @param src Looking for a source |
| 8 | * @param dest Looking for a destination |
| 9 | * @param comd Looking for a command |
| 10 | * @param read Reading data payload |
| 11 | * @param cs Calcualting the checksum and returning |
| 12 | */ |
| 13 | typedef enum { |
| 14 | sd, |
| 15 | src, |
| 16 | dest, |
| 17 | comd, |
| 18 | read, |
| 19 | cs |
| 20 | } state_t; |
| 21 | |
| 22 | /**
|
| 23 | * @brief Parses a tooltron packet |
| 24 | * |
| 25 | * This is a state machine that parses the packet. It uses a software |
| 26 | * counter to track timeout status. The timeout is not reset unless |
| 27 | * a fully valid packet is found. It will fail if there is a timeout, |
| 28 | * crc error, or any error in the packet. All data will be placed in |
| 29 | * mbuf. Note that mbuf must be able to handle PROGD_PACKET_SIZE |
| 30 | * bytes. |
| 31 | * |
| 32 | * @pre mbuf is PROGD_PACKET_SIZE bytes large |
| 33 | * @param mbuf Buffer to write the packet data payload to if there is one |
| 34 | * @param addr The address of the sending node |
| 35 | * @return the command received or TT_BAD on any error |
| 36 | */ |
| 37 | char parse_packet(uint8_t *mbuf, uint8_t addr) {
|
| 38 | uint8_t r; // Byte from the network
|
| 39 | uint8_t crc; // Running checksum of the packet
|
| 40 | uint8_t cmd; // The command received
|
| 41 | uint8_t pos; // Position in the message buffer
|
| 42 | uint8_t lim; // Max number of bytes to read into the message buf
|
| 43 | state_t state; // State machine
|
| 44 | uint16_t count; |
| 45 | |
| 46 | r = 0;
|
| 47 | crc = 0;
|
| 48 | cmd = 0;
|
| 49 | pos = 0;
|
| 50 | lim = 0;
|
| 51 | state = sd; |
| 52 | count = 0;
|
| 53 | |
| 54 | while (1) { |
| 55 | // Wait for the next byte
|
| 56 | while ((rs485_get_byte(&r)) < 0) { |
| 57 | if (count >= MAX_TIMEOUT) {
|
| 58 | return TT_BAD;
|
| 59 | } else {
|
| 60 | count++; |
| 61 | } |
| 62 | } |
| 63 | |
| 64 | switch (state) {
|
| 65 | case sd: |
| 66 | if (r == DELIM) {
|
| 67 | state = src; |
| 68 | } |
| 69 | break;
|
| 70 | |
| 71 | case src: |
| 72 | if (r == DELIM) {
|
| 73 | state = src; |
| 74 | } else {
|
| 75 | crc = r; |
| 76 | state = dest; |
| 77 | } |
| 78 | break;
|
| 79 | |
| 80 | case dest: |
| 81 | if (r == DELIM) {
|
| 82 | state = src; |
| 83 | } else if (r == addr) { |
| 84 | crc ^= r; |
| 85 | state = comd; |
| 86 | } else {
|
| 87 | state = sd; |
| 88 | } |
| 89 | break;
|
| 90 | |
| 91 | case comd: |
| 92 | cmd = r; |
| 93 | crc ^= r; |
| 94 | |
| 95 | if (r == DELIM) {
|
| 96 | state = src; |
| 97 | } else if (r == TT_PROGM) { |
| 98 | lim = PROGM_PACKET_SIZE; |
| 99 | state = read; |
| 100 | } else if (r == TT_PROGD) { |
| 101 | lim = PROGD_PACKET_SIZE; |
| 102 | state = read; |
| 103 | } else {
|
| 104 | state = cs; |
| 105 | } |
| 106 | break;
|
| 107 | |
| 108 | case read: |
| 109 | mbuf[pos] = r; |
| 110 | crc ^= r; |
| 111 | pos++; |
| 112 | |
| 113 | if (pos == lim) {
|
| 114 | state = cs; |
| 115 | } |
| 116 | |
| 117 | break;
|
| 118 | |
| 119 | case cs: |
| 120 | if (r == crc) {
|
| 121 | if (cmd == TT_RESET) {
|
| 122 | reset(); |
| 123 | } |
| 124 | return cmd;
|
| 125 | } else {
|
| 126 | return TT_BAD;
|
| 127 | } |
| 128 | |
| 129 | break;
|
| 130 | |
| 131 | default:
|
| 132 | return TT_BAD;
|
| 133 | } |
| 134 | } |
| 135 | } |
| 136 | |
| 137 | /**
|
| 138 | * @brief Sends a packet of type cmd onto the network |
| 139 | * @param cmd The command to send |
| 140 | * @param addr The address of the sending node |
| 141 | */ |
| 142 | void send_packet(uint8_t cmd, uint8_t addr) {
|
| 143 | rs485_send_byte(DELIM); |
| 144 | rs485_send_byte(addr); |
| 145 | rs485_send_byte(SERVER); |
| 146 | rs485_send_byte(cmd); |
| 147 | rs485_send_byte(addr ^ SERVER ^ cmd); |
| 148 | } |
| 149 |