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lunix-protocol.c
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lunix-protocol.c
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/*
* lunix-protocol.c
*
* This code implements the protocol used by the
* wireless sensor network to report back on the
* measurements of individual sensors.
*
* It receives raw packet data from the Lunix line discipline
* and updates the relevant sensor structures with the
* newly received measured values.
*
* Ioannis Panagopoulos <ioannis@cslab.ece.ntua.gr>
* Vangelis Koukis <vkoukis@cslab.ece.ntua.gr>
*
*/
#include <linux/kernel.h>
#include <asm/byteorder.h>
#include "lunix.h"
#include "lunix-protocol.h"
/*
* Returns an unsigned 16-bit integer in native byte-order from
* two bytes in an XMesh packet, which is always little-endian
*/
static uint16_t uint16_from_packet(unsigned char *p)
{
uint16_t le;
memcpy(&le, p, 2);
return le16_to_cpu(le);
}
/*
* Will display the contents of an incoming XMesh packet
* that have been received so far
*/
static inline void lunix_protocol_show_packet(struct lunix_protocol_state_struct *state)
{
#if LUNIX_DEBUG
int ctr;
debug("Current packet: called, pos = %d, Packet data: { ", state->pos);
for (ctr = 0; ctr < state->pos; ctr++)
printk("0x%02x%s", state->packet[ctr], (ctr == state->pos - 1) ? "" : ", ");
printk(" }\n");
#endif
}
/*
* Receives a complete XMesh packet and updates the node structures if
* the packet contains sensor information. The function ignores other
* types of packets. In future releases check packets with packet[4]
* equal to 0x03, 0xFD for extending this function.
*/
static void lunix_protocol_update_sensors(struct lunix_protocol_state_struct *state, struct lunix_sensor_struct *lunix_sensors)
{
uint16_t batt;
uint16_t temp;
uint16_t light;
uint16_t nodeid;
//debug("WHOLE PACKET\n");
if (0x0B == state->packet[PACKET_SIGNATURE_OFFSET])
{
nodeid = uint16_from_packet(&state->packet[NODE_OFFSET]);
batt = uint16_from_packet(&state->packet[VREF_OFFSET]);
temp = uint16_from_packet(&state->packet[TEMPERATURE_OFFSET]);
light = uint16_from_packet(&state->packet[LIGHT_OFFSET]);
/* FIXME */
//debug ("I have the following raw data from nodeid = %d: { batt, temp, light } = { 0x%04x, 0x%04x, 0x%04x }\n",
// nodeid, batt, temp, light);
if (nodeid > 0 && nodeid <= lunix_sensor_cnt)
lunix_sensor_update(&lunix_sensors[nodeid - 1], batt, temp, light);
else
printk(KERN_WARNING "Node id %d is out of bounds [maximum %d sensors]\n",
nodeid, lunix_sensor_cnt);
}
}
/**********************************************************************************
* PACKET STRUCTURE
* BYTE VALUE MEANING
* 0 0x7E Packet Start byte signature
* 1 0x?? Packet Type
* 2-3 0x?? Destination Address
* 4 0x?? AM Type
* 5 0x?? AM Group
* 6 0x?? Payload length (PL)
* 7-(7 + PL-1) 0x?? PayLoad
* (7 + PL)-(7 + PL + 1) 0x?? CRC
* (7 + PL + 2) 0X7E Packet End byte signature
**********************************************************************************/
/*
* Helper function to quickly set the current state
*/
static inline void set_state(struct lunix_protocol_state_struct *statep, int state, int btr, int br)
{
//debug("switching to state %d, bytes_to_read = %d, bytes_read = %d\n",
// state, btr, br);
statep->state = state;
statep->bytes_to_read = btr;
statep->bytes_read = br;
//lunix_protocol_show_packet(statep);
}
/*
* Initialization of protocol state machine
*/
void lunix_protocol_init(struct lunix_protocol_state_struct *state)
{
state->pos = 0;
state->next_is_special = 0;
set_state(state, SEEKING_START_BYTE, 1, 0);
}
/*
* Crucial function for parsing the input packet according
* to the current state.
*
* struct lunix_protocol_state_struct *state:
* unsigned char *data: the data received
* int length: the amount of bytes received
* int *i: the pointer to the data received is updated when data are
* transferred to the unparsed_packet array
* int use_specials: if 1 special characters are treated acc
*/
static int lunix_protocol_parse_state(struct lunix_protocol_state_struct *state,
const unsigned char *data, int length, int *i, int use_specials)
{
int iter;
//debug("entering, for *i = %d, length = %d, state = %d, btr = %d, br = %d, next_is_special = %d\n",
// *i, length, state->state, state->bytes_to_read, state->bytes_read, state->next_is_special);
iter = 0;
while ((*i < length) && (state->bytes_read < state->bytes_to_read))
{
#if LUNIX_DEBUG
if (++iter == 50) {
debug("OOPS!\n");
return -1;
}
#endif
/* Prevent buffer overflows */
if (state->pos == MAX_PACKET_LEN) {
printk(KERN_ERR "WARNING: state->pos == %d, MAX_PACKET_LEN is %d,"
"packet buffer would overflow!\n", state->pos, MAX_PACKET_LEN);
printk(KERN_ERR "How will I ever resync with the input stream?\n");
state->pos = 0;
return -1;
}
if (1 == use_specials)
{
if (state->next_is_special)
{
if (0x7E == state->next_is_special)
state->packet[state->pos] = data[*i];
if (0x7D == state->next_is_special)
state->packet[state->pos] = data[*i]^0x20;
++state->pos;
++state->bytes_read;
++(*i);
state->next_is_special = 0;
}
else
{
if ((0x7E == data[*i]) || (0x7D == data[*i]))
{
state->next_is_special = data[*i];
++(*i);
} else {
state->packet[state->pos] = data[*i];
++state->pos;
++state->bytes_read;
++(*i);
}
}
}
else
{
state->packet[state->pos] = data[*i];
++state->pos;
++state->bytes_read;
++(*i);
}
}
if (state->bytes_read == state->bytes_to_read) {
//debug("returning 1 from state = %d, btr = %d, br = %d, next_is_special = %d\n",
// state->state, state->bytes_to_read, state->bytes_read, state->next_is_special);
return 1;
}
//debug("returning 0 from state = %d, btr = %d, br = %d, next_is_special = %d\n",
// state->state, state->bytes_to_read, state->bytes_read, state->next_is_special);
return 0;
}
/*
* This function gets called for incoming data
* to update the protocol state machine.
*/
int lunix_protocol_received_buf(struct lunix_protocol_state_struct *state,
const unsigned char *buf, int length)
{
int i;
int payload_length;
i = 0;
if (state->state == SEEKING_START_BYTE)
if (lunix_protocol_parse_state(state, buf, length, &i, 0) == 1)
set_state(state, SEEKING_PACKET_TYPE, 1, 0);
if (state->state == SEEKING_PACKET_TYPE)
if (lunix_protocol_parse_state(state, buf, length, &i, 0) == 1)
set_state(state, SEEKING_DESTINATION_ADDRESS, 2, 0);
if (state->state == SEEKING_DESTINATION_ADDRESS)
if (lunix_protocol_parse_state(state, buf, length, &i, 1) == 1)
set_state(state, SEEKING_AM_TYPE, 1, 0);
if (state->state == SEEKING_AM_TYPE)
if (lunix_protocol_parse_state(state, buf, length, &i, 1) == 1)
set_state(state, SEEKING_AM_GROUP, 1, 0);
if (state->state == SEEKING_AM_GROUP)
if (lunix_protocol_parse_state(state, buf, length, &i, 1) == 1)
set_state(state, SEEKING_PAYLOAD_LENGTH, 1, 0);
if (state->state == SEEKING_PAYLOAD_LENGTH)
if (lunix_protocol_parse_state(state, buf, length, &i, 1) == 1) {
payload_length = state->packet[state->pos - 1];
set_state(state, SEEKING_PAYLOAD, payload_length, 0);
}
if (state->state == SEEKING_PAYLOAD)
if (lunix_protocol_parse_state(state, buf, length, &i, 1) == 1)
set_state(state, SEEKING_CRC, 2, 0);
if (state->state == SEEKING_CRC)
if (lunix_protocol_parse_state(state, buf, length, &i, 1) == 1)
set_state(state, SEEKING_END_BYTE, 1, 0);
if (state->state == SEEKING_END_BYTE)
if (lunix_protocol_parse_state(state, buf, length, &i, 0) == 1) {
//debug("An XMesh packet has been received, updating sensors\n");
lunix_protocol_update_sensors(state, lunix_sensors);
state->pos = 0;
state->next_is_special = 0;
set_state(state, SEEKING_START_BYTE, 1, 0);
}
//debug("leaving\n");
return 0;
}