90 lines
2.5 KiB
C
90 lines
2.5 KiB
C
/*
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* This file contains an example of how a Contiki program looks.
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*
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* The program opens a UDP broadcast connection and sends one packet
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* every second.
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*/
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#include "contiki.h"
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#include "contiki-net.h"
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/*
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* All Contiki programs must have a process, and we declare it here.
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*/
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PROCESS(example_program_process, "Example process");
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/*
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* To make the program send a packet once every second, we use an
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* event timer (etimer).
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*/
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static struct etimer timer;
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/*---------------------------------------------------------------------------*/
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/*
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* Here we implement the process. The process is run whenever an event
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* occurs, and the parameters "ev" and "data" will we set to the event
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* type and any data that may be passed along with the event.
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*/
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PROCESS_THREAD(example_program_process, ev, data)
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{
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/*
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* Declare the UDP connection. Note that this *MUST* be declared
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* static, or otherwise the contents may be destroyed. The reason
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* for this is that the process runs as a protothread, and
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* protothreads do not support stack variables.
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*/
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static struct uip_udp_conn *c;
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/*
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* A process thread starts with PROCESS_BEGIN() and ends with
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* PROCESS_END().
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*/
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PROCESS_BEGIN();
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/*
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* We create the UDP connection to port 4321. We don't want to
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* attach any special data to the connection, so we pass it a NULL
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* parameter.
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*/
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c = udp_broadcast_new(UIP_HTONS(4321), NULL);
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/*
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* Loop for ever.
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*/
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while(1) {
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/*
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* We set a timer that wakes us up once every second.
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*/
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etimer_set(&timer, CLOCK_SECOND);
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PROCESS_WAIT_EVENT_UNTIL(etimer_expired(&timer));
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/*
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* Now, this is a the tricky bit: in order for us to send a UDP
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* packet, we must call upon the uIP TCP/IP stack process to call
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* us. (uIP works under the Hollywood principle: "Don't call us,
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* we'll call you".) We use the function tcpip_poll_udp() to tell
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* uIP to call us, and then we wait for the uIP event to come.
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*/
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tcpip_poll_udp(c);
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PROCESS_WAIT_EVENT_UNTIL(ev == tcpip_event);
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/*
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* We can now send our packet.
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*/
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uip_send("Hello", 5);
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/*
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* We're done now, so we'll just loop again.
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*/
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}
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/*
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* The process ends here. Even though our program sits is a while(1)
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* loop, we must put the PROCESS_END() at the end of the process, or
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* else the program won't compile.
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*/
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PROCESS_END();
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}
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/*---------------------------------------------------------------------------*/
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