140 lines
4.2 KiB
C
140 lines
4.2 KiB
C
/*
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* This is an example of how to write a network device driver ("packet
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* driver") for Contiki. A packet driver is a regular Contiki process
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* that does two things:
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* # Checks for incoming packets and delivers those to the TCP/IP stack
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* # Provides an output function that transmits packets
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*
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* The output function is registered with the Contiki TCP/IP stack,
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* whereas incoming packets must be checked inside a Contiki process.
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* We use the same process for checking for incoming packets and for
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* registering the output function.
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*/
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/*
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* We include the "contiki-net.h" file to get all the network functions.
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*/
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#include "contiki-net.h"
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/*---------------------------------------------------------------------------*/
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/*
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* We declare the process that we use to register with the TCP/IP stack,
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* and to check for incoming packets.
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*/
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PROCESS(example_packet_driver_process, "Example packet driver process");
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/*---------------------------------------------------------------------------*/
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/*
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* Next, we define the function that transmits packets. This function
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* is called from the TCP/IP stack when a packet is to be transmitted.
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* The packet is located in the uip_buf[] buffer, and the length of the
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* packet is in the uip_len variable.
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*/
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u8_t
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example_packet_driver_output(void)
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{
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let_the_hardware_send_the_packet(uip_buf, uip_len);
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/*
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* A network device driver returns always zero.
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*/
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return 0;
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}
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/*---------------------------------------------------------------------------*/
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/*
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* This is the poll handler function in the process below. This poll
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* handler function checks for incoming packets and delivers them to
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* the TCP/IP stack.
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*/
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static void
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pollhandler(void)
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{
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/*
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* We assume that we have some hardware device that notifies us when
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* a new packet has arrived. We also assume that we have a function
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* that pulls out the new packet (here called
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* check_and_copy_packet()) and puts it in the uip_buf[] buffer. The
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* function returns the length of the incoming packet, and we store
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* it in the global uip_len variable. If the packet is longer than
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* zero bytes, we hand it over to the TCP/IP stack.
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*/
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uip_len = check_and_copy_packet();
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/*
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* The function tcpip_input() delivers the packet in the uip_buf[]
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* buffer to the TCP/IP stack.
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*/
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if(uip_len > 0) {
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tcpip_input();
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}
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/*
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* Now we'll make sure that the poll handler is executed repeatedly.
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* We do this by calling process_poll() with this process as its
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* argument.
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*
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* In many cases, the hardware will cause an interrupt to be executed
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* when a new packet arrives. For such hardware devices, the interrupt
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* handler calls process_poll() (which is safe to use in an interrupt
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* context) instead.
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*/
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process_poll(&example_packet_driver_process);
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}
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/*---------------------------------------------------------------------------*/
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/*
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* Finally, we define the process that does the work.
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*/
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PROCESS_THREAD(example_packet_driver_process, ev, data)
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{
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/*
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* This process has a poll handler, so we declare it here. Note that
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* the PROCESS_POLLHANDLER() macro must come before the PROCESS_BEGIN()
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* macro.
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*/
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PROCESS_POLLHANDLER(pollhandler());
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/*
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* This process has an exit handler, so we declare it here. Note that
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* the PROCESS_EXITHANDLER() macro must come before the PROCESS_BEGIN()
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* macro.
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*/
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PROCESS_EXITHANDLER(exithandler());
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/*
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* The process begins here.
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*/
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PROCESS_BEGIN();
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/*
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* We start with initializing the hardware.
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*/
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initialize_the_hardware();
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/*
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* Register the driver. This will cause any previously registered driver
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* to be ignored by the TCP/IP stack.
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*/
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tcpip_set_outputfunc(example_packet_driver_output);
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/*
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* Now we'll make sure that the poll handler is executed initially. We do
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* this by calling process_poll() with this process as its argument.
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*/
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process_poll(&example_packet_driver_process);
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/*
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* And we wait for the process to exit.
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*/
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PROCESS_WAIT_EVENT_UNTIL(ev == PROCESS_EVENT_EXIT);
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/*
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* Now we shutdown the hardware.
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*/
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shutdown_the_hardware();
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/*
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* Here ends the process.
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*/
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PROCESS_END();
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}
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/*---------------------------------------------------------------------------*/
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