forked from luon/wordclock
100 lines
2.5 KiB
Plaintext
100 lines
2.5 KiB
Plaintext
/**
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* This is a very small example that shows how to use
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* protothreads. The program consists of two protothreads that wait
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* for each other to toggle a variable.
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*/
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/* We must always include pt.h in our protothreads code. */
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#include "pt.h"
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/* Two flags that the two protothread functions use. */
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static int protothread1_flag, protothread2_flag;
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/* protothread state variables, one for each ptorothread. */
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static struct pt pt1, pt2;
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/**
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* The first protothread function. A protothread function must always
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* return an integer, but must never explicitly return - returning is
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* performed inside the protothread statements.
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*
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* The protothread function is driven by the main loop further down in
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* the code.
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*/
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static int protothread1(struct pt *pt)
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{
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/* A protothread function must begin with PT_BEGIN() which takes a
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pointer to a struct pt. */
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PT_BEGIN(pt);
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/* We loop forever here. */
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while(1) {
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/* Wait until the other protothread has set its flag. */
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PT_WAIT_UNTIL(pt, protothread2_flag != 0);
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Serial.println("Protothread 1 running");
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/* We then reset the other protothread's flag, and set our own
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flag so that the other protothread can run. */
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protothread2_flag = 0;
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protothread1_flag = 1;
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/* And we loop. */
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}
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/* All protothread functions must end with PT_END() which takes a
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pointer to a struct pt. */
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PT_END(pt);
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}
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/**
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* The second protothread function.
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* This one is almost the same as the first one.
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*/
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static int protothread2(struct pt *pt)
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{
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PT_BEGIN(pt);
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while(1) {
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/* Let the other protothread run. */
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protothread2_flag = 1;
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/* Wait until the other protothread has set its flag. */
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PT_WAIT_UNTIL(pt, protothread1_flag != 0);
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Serial.println("Protothread 2 running");
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/* We then reset the other protothread's flag. */
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protothread1_flag = 0;
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/* And we loop. */
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}
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PT_END(pt);
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}
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/**
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* setup() is where the protothreads are initialized.
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* The state variables pt1 and pt2 holdthe state of the two protothreads.
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*/
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void setup()
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{
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/* Initialize the protothread state variables with PT_INIT(). */
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PT_INIT(&pt1);
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PT_INIT(&pt2);
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Serial.begin(9600);
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}
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/**
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* Finally, we have the main loop.
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* This is where the protothreads are scheduled.
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*/
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void loop()
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{
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/*
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* We schedule the two protothreads by repeatedly calling their
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* protothread functions and passing a pointer to the protothread
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* state variables as arguments.
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*/
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protothread1(&pt1);
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protothread2(&pt2);
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}
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