Revision 0:a2eb037fbb76, committed 2010-09-14

Comitter:

roberto_b

Date:

Tue Sep 14 20:38:26 2010 +0000

Commit message:

Changed in this revision

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/Semaphore.h	Tue Sep 14 20:38:26 2010 +0000
@@ -0,0 +1,34 @@
+//  Copyright (C) 2010 Robert M. Bouwens
+
+#ifndef _SEMAPHORE_H_
+#define _SEMAPHORE_H_
+
+/*
+ * http://mbed.org/forum/mbed/topic/181/#comment-799
+ */
+
+class Semaphore {
+public:
+    Semaphore(): s(SemFree) {};
+
+    bool try_enter() {
+        int oldval = __ldrex(&s);
+        if (oldval == SemTaken) {
+            __clrex();
+            return false;
+        }
+        s = SemTaken;
+        __clrex();
+        return SemTaken == s;
+    };
+
+    void release() {
+        s = SemFree;
+    };
+
+private:
+    enum { SemFree = 1, SemTaken = 2 };
+    volatile int s;
+};
+
+#endif
\ No newline at end of file

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/main.cpp	Tue Sep 14 20:38:26 2010 +0000
@@ -0,0 +1,106 @@
+/**
+ * Test program for a bug. (http://mbed.org/forum/bugs-suggestions/topic/1074/)
+ *
+ * Copyright (C) 2010 Shinichiro Nakamura (CuBeatSystems)
+ * http://shinta.main.jp/
+ */
+
+#include "mbed.h"
+#include "Semaphore.h"
+
+Serial ser(USBTX, USBRX);
+
+DigitalOut interrupt_data_led(LED1);
+DigitalOut dataled(LED2);
+DigitalOut data_locked_led(LED3);
+DigitalOut no_data_led(LED4);
+
+Semaphore sem;
+
+volatile char shared_resource = 'a';   // This is a shared resource for example.
+
+#define LOCK() sem.try_enter()
+#define UNLOCK() sem.release()
+
+void toggle_led( DigitalOut &led) {
+    if ( 1 == led)
+        led = 0;
+    else
+        led = 1;
+}
+
+char* my_itoa(int val, int base) {
+    static char buf[12] = {0};
+
+    int i = 10;
+    if ( 0 != val) {
+        for (; val && i ; --i, val /= base)
+            buf[i] = "0123456789abcdef"[val % base];
+        return &buf[i+1];
+    } else {
+        buf[0] = '0';
+        buf[1] = '0';
+        return &buf[0];
+    }
+}
+
+void waitBeforeSend(char ch) {
+    while ( 0 == ser.writeable()) {
+        wait_ms(1);
+    }
+    ser.putc( ch );
+    toggle_led(dataled);
+}
+
+
+/**
+ * A call back function for serial interrupt.
+ */
+void func_serial_interrupt(void) {
+    toggle_led(interrupt_data_led);
+    if (LOCK()) {
+        shared_resource = ser.getc();
+        UNLOCK();
+    } else {
+        toggle_led(no_data_led);
+    }
+}
+
+/**
+ * Entry point.
+ */
+int main() {
+    int i = 0;
+    char *out = "my semaphore test program\r\n";
+    ser.attach(&func_serial_interrupt);
+    char *ptr = out;
+    while ( *ptr != 0 ) {
+        waitBeforeSend(*ptr);
+        ptr++;
+    }
+
+    while (1) {
+        /*
+         * Hung up serial communication if you hit keys on console for Serial.
+         */
+        if (LOCK()) {
+            ptr = my_itoa(shared_resource, 16);
+            UNLOCK();
+            while ( *ptr != 0 ) {
+                waitBeforeSend(*ptr);
+                ptr++;
+            }
+            i++;
+            i %= 20;
+            if (!i) {
+                waitBeforeSend('\r');
+                waitBeforeSend('\n');
+            } else {
+                waitBeforeSend(' ');
+            }
+        } else {
+            toggle_led(data_locked_led);
+        }
+        wait_ms(100);
+    }
+}

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mbed.bld	Tue Sep 14 20:38:26 2010 +0000
@@ -0,0 +1,1 @@
+http://mbed.org/users/mbed_official/code/mbed/builds/e2ac27c8e93e