Diff: main.cpp

Revision:

0:f1e54c45ccaf

Child:

1:8064f8b8cf82

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/main.cpp	Fri Mar 12 10:12:32 2010 +0000
@@ -0,0 +1,68 @@
+#include "mbed.h"
+// Super-fast DigitalOut-like class for mbed
+//   by Igor Skochinsky
+
+// usage: FastOut<LED2> led2;
+// then use the same assignment operators as with DigitalOut
+template <PinName pin> class FastOut
+{
+// pin = LPC_GPIO0_BASE + port * 32 + bit
+// port = (pin - LPC_GPIO0_BASE) / 32
+// bit  = (pin - LPC_GPIO0_BASE) % 32
+    
+    // helper function to calculate the GPIO port definition for the pin
+    // we rely on the fact that port structs are 0x20 bytes apart
+    inline LPC_GPIO_TypeDef* portdef() { return (LPC_GPIO_TypeDef*)(LPC_GPIO0_BASE + ((pin - P0_0)/32)*0x20); };
+
+    // helper function to calculate the mask for the pin's bit in the port
+    inline uint32_t mask() { return 1UL<<((pin - LPC_GPIO0_BASE) % 32); };
+
+public:
+    FastOut()
+    {
+        // set FIODIR bit to 1 (output)
+        portdef()->FIODIR |= mask();
+    }
+    void write(int value)
+    { 
+        if ( value )
+            portdef()->FIOSET = mask();
+        else
+            portdef()->FIOCLR = mask();
+    } 
+    int read()
+    {
+        return (portdef()->FIOPIN) & mask() != 0;
+    }
+    FastOut& operator= (int value) { write(value); return *this; };
+    FastOut& operator= (FastOut& rhs) { return write(rhs.read()); };
+    operator int() { return read(); };
+};
+
+DigitalOut led1(LED1);
+FastOut<LED2> led2;
+
+Timer t;
+#define LOOPS 100000000
+int main() {
+    int value = 0;
+    int count = LOOPS;
+    t.start();
+    while ( count -- )
+    {
+        led1.write(value);
+        value = 1-value;
+    }
+    t.stop();
+    printf("DigitalOut: %f seconds (%d ns per iteration).\n", t.read(), t.read_us()/(LOOPS/1000));
+    count = LOOPS;
+    t.reset();
+    t.start();
+    while ( count -- )
+    {
+        led2 = value;
+        value = 1-value;
+    }
+    t.stop();
+    printf("FastOut: %f seconds (%d ns per iteration).\n", t.read(), t.read_us()/(LOOPS/1000));
+}