make PWM duty cycle change more smoothly

diff --git a/msp430/main.c b/msp430/main.c
index 03786aa4b5cb1ab5383644151f2d92310d73eb56..6b075ad91d6b9753f86cb258216d88227842d174 100644 (file)
--- a/msp430/main.c
+++ b/msp430/main.c
@@ -24,6 +24,14 @@ enum {ev_btn1 = 0, ev_btn2, ev_pir1, ev_pir2, ev_tmr, ev_adc, ev_MAX};
 # define BIT_BTN2 0
 #endif
 
+static int expon2(int duty)
+{
+       int shift = duty>>1;
+       int comp = 1<<shift;
+       int extra = (duty & 1) ? comp>>1 : 0;
+       return (duty ? comp|extra : 0);
+}
+
 int main(void)
 {
        int Duty_Cycle = 0;
@@ -153,7 +161,7 @@ int main(void)
                                if (!Time_Indicate)
                                        P1OUT &= ~(BIT_RL|BIT_GL); // LEDs off
                        }
-                       if (Time_Count++ > 20) {
+                       if (Time_Count++ > 10) {
                                Time_Count = 0;
                                if (Time_Left)
                                        Time_Left--;
@@ -161,8 +169,8 @@ int main(void)
                                        Increment = -1;
                        }
                        if (Increment > 0) {
-                               if (++Duty_Cycle >= PWM_ORDER) {
-                                       Duty_Cycle = PWM_ORDER;
+                               if (++Duty_Cycle >= (PWM_ORDER<<1)) {
+                                       Duty_Cycle = PWM_ORDER<<1;
                                        Increment = 0;
                                }
                        } else if (Increment < 0) {
@@ -172,10 +180,8 @@ int main(void)
                                }
                        } else
                                continue;
-                       if (Duty_Cycle)
-                               TA0CCR2 = 1 << (Duty_Cycle - 1);
-                       else
-                               TA0CCR2 = 0;
+
+                       TA0CCR2 = expon2(Duty_Cycle);
                }
                __bis_SR_register(LPM0_bits | GIE);
                __no_operation();