new feature "HAVE_UNPRECISEWAIT" for save some flash

[pub/USBaspLoader.git] / firmware / main.c

diff --git a/firmware/main.c b/firmware/main.c
index fda58a2..8012e20 100644 (file)
--- a/firmware/main.c
+++ b/firmware/main.c
@@ -386,10 +386,33 @@ uchar   i;
 
 static void initForUsbConnectivity(void)
 {
+#if HAVE_UNPRECISEWAIT
+    /* (0.25s*F_CPU)/(4 cycles per loop) ~ (65536*waitloopcnt)
+     * F_CPU/(16*65536) ~ waitloopcnt
+     * F_CPU / 1048576 ~ waitloopcnt
+     */
+    uint8_t waitloopcnt = 1 + (F_CPU/1048576);
+#endif
     usbInit();
     /* enforce USB re-enumerate: */
     usbDeviceDisconnect();  /* do this while interrupts are disabled */
+#if HAVE_UNPRECISEWAIT
+    asm volatile (
+      /*we really don't care what value Z has...
+       * ...if we loop 65536/F_CPU more or less...
+       * ...unimportant - just save some opcodes
+       */
+"initForUsbConnectivity_sleeploop:                     \n\t"
+      "sbiw    r30,    1                               \n\t"
+      "sbci    %0,     0                               \n\t"
+      "brne    initForUsbConnectivity_sleeploop        \n\t"
+      : "+d" (waitloopcnt)
+      :
+      : "r30","r31"
+    );
+#else
     _delay_ms(260);         /* fake USB disconnect for > 250 ms */
+#endif
     usbDeviceConnect();
     sei();
 }