optimize delays for better accuracy

src/utils.c

@@ -2,20 +2,38 @@
 
 void _delay_ms(uint8_t ms)
 {
-    // delay function, tuned for 11.092 MHz clock
-    // optimized to assembler
-    ms; // keep compiler from complaining?
-    __asm;
-        ; dpl contains ms param value
-    delay$:
-        mov	b, #8   ; i
-    outer$:
-        mov	a, #243    ; j
-    inner$:
-        djnz acc, inner$
-        djnz b, outer$
-        djnz dpl, delay$
-    __endasm;
+	// delay function, tuned for 11.583 MHz clock
+	// optimized to assembler
+	ms; // keep compiler from complaining
+	__asm;
+		; dpl contains ms param value
+	ms_delay$:
+		mov	b, #10   ; i, 2 clocks
+	ms_outer$:
+		mov	a, #230    ; j, 2 clocks
+	ms_inner$:
+		djnz acc, ms_inner$  ;4 clocks
+		djnz b, ms_outer$    ;4 clocks
+		djnz dpl, ms_delay$  ;4 clocks
+	__endasm;
+}
+
+void _delay_us(uint8_t us)
+{
+	// delay function, tuned for 11.583 MHz clock
+	// optimized to assembler
+	us; // keep compiler from complaining
+	__asm;
+		; dpl contains us param value
+	us_delay$:
+		nop
+		nop
+		nop
+		nop
+		nop
+		nop
+		djnz dpl, us_delay$
+	__endasm;
 }
 
 char* u32str(uint32_t x, char* buf, uint8_t base)