From 606ac5c2f84b47c032190d780335759788d5af79 Mon Sep 17 00:00:00 2001
From: Jeff Wang <jeff.wang@utexas.edu>
Date: Thu, 21 Mar 2019 21:03:35 -0400
Subject: [PATCH] optimize delays for better accuracy

---
 src/main.c  | 33 ++++++++++++++++++++++++---------
 src/utils.c | 46 ++++++++++++++++++++++++++++++++--------------
 src/utils.h |  3 +--
 3 files changed, 57 insertions(+), 25 deletions(-)

diff --git a/src/main.c b/src/main.c
index 2948e83..677c400 100644
--- a/src/main.c
+++ b/src/main.c
@@ -8,7 +8,7 @@
 #include "key.h"
 #include "utils.h"
 
-#define FOSC 11059200
+#define FOSC 11583000
 
 
 static const char KEY_MAP[20] = {
@@ -46,19 +46,34 @@ void timer0_isr() __interrupt 1 __using 1
 		INCR_NEW_KEY_I(new_key_write_i);
 		new_key_empty = 0;
 	}
+
+	//track time
+	count++;
+	if (count == 200){
+		count = 0;
+		SecCount++;
+		if (SecCount == 60){
+			SecCount = 0;
+			min_count++;
+			if (min_count == 60){
+				min_count = 0;
+				hour_count++;
+			}
+		}
+	}
 }
 
 
-// Call timer0_isr() 10000/sec: 0.0001 sec
-// Initialize the timer count so that it overflows after 0.0001 sec
-// THTL = 0x10000 - FOSC / 12 / 10000 = 0x10000 - 92.16 = 65444 = 0xFFA4
-void Timer0Init(void)		//100us @ 11.0592MHz
+// Call timer0_isr() 200/sec: 5 ms period
+// Initialize the timer count so that it overflows after 0.01 sec
+// THTL = 0x10000 - FOSC / 200 = 0x10000 - 115830 = 7621 = 0x1DC5
+void Timer0Init(void)
 {
-	// TMOD = 0;	// default: 16-bit auto-reload
-	// AUXR = 0;	// default: traditional 8051 timer frequency of FOSC / 12
+	// TMOD = 0;    // default: 16-bit auto-reload
+	AUXR |= 0x80;   // use undivided SYSclk for timer0
 	// Initial values of TL0 and TH0 are stored in hidden reload registers: RL_TL0 and RL_TH0
-	TL0 = 0xA4;		// Initial timer value
-	TH0 = 0xFF;		// Initial timer value
+	TL0 = 0xC5;		// Initial timer value
+	TH0 = 0x1D;		// Initial timer value
 	TF0 = 0;		// Clear overflow flag
 	TR0 = 1;		// Timer0 start run
 	ET0 = 1;		// Enable timer0 interrupt
diff --git a/src/utils.c b/src/utils.c
index 323c6aa..4542545 100644
--- a/src/utils.c
+++ b/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)
diff --git a/src/utils.h b/src/utils.h
index 6264455..c2c8808 100644
--- a/src/utils.h
+++ b/src/utils.h
@@ -11,8 +11,7 @@
 
 void _delay_ms(uint8_t ms);
 
-//TODO
-#define _delay_us(x) _delay_ms(1)
+void _delay_us(uint8_t us);
 
 char* u32str(uint32_t x, char* buf, uint8_t base);