rp2040

commit 62c0baf87b41ca67319400b478ac5bb441f4232b
parent d87427e253fed2f078fe90e9105b4a4783c5981d
Author: Matsuda Kenji <info@mtkn.jp>
Date:   Thu, 29 Feb 2024 08:57:13 +0900

move to c

Diffstat:
M
ex3/main.c
 | 
12
+++++++++---
M
ex3/start.s
 | 
69
+++++++++++++++++++++++++++++++++------------------------------------

2 files changed, 42 insertions(+), 39 deletions(-)
diff --git a/ex3/main.c b/ex3/main.c
@@ -1,12 +1,18 @@
-void puts(char *);
+int puts(char *);
+void set_alarm(unsigned int);
 
 int
 main(void) {
-	puts("C file\n");
+	puts("C file");
 	return 0;
 }
 
 void
 isr_svcall(void) {
-	puts("svcall\n");
+	puts("svcall");
+}
+
+void
+isr_alarm(void) {
+	set_alarm(0x20000);
 }
diff --git a/ex3/start.s b/ex3/start.s
@@ -114,13 +114,9 @@ wait_vco:
 	mov r0, #1
 	str r0, [r3, r1] // M0PLUS: NVIC_ISER
 
-	// setup timer
-	ldr r3, timer_base
-	// enable alarm_0 interrupt
-	mov r0, #1 // ALARM_0
-	str r0, [r3, #0x38] // TIMER: INTE
 	// set timer
-	ldr r0, =0x20000 // 
+	bl init_timer
+	ldr r0, =0x20000
 	bl set_alarm
 
 	bl main
@@ -134,35 +130,10 @@ loop:
 
 // functions
 
-isr_systick:
-	push {lr}
-	mov r0, #'\r'
-	bl putbyte
-	ldr r1, =0x20000000
-	ldr r0, [r1, #0]
-	add r0, #1
-	str r0, [r1, #0]
-	bl printh
-	mov r0, #'\n'
-	bl putbyte
-	pop {pc}
-
-isr_alarm:
-	push {lr}
-	// clear interrupt
-	ldr r3, timer_base
-	ldr r2, atomic_clr
-	mov r1, #0x34
-	add r1, r1, r2
-	mov r0, #1
-	str r0, [r3, r1] // TIMER: INTR
-	// reset timer
-	ldr r0, =0x20000 // 1 sec
-	bl set_alarm
-	pop {pc}
-
-	// unreset deasserts reset bit of subsystems specified by r0
+	// void unreset(unsigned int sub_systems);
+	// unreset deasserts reset bit of subsystems specified by sub_systems.
 	// and wait for them complete unreset.
+	.global unreset
 unreset:
 	ldr r3, resets_base
 	ldr r1, atomic_clr
@@ -173,9 +144,30 @@ unreset_chk:
 	bne unreset_chk
 	bx lr
 
-	// set_alarm sets alarm_0 to fire after r0 us.
+	// void init_timer(void);
+	// Init_timer enables alarm_0 and its interrupt.
+	// It assumes that the timer is out of reset.
+	.global init_timer
+init_timer:
+	ldr r3, timer_base
+	// enable alarm_0 interrupt
+	mov r0, #1 // ALARM_0
+	str r0, [r3, #0x38] // TIMER: INTE
+	bx lr
+
+	// void set_alarm(unsigned int us);
+	// Set_alarm clears timer interrupt and then sets alarm_0 to fire,
+	// after us micro seconds.
+	.global set_alarm
 set_alarm:
 	ldr r3, timer_base
+	// clear interrupt
+	ldr r2, atomic_clr
+	mov r1, #0x34
+	add r1, r1, r2
+	mov r2, #1
+	str r2, [r3, r1] // TIMER: INTR
+	// set alarm0
 	ldr r1, [r3, #0x28] // TIMER: TIMERAWL
 	add r0, r1
 	str r0, [r3, #0x10] // TIMER: ALARM0
@@ -204,7 +196,9 @@ alpha:
 	bge printh_loop
 	pop {r4, r5, r6, r7, pc}
 
-	// puts prints null terminated string starting at r0.
+	// Puts prints null terminated string starting at r0 and a trailing new line
+	// to uart0.
+	// It returns a nonnegative number on success.
 	.global puts
 puts:
 	push {r4, lr}
@@ -217,6 +211,9 @@ puts_loop:
 	add r4, #1
 	b puts_loop
 puts_end:
+	mov r0, #'\n'
+	bl putbyte
+	mov r0, #0 // return value
 	pop {r4, pc}
 
 putbyte: