1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
|
.syntax unified
.cpu cortex-m0plus
.thumb
.equ RESETS_BASE, 0x4000c000
.equ RESET_OFST, 0x0
.equ RESET_DONE_OFST, 0x8
.equ IO_BANK0_BASE, 0x40014000
.equ GPIO0_CTRL_OFST, 0x04
.equ GPIO1_CTRL_OFST, 0x0c
.equ UART0_BASE, 0x40034000
.equ UARTDR_OFST, 0x00
.equ UARTFR_OFST, 0x18
.equ UARTIBRD_OFST, 0x24
.equ UARTFBRD_OFST, 0x28
.equ UARTLCR_H_OFST, 0x2c
.equ UARTCR_OFST, 0x30
.equ ATOMIC_SET, 0x2000
.equ ATOMIC_CLEAR, 0x3000
.type setup_uart, %function
.global setup_uart
setup_uart:
// Deassert reset
ldr r1, =(RESETS_BASE + ATOMIC_CLEAR)
movs r0, 0b1 // UART0
lsls r0, 22
str r0, [r1, RESET_OFST]
ldr r1, =RESETS_BASE
1:
ldr r2, [r1, RESET_DONE_OFST]
tst r2, r0
beq 1b
// Configure and enable
ldr r1, =UART0_BASE
movs r0, 6
str r0, [r1, UARTIBRD_OFST]
movs r0, 33
str r0, [r1, UARTFBRD_OFST]
movs r0, 0b111 << 4 // 0b11 = word len 8 bits, 0b1 = FIFO enabled
str r0, [r1, UARTLCR_H_OFST]
ldr r1, =(UART0_BASE + ATOMIC_SET)
movs r0, 0b1 // UART enable
str r0, [r1, UARTCR_OFST]
// Configure GPIO 0 and 1 as TX and RX
ldr r1, =IO_BANK0_BASE
movs r0, 2 // UART function
str r0, [r1, GPIO0_CTRL_OFST]
str r0, [r1, GPIO1_CTRL_OFST]
bx lr
.type uart_send, %function
.global uart_send
uart_send:
ldr r1, =UART0_BASE
movs r3, 0b1 << 5 // TX FIFO full
1:
ldr r2, [r1, UARTFR_OFST]
tst r2, r3
bne 1b
strb r0, [r1, UARTDR_OFST]
bx lr
.type uart_recv, %function
.global uart_recv
uart_recv:
ldr r1, =UART0_BASE
movs r3, 0b1 << 4 // RX FIFO empty
1:
ldr r2, [r1, UARTFR_OFST]
tst r2, r3
bne 1b
ldrb r0, [r1, UARTDR_OFST]
bx lr
.type send_hex, %function
.global send_hex
send_hex:
push {lr}
movs r4, r0
movs r0, '0
bl uart_send
movs r0, 'x
bl uart_send
movs r5, 8 // eight nibbles in a word
0:
movs r0, 28 // rotate left 4
rors r4, r0
movs r0, 0xF // lowest nibble mask
ands r0, r4
cmp r0, 0x9 // number or letter?
bhi 1f
adds r0, '0
b 2f
1:
adds r0, 'A - 0xA
2:
bl uart_send
subs r5, 1
bne 0b
movs r0, '\r
bl uart_send
movs r0, '\n
bl uart_send
pop {pc}
|
