-
Notifications
You must be signed in to change notification settings - Fork 0
/
uplow.1.c
113 lines (93 loc) · 3.3 KB
/
uplow.1.c
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
/* uplow.1.c -- uptime lower layer
** Copyright (c) 2020 Renaud Fivet
**
** uptime = seconds elapsed since boot
** SysClck 8MHz HSI based, baudrate 9600, Busy wait transmission
** user LED toggled every second
** SysTick interrupt every second
*/
#define SYSTICK ((volatile long *) 0xE000E010)
#define SYSTICK_CSR SYSTICK[ 0]
#define SYSTICK_RVR SYSTICK[ 1]
#define SYSTICK_CVR SYSTICK[ 2]
#define CAT( a, b) a##b
#define HEXA( a) CAT( 0x, a)
#define RCC ((volatile long *) 0x40021000)
#define RCC_AHBENR RCC[ 5]
#define RCC_AHBENR_IOP( h) (1 << (17 + HEXA( h) - 0xA))
#define RCC_APB2ENR RCC[ 6]
#define RCC_APB2ENR_USART1EN 0x00004000 /* 14: USART1 clock enable */
#define GPIOA ((volatile long *) 0x48000000)
#define GPIOB ((volatile long *) 0x48000400)
#define GPIO( x) CAT( GPIO, x)
#define MODER 0
#define ODR 5
#define AFRH 9
#define USART1 ((volatile long *) 0x40013800)
#define CR1 0 /* Config */
#define BRR 3 /* Baudrate */
#define ISR 7 /* Interrupt and Status */
#define TDR 10 /* Transmit Data */
#define USART_CR1_TE 8 /* 3: Transmit Enable */
#define USART_CR1_RE 4 /* 2: Receive Enable */
#define USART_CR1_UE 1 /* 0: USART Enable */
#define USART_ISR_TXE (1 << 7) /* 7: Transmit Data Register Empty */
/* user LED ON when PA4 is high */
#define LED_IOP A
#define LED_PIN 4
#define LED_ON 1
void kputc( unsigned char c) {
static unsigned char lastc ;
if( c == '\n' && lastc != '\r')
kputc( '\r') ;
/* Active wait while transmit register is full */
while( (USART1[ ISR] & USART_ISR_TXE) == 0) ;
USART1[ TDR] = c ;
lastc = c ;
}
int puts( const char *s) {
while( *s)
kputc( *s++) ;
kputc( '\n') ;
return 0 ;
}
volatile unsigned uptime ; /* seconds elapsed since boot */
#ifdef LED_ON
static void userLEDtoggle( void) {
GPIO( LED_IOP)[ ODR] ^= 1 << LED_PIN ; /* Toggle User LED */
}
#endif
void SysTick_Handler( void) {
uptime += 1 ;
#ifdef LED_ON
userLEDtoggle() ;
#endif
}
int init( void) {
/* By default SYSCLK == HSI [8MHZ] */
/* SYSTICK */
SYSTICK_RVR = 1000000 - 1 ; /* HBA / 8 */
SYSTICK_CVR = 0 ;
SYSTICK_CSR = 3 ; /* HBA / 8, Interrupt ON, Enable */
/* SysTick_Handler will execute every 1s from now on */
#ifdef LED_ON
/* User LED ON */
RCC_AHBENR |= RCC_AHBENR_IOP( LED_IOP) ; /* Enable IOPx periph */
GPIO( LED_IOP)[ MODER] |= 1 << (LED_PIN * 2) ; /* LED_IO Output [01],
** over default 00 */
/* OTYPER Push-Pull by default */
/* Pxn output default LOW at reset */
# if LED_ON
userLEDtoggle() ;
# endif
#endif
/* USART1 9600 8N1 */
RCC_AHBENR |= RCC_AHBENR_IOP( A) ; /* Enable GPIOA periph */
GPIOA[ MODER] |= 0x0A << (9 * 2) ; /* PA9-10 ALT 10, over default 00 */
GPIOA[ AFRH] |= 0x110 ; /* PA9-10 AF1 0001, over default 0000 */
RCC_APB2ENR |= RCC_APB2ENR_USART1EN ;
USART1[ BRR] = 8000000 / 9600 ; /* PCLK [8MHz] */
USART1[ CR1] |= USART_CR1_UE | USART_CR1_TE ; /* Enable USART & Tx */
return 0 ;
}
/* end of uplow.1.c */