mirror of
https://github.com/rfivet/stm32bringup.git
synced 2024-11-15 17:15:57 -05:00
125 lines
3.6 KiB
C
125 lines
3.6 KiB
C
/* uplow.2.c -- uptime lower layer
|
|
** Copyright (c) 2020 Renaud Fivet
|
|
**
|
|
** implements system.h interface
|
|
** uptime = seconds elapsed since boot
|
|
** SysClck 8MHz HSI based, baudrate 9600, Busy wait transmission
|
|
** user LED toggled every second
|
|
** SysTick interrupt every second
|
|
*/
|
|
|
|
#include "system.h" /* implements system.h */
|
|
|
|
#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) { /* character output */
|
|
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 kputs( const char s[]) { /* string output */
|
|
int cnt = 0 ;
|
|
int c ;
|
|
|
|
while( (c = *s++) != 0) {
|
|
kputc( c) ;
|
|
cnt += 1 ;
|
|
}
|
|
|
|
return cnt ;
|
|
}
|
|
|
|
void yield( void) { /* give way */
|
|
__asm( "WFI") ; /* Wait for System Tick Interrupt */
|
|
}
|
|
|
|
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.2.c */
|