from: https://eroro.tistory.com/488
https://github.com/blalor/avr-softuart
위 사이트에 나와있는 소스코드를 STM32F103에서 동작하도록 변경
9600bps에 맞췄습니다만 본인이 사용하는 클럭 설정이나 다른 코어라면 코어의 처리 속도등을 고려해서 Timer의 발생 시간을 조절해주어야 합니다.
계산해보면 1/9600 = 0.00010416… 이므로 오차율 감안하고 104us정도 나오도록 오실로스코프로 계산하면서 맞춰주면 될 것 같습니다.
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#include <stdarg.h> #include <stdio.h> #define SU_TRUE 1 #define SU_FALSE 0 // 1 Startbit, 8 Databits, 1 Stopbit = 10 Bits/Frame #define TX_NUM_OF_BITS (10) volatile static unsigned char flag_tx_busy; volatile static unsigned char timer_tx_ctr; volatile static unsigned char bits_left_in_tx; /* ! mt: was type uchar - this was wrong */ volatile static unsigned short internal_tx_buffer; #define UARTTXPORT GPIOA #define UARTTXPIN GPIO_Pin_9 #define set_tx_pin_high() GPIO_SetBits(UARTTXPORT, UARTTXPIN) #define set_tx_pin_low() GPIO_ResetBits(UARTTXPORT, UARTTXPIN) extern void TIM2_IRQHandler(void); void TIM2_IRQHandler(void) { if (TIM_GetITStatus(TIM2, TIM_IT_Update) != RESET) { TIM_ClearITPendingBit(TIM2, TIM_IT_Update); Tim2_IRQ(); } } void Tim2_IRQ(void) { unsigned char tmp; // Transmitter Section if ( flag_tx_busy == SU_TRUE ) { tmp = timer_tx_ctr; if ( --tmp == 0 ) { // if ( --timer_tx_ctr <= 0 ) if ( internal_tx_buffer & 0x01 ) { set_tx_pin_high(); } else { set_tx_pin_low(); } internal_tx_buffer >>= 1; tmp = 3; // timer_tx_ctr = 3; if ( --bits_left_in_tx == 0 ) { flag_tx_busy = SU_FALSE; } } timer_tx_ctr = tmp; } } void gpio_init(void) { GPIO_InitTypeDef GPIO_InitStruct; /* Enable the GPIO_LED clock */ RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA, ENABLE); /* mt: set to high to avoid garbage on init */ set_tx_pin_high(); /* Configure Led pin as output */ GPIO_InitStruct.GPIO_Pin = UARTTXPIN; GPIO_InitStruct.GPIO_Mode = GPIO_Mode_Out_PP; GPIO_InitStruct.GPIO_Speed = GPIO_Speed_50MHz; GPIO_Init(UARTTXPORT, &GPIO_InitStruct); flag_tx_busy = SU_FALSE; } void timer_init(void) { TIM_TimeBaseInitTypeDef TIM_TimeBaseStructure; NVIC_InitTypeDef NVIC_InitStructure; RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM2, ENABLE); /* Time base configuration */ TIM_TimeBaseStructure.TIM_Period = 70 - 1; // Timer/Count2 Clock = 36Mhz / (35 + 1) = 1Mhz = 1 usec TIM_TimeBaseStructure.TIM_Prescaler = 35; TIM_TimeBaseStructure.TIM_ClockDivision = 0; TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up; // Ä«¿îÅ͸ðµåµ¿ÀÛ TIM_TimeBaseInit(TIM2, &TIM_TimeBaseStructure); /* TIM2 counter enable */ TIM_Cmd(TIM2, ENABLE); /* TIM IT enable */ TIM_ITConfig(TIM2, TIM_IT_Update, ENABLE); /* Enable the TIM2 gloabal Interrupt */ NVIC_InitStructure.NVIC_IRQChannel = TIM2_IRQn; NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0; NVIC_InitStructure.NVIC_IRQChannelSubPriority = 1; NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE; NVIC_Init(&NVIC_InitStructure); } void softuart_init( void ) { gpio_init(); /* 9600bps Setting */ timer_init(); } unsigned char softuart_transmit_busy( void ) { return ( flag_tx_busy == SU_TRUE ) ? 1 : 0; } void softuart_putchar( const char ch ) { while ( flag_tx_busy == SU_TRUE ) { ; // wait for transmitter ready // add watchdog-reset here if needed; } // invoke_UART_transmit timer_tx_ctr = 3; bits_left_in_tx = TX_NUM_OF_BITS; internal_tx_buffer = ( ch << 1 ) | 0x200; flag_tx_busy = SU_TRUE; } void softuart_puts( const char *s ) { while ( *s ) { softuart_putchar( *s++ ); } } void softuart_puts_P(char *string) { while(*string != '\0') softuart_putchar(*(string++)); } void softuart_print(const char *fmt,...) { char string[256]; va_list ap; va_start(ap,fmt); vsprintf(string,fmt,ap); va_end(ap); softuart_puts_P(string); } void main(void) { softuart_init(); softuart_print("\r\nSoftuart Demo-Application Start \r\n"); } |