Troubles about trying to send symbol from MCU to computer
  • Sanyee
    junior Member
    Posts: 1
    Joined: Sat Mar 31, 2018 5:12 am

    Troubles about trying to send symbol from MCU to computer

    by Sanyee » Fri Apr 06, 2018 8:34 am

    Having programmed 8-bit AVR MCU's, I bought Blue Pill STM32F103C8 dev board from ebay. It has 8MHz external crystal and I program it with ST-Link on Mac. I saw a lot of options like HAL, etc, but I chose to program using direct access to registers and with core of CMSIS.

    My problem is that I am trying to send symbol from MCU to computer. I am using CP2102( module connected to USART1(PB6 and PB7). LEDs are blinking, but I don't get any output in Arduino IDE serial monitor. Here is my code:

    Code: Select all

    #include "stm32f1xx.h" void delay(unsigned long delay) { while(delay) delay--; } int SendChar (int ch) { while (!(USART1->SR & USART_SR_TXE)); USART1->DR = (ch & 0xFF); return (ch); } int main(void) { //Enable I2C2 clock RCC->APB1ENR |= RCC_APB1ENR_I2C2EN; //Enable the clock to PORT B, PORT C, USART1 and AFIO clocks RCC->APB2ENR |= RCC_APB2ENR_IOPBEN | RCC_APB2ENR_IOPCEN | RCC_APB2ENR_AFIOEN; RCC->APB2ENR |= RCC_APB2ENR_USART1EN; //use AFIO_MAPR register to remap alternate functions to use USART 1 TX and RX on PB6 and PB7 //Ref 7.4.2 and 6.3.7 in st manual AFIO->MAPR |= AFIO_MAPR_USART1_REMAP; //CRL Configures outputs 0 to 7 and CRH 8 to 15, so if you want to configure PC13, //you modify GPIOC_CRH register GPIOB->CRL |= GPIO_CRL_MODE0_0 | GPIO_CRL_MODE0_1; GPIOC->CRH = GPIO_CRH_MODE13_0 | GPIO_CRH_MODE13_1 | GPIO_CRH_MODE14_0 | GPIO_CRH_MODE14_1 | GPIO_CRH_MODE15_0 | GPIO_CRH_MODE15_1; //Set RX as floating in and TX as out push-pull GPIOB->CRL &= ~(GPIO_CRL_MODE7_0 | GPIO_CRL_MODE7_1); GPIOB->CRL |= GPIO_CRL_MODE7_0 | GPIO_CRL_MODE7_1 | GPIO_CRL_CNF6_0; //Enable RX TX USART1->CR1 |= (USART_CR1_RE | USART_CR1_TE); // RX, TX enable //Enable USART USART1->CR1 |= USART_CR1_UE; //Make sure to clear OVER8 bit(15 bit in USART_CR1) to oversample by 16, I dont know if I need this USART1->CR1 &= ~(1 << 15); ////Configure Baud Rate /*USART_BRR = Fck/BAUDRATE*/ //Set 115200 Baud, 8 MHz crystal USART1->BRR = 8000000L/115200L; while (1) { SendChar(35); //Test UART,fingers crossed //Toggle led on PB0 GPIOB->ODR ^= GPIO_ODR_ODR0; //Toogle RGB led connected on PC13, PC14 and PC5 GPIOC->ODR ^= GPIO_ODR_ODR13; delay(50000); GPIOC->ODR ^= GPIO_ODR_ODR13; delay(50000); GPIOC->ODR ^= GPIO_ODR_ODR15; delay(50000); } return 0; }

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