#hc06

Second step

Write initalization function for USART1. The example of function is below.

/** * Function initialises USART1 with given baudrate. * @param baudrate given baudrate * */ void init_USART1(int baudrate) { /* GPIO structure for initialisation */ GPIO_InitTypeDef GPIO_InitStruct; /* USART structure for initalisation */ USART_InitTypeDef USART_InitStruct; /* NVIC structure for initalisation */ NVIC_InitTypeDef NVIC_InitStruct; /* For USART1 enable clock on APB2 bus*/ RCC_APB2PeriphClockCmd(RCC_APB2Periph_USART1, ENABLE); /* For GPIOB enable clock on AHB1 bus */ RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOB, ENABLE); /* Forming GPIO structure */ GPIO_InitStruct.GPIO_Pin = GPIO_Pin_6 | GPIO_Pin_7; //pin 6(TX), pin7(RX) GPIO_InitStruct.GPIO_Mode = GPIO_Mode_AF; GPIO_InitStruct.GPIO_Speed = GPIO_Speed_50MHz; GPIO_InitStruct.GPIO_OType = GPIO_OType_PP; GPIO_InitStruct.GPIO_PuPd = GPIO_PuPd_UP; /* Initalization of GPIO */ GPIO_Init(GPIOB, &GPIO_InitStruct); /* Give USART1 control over GPIOB pins 6 and 7*/ GPIO_PinAFConfig(GPIOB, GPIO_PinSource6, GPIO_AF_USART1); GPIO_PinAFConfig(GPIOB, GPIO_PinSource7, GPIO_AF_USART1); /* Forming USART initalisation structure */ USART_InitStruct.USART_BaudRate = baudrate; USART_InitStruct.USART_WordLength = USART_WordLength_8b; USART_InitStruct.USART_StopBits = USART_StopBits_1; USART_InitStruct.USART_Parity = USART_Parity_No; USART_InitStruct.USART_HardwareFlowControl = USART_HardwareFlowControl_None; USART_InitStruct.USART_Mode = USART_Mode_Tx | USART_Mode_Rx; /* Initialisation of USART1 */ USART_Init(USART1, &USART_InitStruct); /* Enabling interrupt for USART1 */ USART_ITConfig(USART1, USART_IT_RXNE, ENABLE); /* Forming NVIC structure */ NVIC_InitStruct.NVIC_IRQChannel = USART1_IRQn; NVIC_InitStruct.NVIC_IRQChannelPreemptionPriority = 0; NVIC_InitStruct.NVIC_IRQChannelSubPriority = 0; NVIC_InitStruct.NVIC_IRQChannelCmd = ENABLE; /* NVIC initialisation */ NVIC_Init(&NVIC_InitStruct); /* Enabling USART1 */ USART_Cmd(USART1, ENABLE); }

Third step

Write function that sends bytes to USART. This can be done like this:

void USART_puts(char* bytes) { while(*bytes) { //waits until USART1 is ready while(!(USART1->SR & 0x40)); USART_SendData(USART1, *bytes); bytes++; } }

Fourth step

Write interrupt handler function. It is defined that interrupt function for USART1 has prototype:

void USART1_IRQHandler(void);

This is example of interrupt function which will echo data received. This way in terminal you will see data you send to STM32F4.

void USART1_IRQHandler(void) { //checks if interrupt is set by USART1 if(USART_GetITStatus(USART1, USART_IT_RXNE)) { char byteReceived = USART1->DR; USART_puts(&byteReceived); } }

Fifth step

Writing main function shouldn't be problem because it only initialises USART and stays in infinite loop. Here is the code:

int main() { init_USART1(9600); while(1) { //waits forever } }

Bluetooth modules HC06 or HC05

After all this coding you may ask yourself: "OK, where in code I specify bluetooth module or something similiar?". Bluetooth is not mentioned because module and MCU communicate via USART interface. If you don't have bluetooth module or android phone you can test this code with Silabs CP2102 or similiar module for serial communication with USB interface. On other hand, if you want bluetooth communication with your android phone download android bluetooth terminal and connect HC06 bluetooth module to your STM32F4. Make sure that you connect HC06's RX to STM's TX and HC06's TX to STM's RX. HC06 can be powered with 3.3V - 5V. You can download HC05 & HC06 datasheets on this link. Below you can see the picture of HC06 with development board.