Unable to connect usart1 to bluetooth hc-05

Posted on June 16, 2018 at 16:35

I've been trying to connect USART_1 with bluetooth hc-05 for the past few days, andI am unable to do so. The Microcontroller I am using is nucleo STM32F103RB.

Here's the code (I am not using any library)

#define APB2_FREQ 72000000

void USART1_Send(char* data)

{

unsigned int length = 0;

while(data[length] != '\0')

++length;

int i = 0;

while(i < length)

{

USART1_DR = data[i];

while((USART1_SR & 0x00000080) == 0); // wait if transmit data register is not empty

++i;

}

}

char USART1_Receive()

{

while((USART1_SR & 0x00000020) == 0); //wait for data to arrive

return USART1_DR;

}

void USART1_Init(int baudrate, short parity, short stop)

{

RCC_APB2ENR |= 0x00004004; // enable Port A, enable usart1 clock

GPIOA_CRH &= 0xFFFFF00F;

GPIOA_CRH |= 0x000004A0; // pin 9 = alternate function push-pull, pin 10 = Floating Input

USART1_CR1 &= 0x00000000; // clear CR1 register and 'M bit' to 0(which is 8 bit data)

if(parity == 1) // even parity

USART1_CR1 |= 0x00000400;

else if(parity == 2)

USART1_CR1 |= 0x00000600; // odd parity

USART1_CR2 &= 0x00000000; // Reset USART_CR2, 1 stop bit

if(stop == 2)

USART1_CR2 |= 0x00002000; // 2 stop bit

USART1_BRR = APB2_FREQ /(baudrate);

USART1_CR1 |= 0x00002000; // enable UART

USART1_CR1 |= 0x0000000C; // enable Transmiter, receiver

USART1_Send('LINK OK:\r\n');

}

int main(void)

{

USART1_Init(9600, 0, 1); // 9600 baudrate, no parity, 1 stop bit

while(1){

USART1_Send('Hello World\n');

}

return (1);

}

This

program, configures USART1 and transmits Hello World. When I run the code in Keil uvision4, uart1 window prints Hello World repeatedly.

https://i.stack.imgur.com/oMl4o.png

However when I burn the code in STM32F103RB, and connect it with Bluetooth and pair the bluetooth with my mobile, it doesn't display anything on Bluetooth Terminal app in Mobile.

Here's how I've hooked up the wires,

• Bluetooth Ground > STM32 Ground
• Bluetooth 5v > STM32 5v
• Bluetooth Rx > STM32 PA9
• Bluetooth Tx > STM32 PA10

I've tried the same Bluetooth with arduino and it worked fine.

Thanks!!!

#uart #stm32f103rb #bluetooth #keil-uvision

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