Electronic – PIC16F877A: Transmitting data but not receiving from Bluetooth module

bluetoothpic

I interfaced PIC16F877A with a HC-05 Bluetooth module using serial communication and I can transmit data from the PIC to my PC. I connected my PC's Bluetooth to HC-05 Bluetooth module and in Tera Term or termite 2.9 I see the output. However, when I send data from the terminal I receive nothing on the PIC. As per my code the data received by PIC showed by echoed back by transmitting the same.

My PIC code

#include <htc.h>
__CONFIG(0x2F0A);
#define _XTAL_FREQ  16000000
#define BAUDRATE 9600
void InitUART(void)
{
    BRGH = 1;
    SPBRG = ((_XTAL_FREQ/16)/BAUDRATE) - 1;
    TRISC6 = 0; // TX Pin
    TRISC7 = 1; // RX Pin 
    TXSTA = 0x24;
    RCSTA = 0x90;
    //SPBRG  = 129;
}
void SendByteSerially(unsigned char Byte) // Writes a character to the serial port
{
    while(!TXIF) ; // wait for previous transmission to finish
    TXREG = Byte;
}

unsigned char ReceiveByteSerially(void) // Reads a character from the serial port
{
while(!RCIF)
    continue;   // Wait for transmission to receive
return RCREG;
}

void SendStringSerially(const unsigned char* st)
{
    while(*st)
        SendByteSerially(*st++);
}


void main (void)
{
    unsigned char SerialData;
    unsigned int i;
    TRISB=0x00;
    PORTB=0xff;
    InitUART(); // Intialize UART
    SendStringSerially("Hello World");
    while(1)
    {
    PORTB=0x00;
    for(i=0; i<100; i++)
        __delay_ms(10);
    PORTB=0x01;         
    for(i=0; i<100; i++)
        __delay_ms(10);
    SerialData = ReceiveByteSerially();
    SendByteSerially(SerialData);
    }
}

In the while loop I blink a LED for 1 second if any data is received.

Best Answer

The HC-05 Bluetooth module runs off a 3.3V supply. If you're running your PIC off 5V then you'll need to level-shift the module's 3.3V output signal to a 5V signal input to the PIC. Figure 6 in the product guide manual:

http://www.mcu-turkey.com/wp-content/uploads/2013/01/HC-Serial-Bluetooth-Products-201104.pdf

...shows how to do that with a couple of transistors.

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