Accelerometer data over bluetooth

Introduction

The story begins in one nice suuny morning when i came across project where the guy took a glove from some old nintendo console and remade it with accelerometer and bluetooth module. I watched his youtube movie without even breathing. A few months later came the time when it was necessary to pick up a bachelors project so i can get a degree. Searching for a right topic for me i came along "Data transmission over bluetooth" topic and i said myself, "this would be great to use bachelors project to make something i want". And that's, how it began :)

Accelerometer module

Image of accelerometer module
Where to buy?

Bluetooth module

Image
Module image

Eagle library
Eagle library.
Datasheet
Datasheet.
PCB
I used only one foil with 1200dpi printed movite. I have HP LaserJet P1005 printer.

Schematic

As you can see, i chosed the Atmega8 microprocessor. The reason was that i was playing a little bit with it before starting bachelors project, so i used my little base knowledge i already gained ;) What the Atmega does is that it reads and converts axes from accelerometer and send then over UART into bluetooth module.

Parts

Accelerometer Motorola/Freescale MMA7260Q
Microprocessor Atmel Atmega8
BT module Rayson BTM-112

Movie

<youtube width="330" height="220" align="left">YZGwKe6Cvhw</youtube>

May the source be with you

<enscript lang=c>

1. define F_CPU 8000000UL
2. define BAUD_RATE 19200

1. include <util/delay.h>
2. include <avr/io.h>

void init_adc(void) { ADCSRA = (1<<ADEN) | (0<<ADFR) | (0<<ADIE) | (1<<ADPS2) | (0<<ADPS1) | (0<<ADPS0);

       ADMUX = (0<<REFS1) | (1<<REFS0) | (1<<ADLAR) | (0<<MUX3) | (0<<MUX2) | (0<<MUX1) | (0<<MUX0);

}

void init_uart(void) { UCSRA = (0<<RXC) | (0<<TXC) | (0<<UDRE) | (0<<FE) | (0<<DOR) | (0<<PE) | (0<<U2X) | (0<<MPCM); UCSRB = (0<<RXCIE) | (0<<TXCIE) | (0<<UDRIE) | (0<<RXEN) | (1<<TXEN) | (0<<UCSZ2) | (0<<RXB8) | (0<<TXB8); UCSRC = (1<<URSEL) | (0<<UMSEL) | (0<<UPM1) | (0<<UPM0) | (0<<USBS) | (1<<UCSZ1) | (1<<UCSZ0) | (0<<UCPOL); //UBRRH = 0b00000000; //UBRRL = 0x02; UBRRH = (((F_CPU/BAUD_RATE)/16)-1)>>8; // set baud rate UBRRL = (((F_CPU/BAUD_RATE)/16)-1); }

unsigned char get_adc(unsigned char adc) { unsigned char value=0;

ADMUX = adc; ADCSRA |= (1<<ADSC);

while(!(ADCSRA & (1<<ADIF))) ;

value = ADCH;

ADCSRA &= ~(1<<ADIF);

return value; }

void transmit( unsigned char data ) {

while( !(UCSRA & ( 1 << UDRE ) ) )

     ;

UDR = data;

while (!(UCSRA & (1 << TXC ) ) ) // TXC == 0;

       ;

if((UCSRA & (1<<TXC))) // TXC != 0; UCSRA = (1 << TXC);

}

void decompose( unsigned char i ) { unsigned char j; unsigned int k = 1000;

while(i>0) { j=i/k; i -= k*j; j += 48; k /= 10; transmit(j); } }

int main(void) {

unsigned char i; unsigned char adc=0x20; unsigned int value=0,data[10];

init_adc(); init_uart();

while(1) {

for(i=0;i<10;i++) { data[i] = get_adc(adc); }

value = 0; for(i=0;i<10;i++) value += (unsigned int) data[i]; value /= 10;

switch(adc) { case 0x20: transmit('x'); transmit(':'); decompose(value); transmit(' '); break; case 0x21: transmit('y'); transmit(':'); decompose(value); transmit(' '); break; case 0x22: transmit('z'); transmit(':'); decompose(value); transmit('\n'); break;

default: transmit('0'); break; } ++adc; if(adc == 0x23) adc=0x20;

_delay_ms(30); } return 0; }

</enscript>

See Also

Btm-112