Timemachine

Introduction

So, here is the thing. I wanted to measure, how long will my batteries in accelerometer over Bluetooth last. I got an idea to write a simple program for my Atmega8. It was also a great way how to learn something new. And i did! :) Now i can r/w from/into internal EEPROM and i learned from michai that i can't read from ports using PORTx and that i need to use PINx.
Anyway, power source of accelerometer data over bluetooth uses LP2951CM IO, which has /ERROR output. It goes low, when output voltage drops 5% below configured voltage. It's an indication of low voltage on batteries ( aka. battery depleted ). And for the PRO folks, i know that precision of this setup isn't much, but it should do the trick.

This is how does the output from /dev/ttyUSBx looks like ( after testing, watching episode of Southpark ^_^ ) <enscript> 000:022:013: </enscript>

Timemachine setup

Source Code

<syntaxhighlight lang="c">

1. define F_CPU 4000000UL
2. define BAUD_RATE 19200

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

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) | (1<<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 receive (void) { //unsigned char check=0; //unsigned char data=0; while(! (UCSRA & ( 1 << RXC )) ); /* check |= UCSRA; check &= 0b00011100; if(!check) return 1; // zavolat nejaku fce ktora "oznami" koniec/chybu

• /

return UDR; }

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 data ) { unsigned char pom_hodnota; unsigned int delitel = 100; while(delitel>=1)

       {
       pom_hodnota=data/delitel;
       data -= delitel*pom_hodnota;
       pom_hodnota += 48;
       delitel /= 10;
       transmit(pom_hodnota);
       }

}

void eeprom_write(unsigned int uiAddress, unsigned char ucData) { while(EECR & (1<<EEWE)); EEAR = uiAddress; EEDR = ucData; EECR = (1<<EEMWE); EECR = (1<<EEWE); // EECR |= (1<<EEMWE); // EECR |= (1<<EEWE); }

unsigned char eeprom_read(unsigned int uiAddress) { while(EECR & (1<<EEWE)); EEAR = uiAddress; EECR |= (1<<EERE); return EEDR; }

int main(void) { unsigned char i,data,hh=0,mm=0,ss=0; unsigned int address,value; DDRB = 0x00; init_uart(); data = PINB; data &= 0b10000000; while(data) { ++ss; if(ss == 60 ) { ++mm; ss -= 60; } else if( mm == 60 ) { ++hh; mm -= 60; } data = PINB; data &= 0b10000000; _delay_ms(1000); } eeprom_write(0,hh); _delay_ms(100); eeprom_write(1,mm); _delay_ms(100); eeprom_write(2,ss); for(i=0,address=0; i<3; i++,address++ ) { data=eeprom_read(address); decompose(data); transmit(':'); _delay_ms(100); } transmit('\n'); return 0; } </syntaxhighlight>

See Also

Btm-112
Accelerometer data over bluetooth