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/*
Program : cro.c
author : Ajith Kumar (ajith@iuac.res.in)
License : GNU GPL version 3 or above
On receiving a single byte command,reads ADC channel 0 500 times, with 100 usec timegap
and returns a 'D' followed by 500 bytes of data. No error checking implemented.
*/
#include <avr/io.h>
#define READBLOCK 1 // code for readblock is 1
#define NS 500 // Maximum 1800 for ATmega32, with 2K RAM
#define TG 100 // 100 usec between samples
uint8_t tmp8, dbuffer[NS];
uint16_t tmp16;
int main (void)
{
// Initialize the RS232 communication link to the PC 38400, 8, 1, N
UCSRB = (1 << RXEN) | (1 << TXEN);
UBRRH = 0;
UBRRL = 12; // At 8MHz clock (12 =>38400 baudrate)
UCSRC = (1 <<URSEL) | (1 << UCSZ1) | (1 << UCSZ0); // 8,1,N
ADCSRA = (1 << ADEN); // Enable the ADC
for(;;) // Infinite loop waiting for commands from PC
{
while ( !(UCSRA & (1<<RXC)) ); // wait for data from PC
if(UDR == 1) // '1' is our command
{
TCCR1B = (1 << CS11); // TC1 in Normal mode, 8 MHz/8, 1 usec per count
ADMUX = (1 << REFS0) |(1 << ADLAR) | 0; // 8 bit mode, AVCC ref, channel 0
ADCSRA |= ADIF; // reset ADC DONE flag
for(tmp16 = 0; tmp16 < NS; ++tmp16) // Digitize nsamples times
{
TCNT1 = 1;
ADCSRA |= (1 << ADSC) | 1; // Start AD conversion, ADC clock divider is 1
while ( !(ADCSRA & (1<<ADIF)) ) ; // wait for conversion to complete
dbuffer[tmp16] = ADCH; // Collect Data and store it
ADCSRA |= ADIF; // reset ADC DONE flag
while(TCNT1L < TG) ; // Wait on counter for the specified time gap
}
// Why we are NOT sending data inside the above loop. Think about it.
while( !(UCSRA & (1 <<UDRE) ) ); // Wait for transmit buffer empty flag
UDR = 'D'; // Send the response byte in all cases
for(tmp16=0; tmp16 < NS; ++tmp16) // Send the collected data to the PC
{
while( !(UCSRA & (1 <<UDRE) ) );
UDR = dbuffer[tmp16];
}
}
}
}
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