Not sure why my code keeps resetting but it starts working when I comment out this line of code "TIMSK5 |= 0b00000100; "
I am trying to integrate some timer driven RF transmit functionality developed by Anthony Stirk into my main project but it's causing my mega to run through the following subroutine and hang when it hits the next "delay(50);" statement. This subroutine is the first thing called in my setup().
void initialise_interrupt()
{
// Start Timer5
//cli(); // disable global interrupts
TCCR5A = 0; // set entire TCCR1A register to 0
TCCR5B = 0; // same for TCCR1B
OCR5A = F_CPU / 1024 / RTTY_BAUD - 1; // set compare match register to desired timer count:
TCCR5B |= (1 << WGM12); // turn on CTC mode:
// Set CS10 and CS12 bits for:
TCCR5B |= (1 << CS10);
TCCR5B |= (1 << CS12);
// enable timer compare interrupt:
[b]// TIMSK5 |= 0b00000100; // <-- COMMENTED CODE TO STOP RESET
[/b] //sei();
}
Basically what I am trying to do is setup a timer based interrupt on my mega, of which it has 6.
I've tried enabling different match interrupts, every timer I have and have been digging through the datasheet to no avail.
I've also tried commenting out other lines in the subroutine but the critical line of code is the "TIMSK5 |= 0b00000100; " line which activates my timer interrupt.
As far as I know no other libraries I have use timers at all so I have no idea what I've done wrong.
The test script which runs and works with timers is below:
/*
Interrupt Driven RTTY TX Demo
Transmits data via RTTY with an interupt driven subroutine.
By Anthony Stirk M0UPU
October 2012 Version 5
Thanks and credits :
Evolved from Rob Harrison's RTTY Code.
Compare match register calculation by Phil Heron.
Thanks to : http://www.engblaze.com/microcontroller-tutorial-avr-and-arduino-timer-interrupts/
RFM22B Code from James Coxon http://ukhas.org.uk/guides:rfm22b
Suggestion to use Frequency Shift Registers by Dave Akerman (Daveake)/Richard Cresswell (Navrac)
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
See <http://www.gnu.org/licenses/>.
*/
#include <avr/io.h>
#include <avr/interrupt.h>
#include <util/crc16.h>
#define ASCII 7 // ASCII 7 or 8
#define STOPBITS 2 // Either 1 or 2
#define TXDELAY 0 // Delay between sentence TX's
#define RTTY_BAUD 300 // Baud rate for use with RFM22B Max = 600
#define RADIOPIN 13
char datastring[80];
char txstring[80];
volatile int txstatus=1;
volatile int txstringlength=0;
volatile char txc;
volatile int txi;
volatile int txj;
unsigned int count=0;
//rfm22 radio1(RFM22B_PIN);
void setup()
{
Serial.begin(115200);
Serial.println("Start");
initialise_interrupt();
setupRadio();
}
void loop()
{
sprintf(datastring,"$$$M0UPU,%04u,RTTY TEST BEACON RTTY TEST BEACON",count); // Puts the text in the datastring
unsigned int CHECKSUM = gps_CRC16_checksum(datastring); // Calculates the checksum for this datastring
char checksum_str[6];
sprintf(checksum_str, "*%04X\n", CHECKSUM);
strcat(datastring,checksum_str);
delay(1000);
count++;
}
void initialise_interrupt()
{
Serial.println(TIMSK5);
// initialize Timer1
cli(); // disable global interrupts
TCCR5A = 0; // set entire TCCR1A register to 0
TCCR5B = 0; // same for TCCR1B
OCR5A = F_CPU / 1024 / RTTY_BAUD - 1; // set compare match register to desired timer count:
TCCR5B |= (1 << WGM12); // turn on CTC mode:
// Set CS10 and CS12 bits for:
TCCR5B |= (1 << CS10);
TCCR5B |= (1 << CS12);
// enable timer compare interrupt:
TIMSK5 =2;
sei(); // enable global interrupts
Serial.println((1 << OCIE1A));
Serial.println(TIMSK5);
}
ISR(TIMER5_COMPA_vect)
{
switch(txstatus) {
case 0: // This is the optional delay between transmissions.
txj++;
if(txj>(TXDELAY*RTTY_BAUD)) {
txj=0;
txstatus=1;
}
break;
case 1: // Initialise transmission, take a copy of the string so it doesn't change mid transmission.
strcpy(txstring,datastring);
txstringlength=strlen(txstring);
txstatus=2;
txj=0;
break;
case 2: // Grab a char and lets go transmit it.
if ( txj < txstringlength)
{
txc = txstring[txj];
txj++;
txstatus=3;
rtty_txbit (0); // Start Bit;
txi=0;
}
else
{
txstatus=0; // Should be finished
txj=0;
}
break;
case 3:
if(txi<ASCII)
{
txi++;
if (txc & 1) rtty_txbit(1);
else rtty_txbit(0);
txc = txc >> 1;
break;
}
else
{
rtty_txbit (1); // Stop Bit
txstatus=4;
txi=0;
break;
}
case 4:
if(STOPBITS==2)
{
rtty_txbit (1); // Stop Bit
txstatus=2;
break;
}
else
{
txstatus=2;
break;
}
}
}
void rtty_txbit (int bit)
{
if (bit)
{
digitalWrite(RADIOPIN,HIGH); // High
}
else
{
digitalWrite(RADIOPIN,LOW); // Low
}
}
void setupRadio(){
//pinMode(RFM22B_SDN, OUTPUT); // RFM22B SDN is on ARDUINO A3
pinMode(RADIOPIN,OUTPUT);
digitalWrite(RADIOPIN, LOW);
delay(1000);
/* rfm22::initSPI();
radio1.init();
radio1.write(0x71, 0x00); // unmodulated carrier
//This sets up the GPIOs to automatically switch the antenna depending on Tx or Rx state, only needs to be done at start up
radio1.write(0x0b,0x12);
radio1.write(0x0c,0x15);
radio1.setFrequency(RADIO_FREQUENCY);
radio1.write(0x6D, 0x04);// turn tx low power 11db
radio1.write(0x07, 0x08);
*/// delay(500);
}
uint16_t gps_CRC16_checksum (char *string)
{
size_t i;
uint16_t crc;
uint8_t c;
crc = 0xFFFF;
// Calculate checksum ignoring the first two $s
for (i = 5; i < strlen(string); i++)
{
c = string[i];
crc = _crc_xmodem_update (crc, c);
}
return crc;
}
*Modified adding code tags.
