I'm trying to work my way step by step through building a remote control for the tv in my dining room. This is the part I'm on now. I have a 328p that I put a bootloader on using this board file:
So, my first question is about these fuse settings. They seem to be working, but is there anything weird about them that could cause trouble?
Next topic... Here is my program's code so far (comments explain what I think it should be doing):
#include <avr/io.h>
int Timer2APin = 11; // OC2A PIN = PORT B PIN 3 = ATMEGA328 PIN 17 = ARDUINO PIN 11
void setup(){
pinMode(Timer2APin, INPUT); // SETS DATA DIRECTION REGISTER
// OUTPUT WILL NOT SHOW UP WHILE SET TO INPUT
// OUTPUT WILL SHOW UP WHILE SET TO OUTPUT
TCNT2 = 0; // RESET COUNTER2 VALUE
OCR2A = 104; // SET TOP COUNTER2 VALUE (FOR CTC)
// formula from datasheet for ctc
// f_clk_io
// f_OC2A = ---------------------------
// 2 * prescale * (1 + OCR2A)
// 8000000
// f_OC2A = ------------------- = 38095.2381 Hz
// 2 * 1 * (1 + 104)
// SET VALUE OF TCCR2A
// (0 << COM2A1) | (1 << COM2A0) TOGGLE OC2A PIN ON COMPARE MATCH
// (0 << COM2B1) | (0 << COM2B0) OC2B PIN DISCONNECTED
// (1 << WGM21) | (0 << WGM20) CTC MODE - WGM22 IN TCCR2B MUST ALSO BE 0
TCCR2A = ((0 << COM2A1) | (1 << COM2A0) | (0 << COM2B1) | (0 << COM2B0) | (1 << WGM21) | (0 << WGM20));
// SET VALUE OF TCCR2B
// (0 << FOC2A) | (0 << FOC2B) FORCE OUT COMPARE A AND B OFF
// (0 << WGM22) CTC MODE - WGM21 AND WGM20 IN TCCR2A MUST ALSO BE 1 AND 0 RESPECTIVELY
// (0 << CS22) | (0 << CS21) | (1 << CS20) CLOCK SELECT - NO PRESCALAR
TCCR2B = ((0 << FOC2A) | (0 << FOC2B) | (0 << WGM22) | (0 << CS22) | (0 << CS21) | (1 << CS20));
}
void loop(){
pinMode(Timer2APin, OUTPUT); //let the timer pin toggle for 5 seconds
delay(5000);
pinMode(Timer2APin, INPUT); //stop it for 5 seconds
delay(5000);
}
So, it would seem that one or more of the things above are not working as expected. Circuit picture is in attachment. This is the receiver I'm using:
I was expecting to see the led hooked up to the detector alternate between on and off for 5 seconds at a time. Instead it is almost always on dimly, and it sort of flickers every once in a while. I hooked up another arduino as a logic analyzer and got what looked like erratically spaced pulses of varying lengths. Any ideas what is wrong with my code?
Also, I know people have libraries to do this already, but I want to understand what I'm doing. I think I'll learn more and understand better by writing my own code and asking questions.
Have you tried a simple sketch that doesn't have all that timer manipulation in, that just toggles an output pin at regular intervals so you can confirm the program has loaded, booted and is running?
After putting the bootloader on it, I uploaded the blink example to make sure the clock was working right and it was running at the right speed. The blinking speed was right, and everything seemed ok. Is that what you meant?
I can't really see in the datasheet where it warns you about this, except for this sentence on page 155:
When writing to one of the registers TCNT2, OCR2x, or TCCR2x, the value is transferred to a temporary register, and latched after two positive edges on TOSC1. The user should not write a new value before the contents of the temporary register have been transferred to its destination.
This was under the heading "Asynchronous Operation of Timer/Counter2" which doesn't seem to apply. However you might say that until we have established a timer mode, perhaps changing OCR2x goes into the temporary register, and is not latched because the timer is not running. However that's just a guess.
So just to make sure I understand what I'm reading / doing here, the #define part is there for the compiler, right? An you would do that instead of making a variable because you don't actually need the arduino to know what the number is, so you save some space by having the compiler replace it before uploading?
