Hello once again.... 
Finally i got a steady transmission signal with steady 125kHz. So i need the receiver to actually receive something.
But, surprise...new problems ...
What i was trying to do was get The timer2 to have interrupts every 8us (125kHz) and i managed to do it:
(RxPin is 4 and it's connected to a simple switch, pinT2 is 5 and i'm using Arduino UNO)
VLC.cpp
static char RxPin = 4;
static char pinT2 = 5;
static int rx_sample = 0;
static int rx_last_sample = 0;
static uint8_t rx_count = 0;
static uint8_t rx_sync_count = 0;
static uint8_t rx_mode = RX_MODE_IDLE;
static unsigned int rx_manBits = 0; //the received manchester 32 bits
static unsigned char rx_numMB = 0; //the number of received manchester bits
static unsigned char rx_curByte = 0;
static unsigned char rx_maxBytes = 2;
static unsigned char rx_default_data[2];
static unsigned char* rx_data = rx_default_data;
void MANRX_SetRxPin(char pin)
{
RxPin = pin;
if (pin <=7){
RxPin = pin; // user sets the digital pin as input
DDRD &= ~(1<<RxPin); //pinMode(RxPin, INPUT);
}
else if ((pin >= 8) || (pin <= 13)){
RxPin = pin - 8; // user sets the digital pin as input
DDRB &= ~(1<<RxPin); //pinMode(RxPin, INPUT);
}
}//end of set reception pin
void MANRX_SetupReceive()
{
DDRD &= ~(1<<RxPin); // default pinMode(RxPin, INPUT);
/*
Timer 2 is used with a ATMega328. The base clock is 16MHz.
- If we don't use any clock divider which gives 62.5 nS per count.
- If we use /8 as clock divider resulti is 0.5 usS per count.
PS = 1 (Prescaler)
1 / (16,000,000 / PS) = 62.5nS/count
PS = 8 (Prescaler)
1 / (16,000,000 / PS) = 0.5uS/count
NRZ frequency is half the Tx signal (Manchester Encoded)
So, F_NRZ = 125kHz => 8us/bit (time of each bit)
PS=1 => 8us/62.5ns = 128
PS=1 => 8us/0.5us = 16
*/
TCCR2A = _BV(WGM21); // reset counter on match
TCCR2B &= ~(_BV(CS10) | _BV(CS11) | _BV(CS12));// reset clock select register, and starts the clock
TCCR2B |= _BV(CS11);//counts every 0.5usec with 16 Mhz clock
OCR2A = 15; // interrupt every 16 counts (0->15)
TIMSK2 = _BV(OCIE2A); // Turn on interrupt
TCNT2 = 0; // Set counter to 0
}
void MANRX_BeginReceive(void)
{
rx_maxBytes = 2;
rx_data = rx_default_data;
rx_mode = RX_MODE_PRE;
}
void test_t2(char pin)
{
if (pin <=7){
pinT2 = pin; // user sets the digital pin as output
DDRD = DDRD | B0000001 | (1<<pinT2); //pinMode(TxPin, OUTPUT);
PORTD |= _BV(pinT2);
}
else if ((pin >= 8) || (pin <= 13)){
pinT2 = pin - 8; // user sets the digital pin as output
DDRB = DDRB | B0000001 | (1<<pinT2); //pinMode(TxPin, OUTPUT);
PORTB |= _BV(pinT2);
}
}
unsigned int MANRX_GetMessage(void)
{
return (((int)rx_data[0]) << 8) | (int)rx_data[1];
}
ISR(TIMER2_COMPA_vect)
{
PORTD |= (1<<pinT2);
unsigned char test = (PIND & (1<<RxPin));
rx_data[1] = test;
rx_data[0] = 0x00;
PORTD &= ~(1 << pinT2);
}
VLC.h - class Manchester refers to transmission and it's working
/*
This code is based on the Atmel Corporation Manchester
Coding Basics Application Note.
http://www.atmel.com/dyn/resources/prod_documents/doc9164.pdf
Quotes from the application note:
"Manchester coding states that there will always be a transition of the message signal
at the mid-point of the data bit frame.
What occurs at the bit edges depends on the state of the previous bit frame and
does not always produce a transition. A logical “1” is defined as a mid-point transition
from low to high and a “0” is a mid-point transition from high to low.
*/
#ifndef VLC_h
#define VLC_h
#define TxDefault 8 //the digital pin to use to transmit data
#define RxDefault 4 //the digital pin to use to receive data
#define RX_MODE_PRE 0
#define RX_MODE_SYNC 1
#define RX_MODE_DATA 2
#define RX_MODE_MSG 3
#define RX_MODE_IDLE 4
#define TimeOutDefault -1 //the timeout in msec default blocks
#if defined(ARDUINO) && ARDUINO >= 100
#include "Arduino.h"
#else
#include "WProgram.h"
#include <pins_arduino.h>
#endif
class MANCHESTERClass
{
public:
MANCHESTERClass(); //the constructor
void SetPW(unsigned int interval); // user sets the pulse width of half bit
void SetTxPin(char pin); //set the arduino digital pin for transmit. default 4.
void Transmit(unsigned int data); //transmit 16 bits of data
void TransmitBytes(unsigned char numBytes, unsigned char *data); // transmit a byte array
private:
unsigned char TxPin;
unsigned int HALF_BIT_INTERVAL;
};//end of class MANCHESTER
// Cant really do this as a real C++ class, since we need to have
// an ISR
extern "C"
{
//for debugging only - tests T2 interrupts
extern void test_t2(char pin);
//set the arduino digital pin for receive. default 4.
extern void MANRX_SetRxPin(char pin);
//begin the timer used to receive data
extern void MANRX_SetupReceive();
// begin receiving 16 bits
extern void MANRX_BeginReceive(void);
// fetch the received message
extern unsigned int MANRX_GetMessage();
}
extern MANCHESTERClass MANCHESTER;
#endif
MAIN PROGRAM
#include <VLC.h>
#include <avr/io.h>
#define RxPin 4
#define pinT2 5
void setup()
{
test_t2(pinT2); // tests T2 frequency interrupts
MANRX_SetRxPin(RxPin); // Set digital TX pin
MANRX_SetupReceive(); // Prepare interrupts
MANRX_BeginReceive(); // Begin receiving data
Serial.begin(115200); // Debugging only
}//end of setup
void loop()
{
unsigned int data = MANRX_GetMessage();
MANRX_BeginReceive();
//unsigned int data = 0x0010;
Serial.println(data);
}//end of loop
So there are a couple of things happenning that i really don't understand.
(1) When i erase this 1st line (while keeping the second) my interruptions appear every 250us instead of 8us. What am i missing here?
TCCR2B &= ~(_BV(CS10) | _BV(CS11) | _BV(CS12));// reset clock select register, and starts the clock
TCCR2B |= _BV(CS11);//counts every 0.5usec with 16 Mhz clock
(1.1) While the 1st line is deleted i can change switch on pin 4 and serial monitor updates accordingly and that is fine. But why doesn't update when that 1st line is present?
(2) Now i add this line to ISR:
ISR(TIMER2_COMPA_vect)
{
[b]TCNT2 = 0; // Set counter to 0[/b]
PORTD |= (1<<pinT2);
.......
}
why the serial monitor updates then stops nad only updates again when i reset?
(2.1) And why he updates a few times pin4 status when he is high and only half dozen when it's low? :S
(3)Wasn't supposed to interrupts have the same timming? Depending on the code i get less frequency....
For example...the code in ISR from VLC.cpp drops my freq to 120kHz and it even have 1/10 of what is needed.
Plz enlight me...
Thanks for support,
Fernando Oliveira
