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Topic: attiny85 VirtualWire to Mega2560 (Read 1 time) previous topic - next topic

Torkel

Hi!

I'm having some trouble with RF-communication (433MHz) between a attiny85 with 16MHz external oscillator and a Arduino Mega2560.

Receiver (Mega2560)
Code: [Select]

#include <VirtualWire.h>

void setup()
{
  // Initialise the IO and ISR
  Serial.begin(115200);
  Serial.println("Setup...");
  pinMode(13, OUTPUT);
  digitalWrite(13, LOW);
  vw_set_ptt_inverted(true);
  vw_setup(2000); // Bits per sec
  vw_rx_start();       // Start the receiver PLL running
}

void loop()
{
  uint8_t buf[VW_MAX_MESSAGE_LEN];
  uint8_t buflen = VW_MAX_MESSAGE_LEN;

  if (vw_get_message(buf, &buflen)) // Non-blocking
  {
    int i;

    digitalWrite(13, HIGH); // Flash a light to show received good message
    // Message with a good checksum received, dump it.
    Serial.print("Got: ");

    for (i = 0; i < buflen; i++)
    {
      Serial.print(buf[i]);
    }
    Serial.println("");
    digitalWrite(13, LOW);
  }
}


Transmitter
Code: [Select]

//Transmitter. Sends integer as 2 bytes once per second

#include <VirtualWire.h>
#undef round

uint16_t data =0;  //the integer to send

void setup()
{   
    vw_set_tx_pin(4);
    vw_setup(); // 2000 Bits per sec
}

void loop()
{
    data +=1;
    uint8_t number[2] ;
    number[0] = data;
    number[1] = data >> 8;  //send 2 bytes
    vw_send(number, 2);
    vw_wait_tx(); // Wait until the whole message is gone
    delay(1000);  //send every second
}


This code works fine when I use another Mega2560 for transmitting, but not with the attiny85. I assume this is some kind of timing error. That's why I use a 16MHz oscillator to the attiny, to match the Mega2560 in speed.

Since I don't yet own an oscilloscope, I connected LED's to the transmitting pin of both the attiny and the Mega2560 and I got some interesting results. It seems like the attiny takes almost a second to transfer the message when the Mega2560 does it in a couple of milliseconds (if even that long).

I had to change two rows in the VirtualWire-library to get it to compile on the attiny
Code: [Select]

#ifndef TEST
    // Set up timer1 for a tick every 62.50 microseconds
    // for 2000 bits per sec
    TCCR0A = 0; [b]<--- Changed TCCR1A to TCCR0A[/b]
    TCCR0B = _BV(WGM02) | _BV(CS10); [b]<--- Changed TCCR1B to TCCR0B and WGM12 to WGM02[/b]
    // Caution: special procedures for setting 16 bit regs
    OCR1A = ocr1a;
    // Enable interrupt
#ifdef TIMSK1
    // atmega168
    TIMSK1 |= _BV(OCIE1A);
#else
    // others
    TIMSK |= _BV(OCIE1A);
#endif

#endif


My boards.txt
Code: [Select]

attiny85at16.bootloader.low_fuses=0xFF
attiny85at16.bootloader.high_fuses=0xD7
attiny85at16.bootloader.extended_fuses=0xFF
attiny85at16.bootloader.path=empty
attiny85at16.bootloader.file=empty85at8.hex

attiny85at16.bootloader.unlock_bits=0xFF
attiny85at16.bootloader.lock_bits=0xFF

attiny85at16.build.mcu=attiny85
attiny85at16.build.f_cpu=16000000L
attiny85at16.build.core=tiny


What can I do to resolve this? I also tried to get two attiny85 to communicate with each other (both at 16MHz) and it worked fine (but slower than the Mega2560).

DevonMiles

Hi Torkel, sorry for my bad english. Unfortunately I can' t help you with your trouble, but I have a question for you and you could help me. I' m trying RF-communication between 2 attiny85 with external 16MHZ oscillator using your library modifications. I don' t understand why do you use vw_set_tx_pin(4). In this way I suppose you set pin PB4 (phisically pin n°3) like output for tx. Isn' t this pin used for the oscillator?
Thank you.
Regards.

Coding Badly


Does this help...
http://arduino.cc/forum/index.php/topic,63755.0.html

Or this...
http://arduino.cc/forum/index.php/topic,60239.0.html

DevonMiles


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