Sample

[Xodor]

Hi Erik,

is it possible to provide a small sample, where this lib is included ?

Klaus

[eriksl]

is it possible to provide a small sample, where this lib is included ?

Have a look here: http://github.com/eriksl/attiny861_1

What are you making?

[Xodor]

Hi Erik,

 

i want to control a led, and learn about avr programming.

the address of my slave should be 0x55 and the commands are:

0x01 : led on

0x02 : led off

 

But nothing is working.

 

In the link at bottom, you can find my testproject

 

If you can help me get this working, i would be very glad.

 

Joern.

 

https://anonfiles.com/file/922e51f666e2e01cf6dd1bed79b44080

[Xodor]

Hi Erik,

i post it here.

#include <avr/interrupt.h>
#include <avr/io.h>
#include "usitwislave/usitwislave.h"

#define LED_OFF PORTB &= ~(1<<PB3)
#define LED_ON PORTB |= 1<<PB3

static void build_reply(uint8_t volatile *output_buffer_length, volatile uint8_t *output_buffer,
        uint8_t reply_length, const uint8_t *reply_string)
{
    uint8_t ix;

    output_buffer[0] = reply_length;

    for(ix = 0; ix < reply_length; ix++)
    {
        output_buffer[1 + ix] = reply_string[ix];
   }

    *output_buffer_length = reply_length + 1;
}

static void twi_callback(uint8_t buffer_size, volatile uint8_t input_buffer_length, const volatile uint8_t *input_buffer,
                        uint8_t volatile *output_buffer_length, volatile uint8_t *output_buffer)
{

    if (input_buffer_length > 0)
    {
        if (input_buffer[0] == 0x01)
        {
            LED_ON;
        }

        if (input_buffer[0] == 0x02)
        {
            LED_OFF;
        }

    }

    return(build_reply(output_buffer_length, output_buffer, 0, 0));
}

int main(void)
{
    DDRB |= 1<<PB3;

    usi_twi_slave(0x55, 0, twi_callback, 0);

    return 0;
}

[eriksl]

the address of my slave should be 0x55 and the commands are:
0x01 : led on
0x02 : led off
But nothing is working.

The first thing that comes to my mind is wrong i2c address. The adress
you supply to the library is the "plain" address. I2c shifts this
address by one bit for the read/write bit. So often you must use the
adress << 1. Or exactly the other way around address >> 1.

Otherwise are you sure that the electrical part is correct, pull up
resistors? You can hook up a transistor + led to the scl and sda lines
to see what happens (I did...). These lines are normally high, so you
should use an inverting circuit (led parallel over collector and
emitter, of course a resistor between + and the collector/led.

I've found out the internal pull up resistors of the attiny861 are not
always working. What microcontroller are you using? If you're using a
attiny861, you should also configure what pins are used for i2c.

Are you sure you program is even run? How about a second led that
flashes when the program runs (add this code and add a led):

#include <avr/delay.h>

DDRB = _BV(3) | _BV(4);

main()
{
PINB = _BV(4); // this toggles the led
_delays_ms(100);
}