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Author Topic: I2C on the ATtiny85  (Read 21863 times)
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Denver
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Is there any fundamental reason why this would not work on attiny85?
I don't think there is. It was just a bit over my head so I didn't take the time to do it.

If you add those, let me know and I'll update the libs I put on the Playground.
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Posting in this old thread because this is the google top entry for attiny85 i2c and the question is relevant.

Does anyone know how to change the slave address for an Attiny?

The default appears to be 0x26 from the TinyWireS library code but i've been looking in the attiny85 datasheet and cannot find where it's specified nor how to change it (because I don't know what to look for).

I want to change it to allow me to connect to two (or more) Attiny85's.

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Denver
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You set the slave address in your sketch with the .begin -

#define I2C_SLAVE_ADDR  0x26            // i2c slave address (38)
TinyWireS.begin(I2C_SLAVE_ADDR);      // init I2C Slave mode
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Thanks.

I was actually most of the way through determining it for myself smiley

For anyone interested in I2C for the attiny and other atmel AVR mc's the atmel here's what I've found.

The atmel application notes can be found here http://www.atmel.com/products/microcontrollers/avr/tinyAVR.aspx?tab=documents

Scroll down and look for Application notes AVR310, AVR311, AVR312 and AVR315 and have a read. It's in here that I found the specification for the pullups, the C commands and process flow diagrams.

My determination is that to connect to multiple attiny85 slaves you skip the define and specify the address you want in the TinyWireS object begin method calls for each attiny you want to slave (or use multiple defines).

From what I could determine there is no default address, it's all in the initialisation (the begin function)
« Last Edit: February 22, 2012, 12:18:14 am by m12lrpv » Logged

Denver
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My determination is that to connect to multiple attiny85 slaves you skip the define and specify the address you want in the TinyWireS object begin method calls for each attiny you want to slave (or use multiple defines).

From what I could determine there is no default address, it's all in the initialisation (the begin function)

Ah yea. It  looks like what you determined pretty much agrees with my post above. That's nice.
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Hello,

Do you know if the TinyWire library also supports the ATtiny84? Thank you very much.

Pedro Santos
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i want to use the DS1307 with the attiny85 but i cant understand the example you provided. can you tell me how i can get the seconds, minutes and hours in to individual integers.
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Do you know if the TinyWire library also supports the ATtiny84? Thank you very much.

Yes, I have had success running on an ATtiny84.
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i want to use the DS1307 with the attiny85 but i cant understand the example you provided. can you tell me how i can get the seconds, minutes and hours in to individual integers.

Attached is the code I use to connect the DS1307 and a dfrobot I2C LCD to the attiny85 at 8mhz internal.

10k pullups on the SDA and SCL lines.

The base DS1307 code I got from tronixstuff. My liquidcrystal I2C library is modified to handle the DFrobot display. Other displays can have significant variations in function so the display part won't work for you straight up.

* clock_i2c_lcd.zip (2.22 KB - downloaded 52 times.)
« Last Edit: May 02, 2012, 06:43:48 am by m12lrpv » Logged

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hey when verifying the example code i get this error "C:\Users\Owner\Documents\Arduino\libraries\TinyWireM\USI_TWI_Master.cpp:329: error: 'USIPF' was not declared in this scope"

how do i fix this
and what do i need to change to run it at 8MHz
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There's a good chance you have arduino version issues and attiny core issues.

The reference you're missing is in the following file in my arduino environment.
\hardware\tools\avr\avr\include\avr\iotnx5.h

I'm using the http://code.google.com/p/arduino-tiny/ core exclusively now after encountering far too many issues burning fuses and general compiling with the high-low tech core.

I also followed coding badly's instructions for updating the AVR core and editing some of the files to get my environment correct first. Subsequently I have a hybrid 0022/1.0 arduino environment.

Unfortunately getting the environment correct is the first step. Setting yourself up to burn the fuses to 8mhz is a good first goal. If you can successfully do that you're environment should be right from then on.

Search the forum for attiny85 and 8mhz and you'll get there.
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thanks for the help i will get on to it now.
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I'm using a ATtiny85 using a Arduino Duemilanove as an ISP. The cores i'm using are located here: http://code.google.com/p/arduino-tiny/downloads/detail?name=arduino-tiny-0100-0012.zip ... i believe it's being referred to as the "google" cores.

I'm trying to communicate with 4 blinkm's over i2c using a ATtiny85 and the TinyWireM lib. I've already been able to do this using my Arduino to communicate over i2c with these blinkm's with the builtin Wire lib and everything works ... so I know that the blinkm's are functioning properly.

My code is here: https://gist.github.com/dae96d4658745cd966ec  ... It seems that the "change color" command is making it to the blinkm's but not the "stop script" command.

If anyone can help me out that'd be greatly appreciated.
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Do you have pull ups on the I2C lines?
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yes I have a 4.7K on pins 5 and 7. i've also re-fused the attiny85 back to 1mhz instead of 8mhz.
« Last Edit: July 07, 2012, 01:52:29 am by heatxsink » Logged

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