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So I am trying to understand bit banging and port operations. I'm developing a breakout board with an ADXL343 IMU read by an AtTiny44 via i2c. I adapted this code from MIT's How To Make Almost Anything which I also explained a bit here in this thread. Like I mentioned there, I got it working with the MIT code, and now have a basic sketch that works for my original board, where I define the pins like this.

#define SCL_pin (1 << PB0)
#define SCL_pins PINB
#define SCL_port PORTB
#define SCL_direction DDRB
#define SDA_pin (1 << PB1)
#define SDA_pins PINB
#define SDA_port PORTB
#define SDA_direction DDRB

UNFORTUNATELY, I designed and fabricated a new board where the SCL and SDA pins are now PA3 and PA2 respectively. I tried to adjust the sketch by changing the defines to all be PORTA, DDRA, etc like this:

#define SCL_pin (1 << PA3)
#define SCL_pins PINA
#define SCL_port PORTA
#define SCL_direction DDRA
#define SDA_pin (1 << PA2)
#define SDA_pins PINA
#define SDA_port PORTA
#define SDA_direction DDRA

Problem is, the tiny44 ceases to read from the IMU with the new pinout. The input/output functions in the program look like this:

#define output(directions,pin) (directions |= pin) // set port direction for output
#define input(directions,pin) (directions &= (~pin)) // set port direction for input
#define clear(port,pin) (port &= (~pin)) // clear port pin
#define pin_test(pins,pin) (pins & pin) // test for port pin

The pi I am using is getting the initial values of data[], so I know it is communicating fine with the tiny44

I realize the pin mapping changes depending on the core I'm using. I don't think that impacts the way the SDA_pin and SCL_pin are defined, because defining them PB0 and PB1 worked... Plus I tried about every pin name possible.

I have also tried the Damellis and Drazzy cores, and neither is working for me.

I tried using a few BitBang libraries like SoftWire, but with no luck.

I have tried a few boards as well, so I don't think it's hardware related.

I don't know what else to try. Any help would be much appreciated! Thanks!!

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