I am using the Arduino UNO and SPI to program a ATtiny84 on a breadboard. My ATtiny is using the I2C interface to communicate with a real-time clock chip. My problem is that I have to disconnect the ISP programming pins from the Arduino to the ATtiny to allow I2C to work.
I want to build a shield that I can plug into UNO and program the ATtiny (instead of breadboard) and leave the shield in place, for power etc, and still have the I2C interface work. Not sure I am explaining this right but I am looking for the best way to isolate the programming pins from the UNO, so that I can run the ATtiny in-circuit.
It takes 4 pins to ISP program an ATTiny, so I could possible have a slider switch that I could switch over to disconnect the 4 pins after programming, but is there a better way or a more “electronic” way with a tact switch to isolate the pins.
Phew… Hope I am making sense.