In-breadboard programming of ATTiny85

I have found a good use for an ATTiny85, which I have never used before. I notice that all of the programmers I've seen, including the Arduino ATTiny programming setup, seem to require that I program the chip essentially out-of-circuit, unlike a Nano, which I can plug into a breadboard circuit and still program in place.

So I am thinking of building a little board into which I socket an ATTiny, then passing the pins through the board so that the ATTiny pins can simultaneously be plugged into my breadboard. For programming, I thought I'd try passing the programming signals from an Arduino programmer through tri-state buffers mounted on my little socket board. When not programming, I'd set the buffer outputs to high impedance.

Does anybody out there know of good reason why this would not work? Thanks in advance for any thoughts, pro or con.

Because the ATTiny has so few pins you usually have to use the programming pins as inputs. Then you can’t program the chip while those inputs are connected to your circuit.

You should never connect two outputs together. Your programmer and your final circuit both have outputs that want to connect to the same pin.

It would seem that if I put tristate buffers on both sides of the pins, i.e., I have high impedance to the circuit when programming, and I have high impedance to the programmer when running the circuit, that all would be well. I'm going to give it a try. If it works, I'll put together an instructable.

Usually I just unplug the programmer when not programming it? Or do you want the programmer built in? That would seem to defeat the "tiny" part of attiny...

I generally write code incrementally , so I may sit down and do 15-20 revisions in an hour. Constantly swapping from programmer to circuit strikes me as an irritation. I intend to make a small board with a 8-pin DIP socket for the Tiny, then carry those eight pins out the bottom of my board in DIP configuration with header pins. That way the Tiny will be electrically connected to both the programmer and a breadboard at the same time.

But I will put tristate buffers on each side of the Tiny pins, so I can set either the programmer or the circuit to high impedance. I haven't examined the Arduino programmer code yet, but it's likely that I can operate the tristates directly from the arduino, thereby creating the equivalent of an incircuit programmer for the Tiny.

I've got several hex tristate buffers lying around, so why not try it?

You might be able to control the tristate buffer from the reset signal - reset is held low during all ISP programming operations.