Flashing new firmware on an ATTiny from a Boron?

Hardware
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I am working on a sensor that connects an AtTiny MCU to a Boron and communicates using the OneWire protocol. So far that’s working fine. With the newer generation of ATTiny chips, they can be programmed over a single pin (UPDI).

My sensor will essentially interface an I2C sensor to my Boron based device, communicating with it via OneWire. I already have OneWire working on the Boron with DS18B20 slaves.

My question is, “Is anyone else doing something similar, with an ATTiny or other micro sitting in between their particle device and the actual sensor?” I normally only use OneWire protocol to communicate with my sensors, but I’m thinking about how I might be able to actually update the firmware in the “adapter” micro over the air. What I’m thinking is that I send the firmware to the Boron OTA (<8KB so I can store it in RAM), switch to a UPDI programming routine and use the pin I normally use for OneWire communications to reprogram the ATTiny1614 at the other end. This of course is assuming I connect the OneWire pin from the Boron to the UPDI/RESET pin on the ATtiny1614, which is entirely doable. Electrically the connection for a OneWire slave and UPDI programming pin are identical, each requiring a ~4.7K pullup resistor.

This is something I am going to experiment with, but I am curious if anyone has attempted something similar.

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I’m still thinking about possibilities, and I’m still learning about the flashing process of the new gen of ATtiny’s. It looks like though do flash with just power, ground, and UPDI/RESET I need to first pule it with 12VDC. There might be another way that I’m not aware of using a bootloader though. If the 12V pulse is required I’ll have to think pretty hard about whether I’m going to add an LDO and a few analog switch ICs to my board.

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