Working on an ICOM CI-V to Yaesu BCD band decoder using an Arduino UNO, planning to port it to ATTiny84. The sketch reads ICOM CI-V data, parses the frequency, and converts it to Yaesu BCD band data for my Quadra amplifier. The project requires either an ICOM CT-17 CI-V level converter or a homebrew CI-V level converter. Having trouble with the level conversion - getting intermittent frequency decoding especially on 20m. Using the 7404 hex inverter level converter instead of the transistor assembly, which should provide cleaner signal inversion. Anyone else run into timing issues with CI-V parsing on ATTiny? The Arduino UNO version works flawlessly but the ATTiny port seems more sensitive to bus collisions.

I had similar issues with CI-V timing on smaller micros. Try adding pull-up resistors on the CI-V line and increase your parsing buffer size. The ATTiny runs at a different clock speed which can affect serial timing.

Make sure you have 'CI-V transceive' enabled in your TRX settings and consider implementing a state machine for collision protection. I've seen bus conflicts cause exactly the symptoms you describe.

Check your baud rate settings and add some delay between CI-V message processing. The watchdog timer can help if you're missing input data - set it to about 10 seconds to reset relays if CI-V goes quiet.