There is actually a simple method available to tune it, swSerial uses tuned delay and measures elapsed time as clock cycles, so you can also adjust the #define F_CPU 1290000UL I ran the OSCCAL tuner but could not see if it was successful. I only have TX/RX connected (PB1/PB0) nothing elseĪssuming you are using the SM to get a stable connection first, that would mean an Empty sketch on an UNO, and TX->TX and RX<-RX Yes but have you tried something a bit slower just in case On top of that temperature fluctuations can influence the clock speed (don't know how much though)
Yes well basically the ATtiny doesn't have a crystal as a clock but a capacitor-resistor, combo (with drain, sort of like a NE555 setup) and this may not be tuned accurately, which of course for Serial communication is quite relevant. Check OSCCAL (see OSCCAL tuner example).
