Hi all,
I have quite successfully created a motorcycle speedometer using a digispark (attiny85 & micronucleus), hall sensor, X27 stepper and a microstepping driver. Even managed to fit a tiny i2c oled which serves as voltmeter or tripmeter. Software written from scratch after reading through many code samples. If someone ist interested I can provide more details as code, pcb and such.
Worked for nearly a year without issues (after I fitted better spark plugs).
Since last weekend the speedo suddenly shows the speed much to fast, roughly real speed x 1.5 (driving 80km/h - show 120 km/h). Started after the black headlight with the speedo baked in the sun for quite a while getting really hot but this stuck even after cooling down. Run fine for a while, getting faster over time until it reaches the x1.5
As the code counts the signal from the hall sensor over a fixed period of time to calculate the speed my guess is that the timer is messed up and/or the attiny running on another clock setting as expected. Voltage regulator which provides the 5V may be messed up but the unit is still running except beeing the speed to fast.
I am using the internal timer as I couldnt spare the pins for an external crystal and this setup worked fine for quite a long time.
I guess I could just swap out the digispark but I would like to know what happened. Any idea where to start looking?
Thanks a lot!