The delay, in milliseconds, depends on the rotational speed of theengine. A fixed delay of 5ms is easy to implement, but would that besufficient? Wouldn't it be easier to adjust the sensor so that thisdelay isn't needed, and only advance the ignition in software once theengine has started?

What I would like to change about the existing design, is to connect the hall sensor to pin 9 instead of pin 7, the SCR to pin 2 instead of pin 6, and move the jumpers on pins 7 and 8 to two other pins, probably 17 and 18, to be able to use the UART for communication with a PC or laptop for configuration and debugging.

While I´m not thrilled about the design, in particular, the (in my opinion) unnecessary optocoupler, the rather fragile flyback converter, and the use of a 7805 voltage regulator instead of a low-drop regulator or shunt regulator.

But by far the worst part is the rather poor choice of the I/O pins of the microcontroller, which makes it impossible to use any of the specialized peripherals.

I don't mean to offend anyone by saying this, but I feel it needs to be said to be able to explain what I would like to change, and why. <br type="_moz"/>