ESP32 to ATmega328P CDI System – Engine Won’t Start After Switching from Arduino Framework to Pure C

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1

I’ve been working on a CDI (Capacitor Discharge Ignition) system using an ATmega328P (without Arduino bootloader or framework, pure C with register manipulation). It worked fine when using the Arduino framework, but after switching to pure C code, the ignition logic seems to stop working — the engine won't start anymore.
Setup:

  • Microcontroller: ATmega328P @16MHz
  • Trigger: Pulser signal from the engine (digital HIGH pulse)
  • Output: SCR gate control via digital output
  • External serial control from ESP32 via UART

What works:

  • Serial communication between ESP32 and ATmega works fine.
  • I’ve verified trigger pulses are reaching the ATmega (checked with oscilloscope).
  • The code compiles and runs (no infinite loop or reset).

Problem:

  • The SCR never fires, and the engine won’t start.
  • It seems like the timer-based ignition delay logic isn't functioning.
  • I used while(TCNT1 < ...) to implement delay between trigger and spark firing — could this cause the code to hang?
  • I also control limiter and map via serial commands like L0, M1, etc.

Here’s a simplified version of my main ignition loop:

if (PIND & (1 << PD2)) { // Trigger detected
    TCNT1 = 0;
    while (TCNT1 < ignitionDelay); // Wait for specific degrees
    PORTB |= (1 << PB1); // Fire SCR
    _delay_us(100);
    PORTB &= ~(1 << PB1); // Reset output
}

Could the while(TCNT1 < ignitionDelay) be preventing the loop from working properly? Or is there another issue I should be looking into when moving from Arduino to pure C with direct register access?
P.S: I use main(), init(), and sei, not setup and loop

Any advice or tips on debugging this would be greatly appreciated. Thanks in advance!

2

Of course. Did you initialise the timer?