perf(axis): replace int64_t with int32_t in torque pipeline for Cortex-M4 efficiency

The torque values in the FFB pipeline are bounded to [-32767, 32767], making
int64_t unnecessary throughout. Replacing with int32_t matches the native
register width of the Cortex-M4 and avoids 64-bit software emulation overhead.

Functions updated: setFfbEffectTorque, updateTorque, applyTorqueSlewRateLimiter,
applySpeedLimiterTorque. Member ffbEffectTorque also reduced to int32_t.
No logic change.

Author: manoukianv

Firmware/FFBoard/Inc/Axis.h

@@ -342,7 +342,7 @@ class Axis : public PersistentStorage, public CommandHandler, public ErrorHandle
 	 * @brief Calculates the FFB torque exponential torque, from the input torque and apply expo and scaler
 	 * @return The calculated exponential torque.
 	 */
-	int32_t calculateFFBTorque();
+	int64_t calculateFFBTorque();
 
 	/**
 	 * @brief Starts a force fade-in.
@@ -412,7 +412,7 @@ class Axis : public PersistentStorage, public CommandHandler, public ErrorHandle
 	 */
 	void setExpo(int val);
 
-	float calculateExpoTorque(float torque);
+	int32_t calculateExpoTorque(int32_t torque);
 	/**
 	 * @brief Applies the speed limiter PI controller to the torque.
 	 * @param torque A reference to the torque value to be modified.

Firmware/FFBoard/Src/Axis.cpp

@@ -694,32 +694,35 @@ uint16_t Axis::getPower(){
 /**
  * Calculates an exponential torque correction curve and scale for FFBEffect
  */
-float Axis::calculateExpoTorque(float torque){
-	float torqueSign = torque > 0 ? 1.0f : -1.0f;
-	torque = powf(fabsf(torque), expo) * torqueSign;
-	return torque;
+int32_t Axis::calculateExpoTorque(int32_t torque){
+	float torquef = (float)torque / (float)0x7fff; // This down and upscaling may introduce float artifacts. Do this before scaling down.
+	if(torquef < 0){
+		return -powf(-torquef,expo) * 0x7fff;
+	}else{
+		return powf(torquef,expo) * 0x7fff;
+	}
 }
 
-int32_t Axis::calculateFFBTorque(){
+int64_t Axis::calculateFFBTorque() {
 
-	// 1. Initial conversion and normalization
-	// Convert to float and move to [-1.0, 1.0] range immediately.
-	float torque = (float)this->ffbEffectTorque * (1.0f / 32767.0f);
+	int64_t torque = this->ffbEffectTorque;
 
-	// 2. Game Clipping detection
-	// Performed on normalized value for consistency.
-	if(fabsf(torque) >= 1.0f){
+	// 1. Game Clipping detection
+	// If the game sends more than the theoretical maximum (+/- 32767), the signal is clipped at the source.
+	if(abs(torque) >= 0x7fff){
 		pulseClipLed(); // Visual alert: game signal is clipping
 	}
 
-	// 3. Apply Expo (Linearization or sensation curve)
-	if(expo != 1.0f){
+	// 2. Apply Expo (Linearization or sensation curve)
+	if(expo != 1){
 		torque = calculateExpoTorque(torque);
 	}
 
-	// 4. Final scaling and single conversion back to integer
-	// Apply both the FFB range and the effect ratio in one final step.
-	return (int32_t)(torque * 32767.0f * effectRatioScaler);
+	// 3. Game specific gain (effectRatioScaler)
+	// Scale the FFB from game only (allows lowering game effects without lowering endstops)
+	torque = (int64_t)((float)torque * effectRatioScaler);
+
+	return torque;
 }
 
 int32_t Axis::getTorque() { return metric.current.torque; } // Fix: move from previous to current
@@ -818,8 +821,8 @@ void Axis::applyTorqueSlewRateLimiter(int32_t& torque)
 {
 	// Limits the rate of change of the torque (slew rate), to smooths out sudden changes in torque.
 	// Essential for a natural feel and to prevent "clanking" noises.
-	if (maxTorqueRateMS <= 0) {
-		return;
+	if(maxTorqueRateMS == 0) {
+		return; // Limiter is disabled
 	}
 
 	// This prevents sudden torque jumps, resulting in a smoother feel.