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Fix PCA9685 V2 driver: PWMTO fading logic and overflow (#24159)

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Fixed integer overflow causing loops when dimming down. Corrected step calculation for smooth fading with LEDs.
NOT tested with servos!
This commit is contained in:
Sven H.
2025-11-25 11:51:07 +01:00
committed by GitHub
parent 73fd0aa377
commit 9b7ded2343
1 changed files with 46 additions and 27 deletions
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73
tasmota/tasmota_xdrv_driver/xdrv_15_pca9685_v2.ino
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@@ -285,18 +285,33 @@ void PCA9685_RunMotor()
if (m->step == 0 || (m->step % m->every == 0))
{
// AddLog(LOG_LEVEL_DEBUG, "PCA9685: MOTOR dev=%u pin=%u s=%u e=%u pwm=%lu target=%lu dir=%d",
// dev,
// pin,
// m->step,
// m->every,
// m->pwm,
// m->target,
// m->direction);
// --- SECURITY-FIX START ---
// We temporarily use "int32_t" (signed and large enough)
// so that we don't run into overflows.
int32_t next_val = (int32_t)m->pwm + (int32_t)m->direction;
PCA9685_SetPWM(dev, pin, m->pwm + m->direction, pca9685.inverted[dev]);
// we dim UP (direction > 0)
if (m->direction > 0) {
// // If we overshoot the target -> clamp to the target
if (next_val > m->target) next_val = m->target;
// Absolute hardware upper limit (4096 is the “fully on” bit)
if (next_val > 4096) next_val = 4096;
}
// we dim DOWN (direction < 0)
if (m->direction < 0) {
// If we were to fall below the target -> clamp to the target
if (next_val < m->target) next_val = m->target;
// Absolute lower limit
if (next_val < 0) next_val = 0;
}
// Now write the safe, verified value
PCA9685_SetPWM(dev, pin, (uint16_t)next_val, pca9685.inverted[dev]);
// --- SECURITY-FIX END ---
}
m->step++;
}
}
@@ -441,24 +456,28 @@ bool PCA9685_Command(void)
// m->target,
// m->direction);
m->every = 0;
while (m->every < 1)
{
uint16_t stepValue = abs((int16_t)m->pwm - (int16_t)m->target) / abs(m->direction);
if (stepValue < 1)
{
m->direction += m->target < m->pwm ? -1 : 1;
continue;
}
// calculate total difference (e.g. 4095 steps)
uint16_t totalSteps = abs((int16_t)m->pwm - (int16_t)m->target);
// calculate how many 50ms-ticks we have at all
// tids is in 0.1s. so tids * 2 is the amount of 50ms ticks.
uint16_t totalTicks = tids * 2;
m->every = round((tids * 200) / stepValue);
if (m->every < 1)
{
m->direction += m->target < m->pwm ? -1 : 1;
continue;
}
if (totalTicks < 1) totalTicks = 1; // lowest possible
// calculate steps per tick
uint16_t stepsPerTick = totalSteps / totalTicks;
if (stepsPerTick < 1) {
// Slow fade (we have morew time than steps)
m->direction = m->target < m->pwm ? -1 : 1;
m->every = totalTicks / totalSteps;
} else {
// Fast Fade (LED Mode: We need to make big steps)
m->direction = (m->target < m->pwm ? -1 : 1) * stepsPerTick;
m->every = 1; // Fire every tick!
}
m->running = true;
}
}
@@ -622,4 +641,4 @@ bool Xdrv15(uint32_t function)
}
#endif // USE_PCA9685_V2
#endif // USE_IC2
#endif // USE_IC2