Klipper 的 TMC 驅動設定

很辛苦的把舊的 3D 印表機改成 TMC2209 的靜音驅動，發現 microstep 仍然只能設到 16，噪音無法減少多少，有點失望。

不想換主板，因為這台機器會不會繼續用都不確定，因為已有太多機器了。只好細讀相關資料，看能有多大的改善。

MCU 是 ATmega2560，調到 64 microstep，一執行 home 功能，就出現像上面的錯誤。

TMC2209 靜音驅動的考量

參考 TMC drivers。

• StealthChop：是一种使用 PWM 电压而不是电流来驱动电机的技术。结果在低速时几乎听不见。StealthChop 具有较低的步进速度限制，如果您需要更快地移动，您可能需要使用 spreadCycle 或配置混合模式。
• SpreadCycle：是另一种步进模式。驱动器将使用四个阶段将所需的电流驱动到步进电机中。SpreadCycle 提供更大的扭矩。缺点是噪音水平略高。

兩種模式不要混用。低速時用 StealthChop，安靜。高速時用 SpreadCycle，較有力，較吵。

8 位元 CPU，如 Atmega2560，microstep 只能設到 16。使用 TMC 驅動的好處，是能透過 interpolation 降低噪音。但是 Klipper 的指引建議關閉 interpolation，使用 spreadCycle 或 stealthChop，其中 spreadCycle 為優先。截錄說明如下

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The TMC driver interpolate setting may reduce the audible noise of printer movement at the cost of introducing a small systemic positional error. This systemic positional error results from the driver's delay in executing "steps" that Klipper sends it. During constant velocity moves, this delay results in a positional error of nearly half a configured microstep (more precisely, the error is half a microstep distance minus a 512th of a full step distance). For example, on an axis with a 40mm rotation_distance, 200 steps_per_rotation, and 16 microsteps, the systemic error introduced during constant velocity moves is ~0.006mm.

For best positional accuracy consider using spreadCycle mode and disable interpolation (set interpolate: False in the TMC driver config). When configured this way, one may increase the microstep setting to reduce audible noise during stepper movement. Typically, a microstep setting of 64 or 128 will have similar audible noise as interpolation, and do so without introducing a systemic positional error.

If using stealthChop mode then the positional inaccuracy from interpolation is small relative to the positional inaccuracy introduced from stealthChop mode. Therefore tuning interpolation is not considered useful when in stealthChop mode, and one can leave interpolation in its default state.

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