如下图所示，请问为什么我改变R12的阻值，无法改变步进电机的电流？The TMC2100 provides the option to eliminate external sense resistors. In this mode the externalsense resistors become omitted (shorted) and the internal on-resistance of the power MOSFETs is used for current measurement (see Figure 4.2). As MOSFETs are both, temperature dependent and subject to production stray, a tiny external resistor connected from +5VOUT to AIN/IREF provides a precise absolute current reference. This resistor converts the 5V voltage into a reference current. Be sure to directly attach BRA and BRB pins to GND in this mode near the IC package. The mode is enabled by tying CFG3 to VCCIO.设计还是建议多看看datasheet，里面说的很清楚，IC保留了固定电流模式，也就是你的原理图的BRA和BRB接地。

这样情况下怎么变电阻也没用。

如图所示