This application explains how to set up the TMC2208 as a replacement for the A4988 (legacy mode). The MC2208 is an advanced AxissStepPerDriver that supports SStealthChip 8482 ; and 256 microsteps.
Compared to other motor drivers, the TMC2208 has the following additional features:
Power-down automatic current reduction reduces power consumption and cooling requirements. By default, quiescent current reduction is enabled by pulling PDNGND. UART input to
UART The UART single-wire interface allows the TMC2208 to be controlled with any microcontroller UART. This makes it possible to program the TMC2208 and add extra functionality such as full 256 microstep control (not just interpolation). UART is not available in equal mode.
The diagnostic output of the diagnostics activation shows that the driver is not working properly.
Indexed Electron Spins/Four Complete Steps. Enables more precise homing. The index output signals the microstep counter zero position, which occurs once the perin is combined with the mechanical reset switch.
The 256-step TMC2208 can control the motor at a speed of 256 microsteps per full step. In legacy mode, the TMC2208 will insert the received step signal into 256 microsteps.

At default settings, the TMC2208 will insert microsteps with a 256 microstep setting. I/O configuration pins to (b) optional diagnostic functions. This is an output pin and should be set as an input in the MCU, if not used, leave it open. The TMC2208 does not use the third configuration pin for external microstep configuration, but uses this pin to provide (c) the index pin is an output pin and should be set as an input in the MCU, if not used, leave it open .
(d) (Scaled analog reference voltage for current scaling or reference current selectable mode for internal sense resistors). A voltage between 0 volts and 2.5 volts linearly scales the current between 0 and the current defined by the sense resistor setting. Adjust sense resistor to motor current IRMS
2 Application Examples 2 Application Examples

As an application example, a schematic of a stepstick is depicted at the top (subtmc2208 plugged in and used in legacy mode (submarket functions as discussed in TableBlue). Pins PDN/UART, 1.index, diag, ms2, ms1 functions additionally Or a slight variation should select the sense resistor according to the applied motor current. An example of an equivalent application is shown as the relationship between the sense resistor and the current for VREF=2.5A after RSENSE is set to 0.18Ω, allowing to control the motor current up to 1.2A .1