TMC2041 DATASHEET (Rev. 1.02 / 2017-MAY-16)
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read only. Some of the registers allow both read and write access. In case read-modify-write access is
desired for a write only register, a shadow register can be realized in master software.
1.2.1 SPI Interface
The SPI interface is a bit-serial interface synchronous to a bus clock. For every bit sent from the bus
master to the bus slave another bit is sent simultaneously from the slave to the master.
Communication between an SPI master and the TMC2041 slave always consists of sending one 40-bit
command word and receiving one 40-bit status word.
The SPI command rate typically is a few commands per complete motor motion.
1.2.2 UART Interface
The single wire interface allows differential operation similar to RS485 (using SWIOP and SWION) or
single wire interfacing (leaving open SWION). It can be driven by any standard UART. No baud rate
configuration is required. An optional ring mode allows chaining of slaves to optimize interfacing for
applications with regularly distributed drives.
1.3 Moving and Controlling the Motor
1.3.1 STEP/DIR Interface
Each motor is controlled by a step and direction input. Active edges on the STEP input can be rising
edges or both rising and falling edges as controlled by another mode bit (DEDGE). Using both edges
cuts the toggle rate of the STEP signal in half, which is useful for communication over slow interfaces
such as optically isolated interfaces. On each active edge, the state sampled from the DIR input
determines whether to step forward or back. Each step can be a fullstep or a microstep, in which
there are 2, 4, 8, 16, 32, 64, 128, or 256 microsteps per fullstep. During microstepping, a step impulse
with a low state on DIR increases the microstep counter and a high decreases the counter by an
amount controlled by the microstep resolution. An internal table translates the counter value into the
sine and cosine values which control the motor current for microstepping.
1.4 stallGuard2 – Mechanical Load Sensing
stallGuard2 provides an accurate measurement of the load on the motor. It can be used for stall
detection as well as other uses at loads below those which stall the motor, such as coolStep load-
adaptive current reduction. This gives more information on the drive allowing functions like
sensorless homing and diagnostics of the drive mechanics.
1.5 coolStep – Load Adaptive Current Control
coolStep drives the motor at the optimum current. It uses the stallGuard2 load measurement
information to adjust the motor current to the minimum amount required in the actual load situation.
This saves energy and keeps the components cool.
Benefits are:
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Energy efficiency
Motor generates less heat
Less or no cooling
power consumption decreased up to 75%
improved mechanical precision
improved reliability
Use of smaller motor
less torque reserve required → cheaper motor does the job
Figure 1.2 shows the efficiency gain of a 42mm stepper motor when using coolStep compared to
standard operation with 50% of torque reserve. coolStep is enabled above 60RPM in the example.
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TRINAMIC [ TRINAMIC MOTION CONTROL GMBH & CO. KG. ]
