Encoder Interface Mode; Figure 179. Retriggerable One Pulse Mode - ST STM32WL5 Series Reference Manual

Advanced arm-based 32-bit mcus with sub-ghz radio solution

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Advanced-control timer (TIM1)

Encoder interface mode

To select Encoder Interface mode write SMS='001' in the TIMx_SMCR register if the

counter is counting on TI2 edges only, SMS='010' if it is counting on TI1 edges only and

SMS='011' if it is counting on both TI1 and TI2 edges.

Select the TI1 and TI2 polarity by programming the CC1P and CC2P bits in the TIMx_CCER

must be kept low.

The two inputs TI1 and TI2 are used to interface to a quadrature encoder. Refer to

178. The counter is clocked by each valid transition on TI1FP1 or TI2FP2 (TI1 and TI2

after input filter and polarity selection, TI1FP1=TI1 if not filtered and not inverted,

TI2FP2=TI2 if not filtered and not inverted) assuming that it is enabled (CEN bit in

TIMx_CR1 register written to '1'). The sequence of transitions of the two inputs is evaluated

and generates count pulses as well as the direction signal. Depending on the sequence the

counter counts up or down, the DIR bit in the TIMx_CR1 register is modified by hardware

accordingly. The DIR bit is calculated at each transition on any input (TI1 or TI2), whatever

the counter is counting on TI1 only, TI2 only or both TI1 and TI2.

Encoder interface mode acts simply as an external clock with direction selection. This

means that the counter just counts continuously between 0 and the auto-reload value in the

TIMx_ARR register (0 to ARR or ARR down to 0 depending on the direction). So the

TIMx_ARR must be configured before starting. In the same way, the capture, compare,

repetition counter, trigger output features continue to work as normal. Encoder mode and

External clock mode 2 are not compatible and must not be selected together.

The prescaler must be set to zero when encoder mode is enabled

In this mode, the counter is modified automatically following the speed and the direction of

the quadrature encoder and its content, therefore, always represents the encoder's position.

The count direction correspond to the rotation direction of the connected sensor. The table

summarizes the possible combinations, assuming TI1 and TI2 do not switch at the same

RM0453 Rev 1

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