Table 99. Counting Direction Versus Encoder Signals - ST STM32F412 Reference Manual

Advanced arm-based 32-bit mcus

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

the incremental 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

An external incremental encoder can be connected directly to the MCU without external

interface logic. However, comparators are normally be used to convert the encoder's

differential outputs to digital signals. This greatly increases noise immunity. The third

encoder output which indicate the mechanical zero position, may be connected to an

external interrupt input and trigger a counter reset.

direction control. It also shows how input jitter is compensated where both edges are

selected. This might occur if the sensor is positioned near to one of the switching points. For

this example we assume that the configuration is the following:

CC1S= '01' (TIMx_CCMR1 register, TI1FP1 mapped on TI1)

CC2S= '01' (TIMx_CCMR2 register, TI2FP2 mapped on TI2)

CC1P= '0', CC1NP = '0', IC1F ='0000' (TIMx_CCER register, TI1FP1 noninverted,

CC2P= '0', CC2NP = '0', IC2F ='0000' (TIMx_CCER register, TI2FP2 noninverted,

SMS= '011' (TIMx_SMCR register, both inputs are active on both rising and falling

CEN = 1 (TIMx_CR1 register, Counter is enabled)

Table 99. Counting direction versus encoder signals

Level on opposite

signal (TI1FP1 for

TI2, TI2FP2 for TI1)

gives an example of counter operation, showing count signal generation and

RM0402 Rev 6

General-purpose timers (TIM2 to TIM5)

TI1FP1 signal

TI2FP2 signal

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