DEC - Angle decoder input

Imperix controllers provide angle decoder (DEC) resources to decode quadrature-encoded signals produced by incremental encoders, which are widely used in motor drive applications. At the hardware level, DEC inputs are available on pins that are shared with GPI pins.

These inputs can be configured as either four independent inputs or two differential DEC inputs. Each decoder module counts all 4 edges of the A and B inputs, resulting in an angular resolution that is 4 times higher than the PPR value usually specified for a given encoder. The position counter can be reset either to a specified value or using the sensor’s Z signal. The decoded position is latched simultaneously to ADC inputs.

Practical advice for using the DEC modules is provided in PN104.

Simulink block

Signal specification

• The output signal is the decoded angle in radians.
• The sim input signal is used in simulation and represents the actual angle value in radians, computed by the simulation plant model.
• The > input signal needs to be connected to the CONFIG block to account for the exact sampling instant in simulation.

Parameters

• Device ID selects which B-Box/B-Board to address when used in a multi-device configuration
• Input mode selects if the decoder considers one GPI input per encoder signal (Single-ended) or two GPI with complementary signals (Differential).
• DEC module selects which GPI inputs are used. See the B-Box datasheet or B-Board datasheet to check where to connect the encoder signals.
• Pulses per rotation defines the number of pulses of the A or B signal per complete rotation of the encoder, as specified by the manufacturer.
• Reset mode selects the counter reset mode. If Z input is selected, the pulse counter value is reset on the rising edge of the Z signal. If the maximum value is selected, it is reset as soon as it reaches the number of pulses per rotation.
• Direction defines when A is leading B, if the angle increases (Clockwise) or decreases (Counterclockwise).
• Invert input signals configures the decoder to consider the inverted logical value of the considered GPI inputs.

PLECS block

Signal specification

• The output signal is the decoded angle in radians.
• The target inport (only visible at the atomic subsystem level) is used in simulation and represents the actual angle value in radians, computed by the simulation plant model.
• The > input signal needs to be connected to the ADC output of the CONFIG block to account for the exact sampling instant in simulation.

Parameters

• Device ID selects which B-Box/B-Board to address when used in a multi-device configuration
• Input mode selects if the decoder considers one GPI input per encoder signal (Single-ended) or two GPI with complementary signals (Differential).
• DEC module selects which GPI inputs are used. See the B-Box datasheet or B-Board datasheet to check where to connect the encoder signals.
• Pulses per rotation defines the number of pulses of the A or B signal per complete rotation of the encoder, as specified by the manufacturer.
• Reset mode selects the counter reset mode. If Z input is selected, the pulse counter value is reset on the rising edge of the Z signal. If the maximum value is selected, it is reset as soon as it reaches the number of pulses per rotation.
• Direction defines, when A is leading B, if the angle increases (Clockwise) or decreases (Counterclockwise).
• Invert input signals configures the decoder to consider the inverted logical value of the considered GPI inputs.

C++ functions

void Dec_ConfigureInputMode(tDecChannel channel, tDecInputMode inputMode, unsigned int device=0);Code language: C++ (cpp)

void Dec_ConfigurePulsePerRotation(tDecChannel channel, unsigned int pulsePerRotation, unsigned int device=0);Code language: C++ (cpp)

void Dec_ConfigureResetMode(tDecChannel channel, tDecResetMode resetMode, unsigned int device=0);Code language: C++ (cpp)

void Dec_ConfigureResetPerRotation(tDecChannel channel, unsigned int resetPerRotation, unsigned int device=0);Code language: C++ (cpp)

void Dec_ConfigureDirection(tDecChannel channel, tDecDirection direction, unsigned int device=0);Code language: C++ (cpp)

void Dec_ConfigureInputPolarity(tDecChannel channel, tDecPolarity polarity, unsigned int device=0);Code language: C++ (cpp)

float Dec_GetAngle(tDecChannel channel, unsigned int device=0);Code language: C++ (cpp)