Documentation

Encoder Input

Connect to and read from encoder input channels

Library

Simulink® Desktop Real-Time™

Description

Connect to and read from specific encoder input channels into your Simulink model. After you have added an Encoder Input block to your model, you can enter the parameters for its I/O driver.

Parameters

Install new board

Click this button to register a board with Simulink Desktop Real-Time.

When you click Install new board, the software displays a list of manufacturers of supported boards. When you select a manufacturer, the software displays a list of boards available from that manufacturer. When you select a board, the software adds the board to the list of registered boards and makes that board the current board.

By default, the initial selection in the list of registered boards is < no board selected >. When you select a board in the list, the Delete current board and Board setup buttons become active.

Delete current board

Click this button to delete the current board. The initial selection of the list of registered boards changes to < no board selected >, and the Delete current board and Board setup buttons become inactive.

Board setup

Click this button to set up the board.

A board-specific dialog box opens for you to use to set up the board. For more information to set up the board, see the board manufacturer documentation.

Sample time

Enter a value representing how frequently you want the block to execute and interact with the I/O hardware. The block also synchronizes your model with the real-time clock at this sample rate.

    Tip   If you are using a fixed-step solver, you must enter the value that you entered in the Fixed step size box in the Configuration Parameters dialog box, or an integer multiple of that value.

Maximum missed ticks

In Normal Mode, enter the number of timer ticks that your model can lag behind the real-time kernel. When the model lags by this number or less, the software assumes that the lag is temporary and allows the model to catch up, even if the model misses some ticks. When the model lags by more than this number, the software reports an error and simulation stops.

In External Mode, the software ignores this value.

Show "Missed Ticks" port

In Normal Mode, select this check box to display the number of missed ticks as a block output.

In External Mode, The "Missed Ticks" port displays zero.

Yield CPU when waiting

In Normal Mode, select this check box to grant other programs more CPU time while the kernel waits for a response from the hardware.

In External Mode, the software ignores this value.

Input channels

Enter a channel vector that selects the encoder input channels that you are using on this board. The vector can be any valid MATLAB® vector form. For example, to select the first four encoder input channels, enter:

[1,2,3,4] or [1:4]
Quadrature mode

Encoders use two sets of stripes, shifted in phase, to optically detect the amplitude and direction of movement. This parameter specifies which encoder stripe edges the encoder should count. From the list, select:

  • single — Counts the rising edges from one stripe set.

  • double — Counts the rising edges from both stripe sets.

  • quadruple (default) — Counts rising and falling edges from both stripe sets.

Quadruple mode yields four times more pulses per revolution than the single mode. Therefore, quadruple is more accurate. Use quadruple mode unless other parameters dictate otherwise.

Reset input function

The encoder interface chip has a reset pin in addition to encoder inputs. In most cases, you connect this pin to the index output of the encoder. However, you can connect it to any signal or not at all. This parameter specifies the function of this pin. From the list, select:

  • gate — Enables encoder counting.

  • reset — Level reset of the encoder count.

  • rising edge index — Resets the encoder count on the rising edge.

  • falling edge index — Resets the encoder count on the falling edge.

Input filter clock frequency

The encoder interface chip has a built-in low-pass filter that attempts to filter out high frequencies, which are interpreted as noise. This parameter is the cutoff frequency (Hz) of this filter. The cutoff frequency that you specify is rounded to the nearest frequency supported by the chip.

If the encoder is moving slowly and high-frequency noise is present, use the filter to eliminate the noise. With the filter in operation, the chip does not count the noise as encoder pulses. If the encoder is moving quickly, the filter can filter out the high-frequency pulses, including those that you want to count. In this case, consider disabling the filter by setting the cutoff frequency to Inf.

Output data type

From the list, select the type of data that the block outputs to the model.

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