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Serial Read

Read data from serial port

Since R2020b

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  • NVIDIA Serial Read block

Libraries:
NVIDIA Jetson and NVIDIA DRIVE / Communication

Description

Use the Serial Read block to read data from a serial device connected to a NVIDIA® Jetson™ board.

To open the serial pin map on the NVIDIA Jetson board, click the View pin map button. For more information, see Serial Port Mapping for NVIDIA Jetson Boards.

During Monitor and Tune, the block outputs results from the executable running on the target hardware. During simulation in all other modes, the block outputs zeroes.

You can choose to read the data in the blocking or the nonblocking mode. For more information, see Partially receive data from serial port and Receive data from serial port

Examples

Read and Write Data over Serial Port on NVIDIA Jetson Platforms

Read and Write Data over Serial Port on NVIDIA Jetson Platforms

Use MATLAB® Coder™ Support Package for NVIDIA® Jetson® and NVIDIA DRIVE® to read and write serial data over the UART port on a Jetson board.

Ports

Output

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The data port through which the block reads the data from the serial device.

Data Types: single | double | int8 | int16 | int32 | uint8 | uint16 | uint32

This output port shows the status of the read data. This table lists the possible status values and their description.

Status ValueStatus Description
0SUCCESS
1RX_BUSY
2TX_BUSY
4PARITY_ERROR
8FRAME_ERROR
16BUS_ERROR
32DATA_NOT_AVAILABLE

Dependencies

This output port is available only if the Output partially received data option is not selected.

Data Types: uint8

The Length port outputs the number of data bytes in the received message.

Dependencies

This output is available only if the Output partially received data option is selected.

Data Types: uint8

Parameters

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Main Tab

The port at which you connect the NVIDIA Jetson board to the serial device.

Select the rate at which the data is read over the serial line. The baud rate is measured as the number of bits read per second.

Select the parity you want to add to the transmitted data. A parity bit is used to detect error in the data transmission.

  • None – This value means that no parity is used for error detection in the data transmission.

  • Even – The parity bit value is 1 if the number of bits with value 1 is odd. The parity bit value is 0 if the number of bits with value 1 is even.

  • Odd – The parity bit value is 1 if the number of bits with value 1 is even. The parity bit value is 0 if the number of bits with value 1 is odd.

Select the number of bits used to signal the stop of data transmission.

Enter the data size of the data that you want to read from the serial device for the selected data type.

Select the data type you want to read.

Specify how often the block should read the serial data. Enter a value greater than zero.

Advanced Tab

  • on — When you select this parameter, the read operation runs in the Blocking mode. The read operation is blocked while waiting for the requested data to be available. If data is available, the Data port outputs data. If data is not available, the Data port waits for data.

    A task overrun occurs if the target hardware is still waiting for the data to be available when the next read operation is scheduled to begin.

    To fix overruns:

    • Increase the time step by using the Sample time parameter.

    • Reduce the length of data requested by using the Data length (N) parameter.

  • off — When you clear this parameter, the read operation runs in the Non-blocking mode. When reading data, if data is not available, the Data port outputs zeroes. The Status port outputs 32, indicating that no new data is available.

Specify the amount of time that the block should wait for the data during each time step if the Wait until data received parameter is selected. If timeout occurs, the read operation is aborted.

Dependencies

To enable this parameter, select Wait until data received parameter.

  • on — When you select this parameter, the Data port outputs partially received data at the sample time.

  • off — When you clear this parameter, the Data port outputs zeros at every sample time till the requested number of data elements is received.

Dependencies

To enable this parameter, select the Wait until data received parameter (nonblocking mode). For more information, see Partially receive data from serial port.

Partially receive data from serial port

This section describes the values at the Length output port when the length of the messages received is less than, greater than, or equal to the length of the requested data. This section explains the values at the output ports with the Data type set to uint8 and the Data size (N) set to 4 in nonblocking mode with the Output partially received data parameter selected.

  • Length of data received = Data length (N): The Data port outputs the message as a data vector of the size specified in the Data size (N) parameter.

    Suppose that the Data size (N) parameter specified is 4 and the length of the message received is also 4.

    In this case, the Data port outputs a data vector of size 4 filled with the data bytes of the message and the Length port outputs 4.

    Receive buffer when length of data received is equal to value specified for data size N

  • Length of data received < Data length (N): The Data port outputs the message as a data vector of the size specified in the Data size (N) parameter. All the empty spaces in the vector are filled with zeroes.

    Suppose that the Data size (N) parameter specified is 4 and the length of data received is 3 bytes.

    In this case, the Data port outputs a data vector of size 4. The first three data bytes in the vector are the bytes from the received message and the remaining space is filled with zero. The Length port outputs 3.

    Receive buffer when length of data received is less than the value specified for data size N. Space in buffer filled with zeros

  • Length of data received > Data length (N): The Data port outputs a data vector of the size specified in the Data size (N) parameter. The vector contains only the first N data bytes from the message. The remaining data bytes are left in the buffer.

    Suppose that the Data length (N) parameter specified is 4 and the length of data received is 5 bytes. In this case, the port outputs a data vector of size 4. The vector contains only the first 4 bytes from the received data. The remaining data byte is left in the buffer. The Length port outputs 4.

    Receive buffer when length of data received is greater than the value specified for data size N. Additional data left in buffer

Receive data from serial port

This section describes the values at the Status output port when the length of the messages received is less than, greater than, or equal to the length of the requested data. This section explains the values at the output ports with Data type set to uint8 and Data size (N) set to 4 in blocking and nonblocking modes.

  • Length of data received = Data length (N): The Data port outputs the message as a data vector of the size specified in the Data size (N) parameter.

    Suppose that the Data size (N) parameter specified is 4 and the length of the message received is also 4.

    In this case, for both blocking and nonblocking modes, the Data port outputs a data vector of size 4 filled with the data bytes of the message, and the Status port outputs 0.

    Receive buffer when length of data received is equal to value specified for data size N

  • Length of data received < Data length (N): The Data port outputs the message as a data vector of the size specified in the Data size (N) parameter. All the empty spaces in the vector are filled with zeroes.

    Suppose that the Data size (N) parameter specified is 4 and the length of data received is 3 bytes.

    For nonblocking mode, the Data port outputs a data vector of size 4. The first three data bytes in the vector are the bytes from the received message. The remaining space is filled with zero. The Status port outputs 1.

    For blocking mode, the block waits until all the data bytes are received within the time specified in the Timeout parameter. If the fourth data byte is not received before timeout, the Data outputs zeroes and the Status port outputs 1. The three received data bytes are left in the buffer.

    Receive buffer filled with zeros till all data bytes received

  • Length of data received > Data length (N): The Data port outputs a data vector of the size specified in the Data size (N) parameter. The vector contains only the first N data bytes from the message. The remaining data bytes are left in the buffer.

    Suppose that the Data length (N) parameter specified is 4 and the length of data received is 5 bytes. In this case, for both blocking and nonblocking modes, the port outputs a data vector of size 4. The vector contains only the first 4 bytes from the received data. The remaining data byte is left in the buffer. The Status port outputs zero.

    Receive buffer when length of data received is greater than the value specified for data size N. Additional data left in buffer

Version History

Introduced in R2020b