C28x SCI Receive

Receive data on target via serial communication interface (SCI) from host

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Libraries:
C2000 Microcontroller Blockset / C2802x
C2000 Microcontroller Blockset / C2803x
C2000 Microcontroller Blockset / C2805x
C2000 Microcontroller Blockset / C2806x
C2000 Microcontroller Blockset / C280x
C2000 Microcontroller Blockset / C281x
C2000 Microcontroller Blockset / C2833x
C2000 Microcontroller Blockset / C2834x
C2000 Microcontroller Blockset / F280013x
C2000 Microcontroller Blockset / F280015x
C2000 Microcontroller Blockset / F28002x
C2000 Microcontroller Blockset / F28003x
C2000 Microcontroller Blockset / F28004x
C2000 Microcontroller Blockset / F2807x
C2000 Microcontroller Blockset / F2837xD
C2000 Microcontroller Blockset / F2837xS
C2000 Microcontroller Blockset / F2838x / C28x
C2000 Microcontroller Blockset / F28M35x / C28x
C2000 Microcontroller Blockset / F28M36x / C28x
C2000 Microcontroller Blockset / F28p65x
C2000 Microcontroller Blockset / F28p55x

Description

The SCI Receive block supports asynchronous serial digital communication between the processor and other asynchronous peripherals. This block receives scalar or vector data using the specified SCI hardware module.

A model can only contain one SCI Receive block for each module. The C28x processor has four SCI modules — A, B, C, and D. The number of SCI modules available varies depending on the processor selected. You can configure the SCI modules by navigating to Hardware Implementation > Target hardware resources. Verify that these settings meet the requirements of your application.

Note

Serial External mode with similar SCI module blocks results in conflict check error.

The block outputs data either in blocking mode or in non-blocking mode. In blocking mode, the model blocks the execution while it waits for the requested data to be available. In non-blocking mode, the model runs continuously. To set the block in blocking mode, select the Wait until data received option.

Examples

Serial Communication Using SCI Blocks

Use the SCI blocks to set up serial communication between the target hardware and your host computer for C2000™ Microcontroller Blockset.

• Open Model

Closed Loop Control of a DC-DC Buck Converter

Model a closed loop control of a DC-DC buck converter in the C2000™ Microcontroller Blockset. The model runs on a F28379D Launchpad connected to the C2000 digital power supply booster pack.

• Open Model

Field-Oriented Control of PMSM with Quadrature Encoder Using C2000 Processors

Implements the field-oriented control (FOC) technique to control the speed of a three-phase permanent magnet synchronous motor (PMSM). The FOC algorithm requires rotor position feedback, which is obtained by a quadrature encoder sensor. For details about FOC, see Field-Oriented Control (FOC) (Motor Control Blockset).

• Open Model

Ports

Input

Length — Data length received from input port

scalar

The block accepts the length of the data to be received.

Dependencies

To enable this port, set the Data length option parameter to Length via input port.

Data Types: uint8 | uint16 | uint32

Output

Data — Data received from serial bus

scalar | vector

The data received from the serial communication bus.

• The data port is configured as fixed size signal when data length is set to Length via dialog. It outputs only received data.

• The data port is configured as variable size signal when data length is set to Length via Input port or Variable Length. In this case the port outputs received data along with the length of the received data.

  When Data length is set as Variable Length or Length via input port the output data width is 0 if the data is not received. This is independent of connection output type set for Action taken when connection times out parameter.

  In order to generate code for variable size signals, go to Configuration Parameters > Code Generation > Interface and select Variable-size signals. For more information, see

  • Variable-Size Signal Basics

  • Variable-Size Signal Length Adaptation

Note

Currently, Monitor & Tune (External mode) is not supported to output the variable size signal.

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

status — Status of serial communication

scalar

Indicates the status of the received serial data:

• 0 - No errors.

• 1 - A time-out occurred while the block was waiting to receive data. This is the default status if expected header is not received.

• 2 - The received data contains an error (checksum error) or if the required tail is not received.

• 3 - SCI parity error flag: occurs when a character is received with a mismatch.

• 4 - SCI framing error flag: occurs when an expected stop bit is not found.

• 5 - SCI overrun error flag: occurs when a character is transferred to the receive registers before reading the previous character.

• 6 - SCI break-detect flag: occurs when SCI receiver data line (SCIRXD) remains continuously low for at least ten bits.

• 7 - Data not available flag: occurs in non-blocking mode when data is not available in the FIFO. The status is Data not available when the data length is set to Variable length after receiving the header, and if data is not available in the FIFO to read as a data or terminator.

• 8 - Partial Data available: Partial data status represents the data received partially excluding header. The status is set to Partial Data when the data length is set to Variable length, and if the terminator is expected to be received and when not received up to the Max data length.

Dependencies

This port appears only when you select Output receiving status.

Data Types: uint16

Parameters

SCI module — SCI module for communication

A (default) | B | C | D

The SCI module used for communication. The number of SCI modules supported varies across different C2000™ processors.

Additional package header — Indicates start of data

'S' (default) | string | char | number from 0 to 255

The data located at the front of the received data package, which is not part of the data being received, and indicates the start of data. The additional package header must be represented using ASCII characters. You can use a string or a number (0–255). You must add single quotes around strings entered for this parameter, but the quotes are not received or included in the total byte count. To specify a null value (no package header), enter two single quotes only.

The data type of header is not related to the data type mentioned on the block.

Note

• Match additional package headers or terminators with those specified in the host SCI Transmit block.

• If header is empty then whatever present in the receive buffer will be considered as starting point to receive. In case of data length option as Variable length, the tail will be calculated from this starting point itself if header is empty.

• If the expected header is not provided on the block then the data present in the FIFO is considered as a starting point of reception and from that point onwards required length of the data and terminal will be expected to retrieve.

Additional package terminator — Indicates end of data

'E' (default) | string | char | number from 0 to 255

The data located at the end of the received data package, which is not part of the data being received, and indicates the end of data. The additional package terminator must be represented using ASCII characters. Use a string or a number (0–255). You must add single quotes around strings entered for this parameter, but the quotes are not received or included in the total byte count. To specify a null value (no package terminator), enter two single quotes only.

The data type of terminator is not related to the data type mentioned on the block.

Number of retries for header receive check — Custom retrial count for header receive check

16 (default) | positive integer, finite | scalar

This parameter ensures to check the expected header as part of receive data.

When the data is received in the FIFO, the block verifies for the header in the received data one by one. If the data does not match with the header, the block will discard the data and continue looking for the header in the next data until the retry count expires.

If the header matches within the retry count, then it is considered as start of the packet and the further received data is considered as valid data.

Data type — Data type of output data

uint8 (default) | single | int8 | int16 | uint16 | int32 | uint32

The data type of the output data.

If data is transmitted as uint8 but SCI receive block output is expected to be int16/int32 then it is assumed that even number of bytes are present and that the output is formatted in different data type. In case if there are odd number of data bytes are present then last byte will be missed in the formatting even if the status is showing No Error.

Data length option — Data length the block receives

Length via dialog (default) | Length via input port | Variable length

Select the data length option for the block.

• Length via dialog - Length of the data to be received is provided via Data length parameter.

• Length via input port - the block receives variable size data depending on the length received at the input port. If the length received at the input port is greater than the length provided in the maximum data length parameter, then maximum data length is considered.

• Variable length - The data is received until the tail matches in non-blocking mode. Ensure that the tail is not present as a part of data. When only header and terminator is available and data is not available then the status is set to No Error with variable data length set to zero.

  • If terminator value does not match till maximum length or if the data is not available in between then the block will output the received data along with its length and status will be set to Partial data available.

  • If terminator value is not provided the block tries to receive data of max data length. If length of the data read is less than max length or if the data is not available in between then the block will output received data with its length and status will be set to Partial data available.

  • If data is not read then status is set to Data not available.

  • The status is read as data not available when Header and terminator received with no data.

  • Tail to be avoided as part of SCI Data when using in variable length as presence of Tail is treated as end of Data Packet.

  • Output data port length is 0 if no data is received in variable length mode.

To enable input port length, select data length option as Length via input port.

Data length — Number of data types the block receives

1 (default) | positive integer, finite | scalar

The number of Data type the block receives (not bytes). If this parameter is set to more than 1, the output will be a vector. Ensure that the data length specified is same as that of the SCI Transmit block from which data is received.

Dependencies

To enable this parameter, set the Data length option parameter to Length via dialog.

Max data length — Maximum number of data types the block receives

1 (default) | positive integer, finite | positive integer, finite

The maximum number of Data type the block can receive (not bytes).

If the data size to be received (based on data length or max data length, header, terminator and data type) is greater than FIFO size bytes then it will result in loss of data.

Dependencies

To enable this parameter, set the Data length option parameter to either Length via input port or Variable length.

Initial output — Default value output from block

0 (default) | scalar | vector

The default value output from the SCI Receive block. This value is output, for example,when the Action taken when connection timeout parameter is set to Output the last received value and a connection time-out occurs before data is received.

Dependencies

To enable this parameter, set the Data length option parameter to either Length via input port or Length via dialog.

Action taken when connection times out — Select type of output when connection times out

Output the last received value (default) | Output custom value

Specifies what to output when a connection time out occurs. If Output the last received value is selected, the block outputs the last received value. If a value has not been received, the block outputs the Initial output value.

If you select Output custom value, use the Output value when connection times out parameter to set the custom value.

Dependencies

To enable this parameter, set the Data length option parameter to either Length via input port or Length via dialog.

Output value when connection times out — Custom output value from block when connection times out

0 (default) | scalar | vector

Set the custom time out value.

Output value when connection times out parameter is available only when Action taken when connection times out parameter is set to Output custom value.

Dependencies

To enable this parameter, set the Data length option parameter to either Length via input port or Length via dialog.

Sample time — Frequency at which data is read from SCI device

0.1 (default) | -1 | scalar

Sample time for the block in seconds. To execute this block asynchronously, set this parameter to -1.

Dependencies

To enable this parameter, set the Data length option parameter to either Length via dialog or Variable length.

The sample time will inherit properties from input port when data length option is set to Length via input port.

Wait until data received — Wait until requested data is available

off (default) | on

• on — If this option is enabled, the system waits until data is available to read (when data length is reached). The read operation runs in the blocking mode. The read operation is blocked when the block is waiting for the requested data. If data is available, the block outputs the data. If data is not available, the block waits for the data.

  A task overrun occurs if the target hardware is still waiting for the data when the next read operation begins.

  To fix overruns, increase the time step by using the Sample time parameter.

• off — If this option is disabled, the system checks FIFO at each time step (in polling mode) for data to read. If data is present, the block reads and outputs the contents. If data is not present, the block outputs the last value and continues. When you clear this parameter, the read operation runs in the nonblocking mode.

Dependencies

To enable this parameter, set the Data length option parameter to either Length via input port or Length via dialog.

Note

When data length option is selected as Variable length, the block execution will always occurs in non-blocking mode.

Timeout — Amount of time in seconds the block waits until data is received

inf (default) | positive value greater than 0

Specify the amount of time that the block should wait during each time step if the data is not available in the receive FIFO to read. If timeout occurs, the read operation is aborted.

If the value is set to inf the block waits infinitely for data to be available in FIFO.

Note

3 types of mode can be achieved with parameters Wait until data received and Timeout.

• Blocking mode - In blocking mode, parameters Wait until data received is enabled and Timeout set to inf.

  In this mode, if data is not available in FIFO to read, it will wait for infinite time until the data is available to read.

• Blocking mode with Timeout - In blocking mode with timeout, parameters Wait until data received is enabled and Timeout set to any finite value > 0.

  In this mode if data is not available in FIFO to read, it will wait checking the FIFO status until the timeout value mentioned. If data is not available in FIFO to read within that time then the SCI Receive block will output status as timeout.

• Non-Blocking mode - In Non-Blocking mode, parameter Wait until data received is disabled.

  In this mode the SCI Receive block will read the data if the data is available in FIFO else the SCI Receive block will output status as Data not available.

• In order to receive data of length more than FIFO length use either blocking mode or blocking mode with timeout. This ensures of extra time to get remaining data in FIFO after reading entire FIFO. You might encounter data loss, if you try to receive data greater than the FIFO length in Non-Blocking mode.

  In blocking mode with and without timeout enabled, you might encounter task overrun as it waits for the data to read.

Dependencies

To enable this parameter, set the Data length option parameter to either Length via input port or Length via dialog and enable the parameter Wait until data received.

Output receiving status — Status of serial communication

off (default) | on

Creates a Status block output that provides the status of serial communication.