Multiwii Read RC

Reads RC values from the auto-pilot.

Library

Description

The Multiwii Read RC block uses the Multiwii protocol on the input stream to send a command to the aircraft to read the RC values from the auto-pilot. The Multiwii Read RC block sends a MSP_RC message to the auto-pilot.

This block is designed to be used with blocking I/O. It is typically used with a stream connected to a serial port. To open the stream a Multiwii Connect block should be used.

The output of the block is a vector of RC values. The units depend on the Output units parameter. The order of the RC channels in the vector depends on the auto-pilot but the first eight channels are typically roll, pitch, throttle, yaw, auxiliary 1, auxiliary 2, auxiliary 3 and auxiliary 4, in that order.

A copy of the stream is also output so that the Multiwii blocks may be chained together.

If an error occurs, then the block returns a negative error code at its err output. The Compare to Error block may be used to check for specific error codes. If the stream is not valid because it is not yet connected, the err output will be zero since this condition is expected and the validity of the stream may be checked using the con output of the Multiwii Connect block.

Helpful Hints

Other uses of this block

Although it is intended for use in the main diagram with the other Multiwii blocks, the Multiwii Read RC block may be used with the Advanced stream blocks, even in an asynchronous thread.

Input Ports

stm

A reference to the stream created by the Multiwii Connect block. If a connection has not yet been established, then the err output of the Multiwii Read RC block will be zero.

Output Ports

stm

A reference to the stream. This output is merely a copy of the stm input. Providing this output makes it much easier to establish the execution order of Multiwii blocks in the diagram because Simulink generally executes daisy-chained blocks in sequence.

rc

This output depends on the Output units parameter. Each element of the output vector corresponds to a separate RC channel. However the data type and range changes depending on the output units. Refer to the Output units parameter for details.

err

An int32 value indicating whether the data was read successfully. This value will be positive if data was read successfully. It will be zero if data could not be read immediately. If an error occurs then this value is a negative error code. See Error Codes for the different error codes and their values. Use the Compare to Error block rather than the error code itself to check for specific error codes. To check for errors in general use the Compare to Zero block to check whether the err output is less than zero.

Parameters and Dialog Box

Output units

This parameter determines the data type and units of the rc output. The table below shows the output for each of the different units:

Targets

See Also

• Multiwii Connect block
• Multiwii Communications

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