RC Receive

Reads radio control channel data

Since R2025b

Add-On Required: This feature requires the UAV Toolbox Support Package for ArduPilot^® Autopilots add-on.

• 

Libraries:
UAV Toolbox Support Package for ArduPilot Autopilots / Peripheral Blocks

Description

The RC Receive block acquires raw input data from selected channels of an RC transmitter. The block provides options to apply trim and deadzone adjustments for output normalization. Additionally, the block can output auxiliary information such as flight mode, radio signal strength indicator (RSSI), arming status, and motor emergency stop status.

Examples

Verify RC Transmitter Input with RC Receive Block

Test your RC transmitter with the RC Receive block in Simulink.

Limitations

This block is not supported in triggered subsystems.

Ports

Output

Failsafe — Failsafe status

scalar

The RC Receive block outputs the failsafe status by default. If the RC transmitter turns off or loses signal during operation, the failsafe output switches to 1. Use this output to trigger safety mechanisms in your model.

Data Types: double

Ch x Raw — Raw data from the specified RC channel

vector

Raw data for each selected channel. When you enable normalization, it adjusts the output values using the specified trim and deadzone settings.

Data Types: double

Mode — Current flight mode

scalar

The block outputs the flight mode index (starting from 0) based on your Mission Planner configuration. This value indicates the current mapped flight mode.

Dependencies

To enable this port, select the Output flight mode parameter.

Data Types: uint8

RSSI — Radio signal strength

scalar

The block outputs the radio signal strength from the RC transmitter. Use this value in your model for monitoring or implementing safety mechanisms.

Dependencies

To enable this port, select the Output radio signal strength indicator(RSSI) parameter.

Data Types: int32

Arm — Status of vehicle arming

scalar

The block outputs 1 when armed, 0 when disarmed.

Dependencies

To enable this port, select the Output arming status parameter.

Data Types: uint8

Estop — Emergency stop status

scalar

The block outputs a signal that indicates whether the motor emergency stop has been triggered.

Dependencies

To enable this port, select the Output motor emergency stop status parameter.

Data Types: uint8

Parameters

Channels tab

Channel Selection — Channels for raw data

channels

Select which RC channels you want to read from your transmitter. Add or remove channels using the interface. The block displays Ch x Raw outputs based on your selections in this parameter list. You can add a maximum of 16 channels.

Normalize output for channels using trim and deadzone — Apply trim and deadzone to raw RC data

off (default) | on

Select this parameter to normalize the outputs for the selected channels using the specified trim and deadzone settings.

Sample time — Interval at which the block reads values

-1 (default)

The time interval at which the block retrieves values from the ArduPilot autopilot.

Advanced tab

Output flight mode — Enable output port for flight mode

off (default) | on

Select this parameter to enable the Port output port . To view information on the mapping of flight modes to channel values, see Flight Mode Mapping.

Output radio signal strenght indicator(RSSI) — Enable output port for RSSI

off (default) | on

Select this parameter to enable the RSSI output port .

Output arming status — Enable output port for arming status

off (default) | on

Select this parameter to enable the Arm output port .

Output motor emergency stop status — Enable output port for motor emergency stop status

off (default) | on

Select this parameter to enable the Estop output port.

More About

Flight Mode Mapping

ArduPilot supports a wide range of flight modes, each designed to provide specific control characteristics and automation features for different flight scenarios. The following tables outline the mapping between flight mode values and their corresponding meanings for both Plane and Copter firmware.

Flight Mode Mapping for Plane

The table below lists the available flight modes for ArduPilot Plane, along with their associated numeric values and descriptions:

Mapping Table - Plane

Value	Meaning
0	Manual
1	CIRCLE
2	STABILIZE
3	TRAINING
4	ACRO
5	FBWA
6	FBWB
7	CRUISE
8	AUTOTUNE
10	Auto
11	RTL
12	Loiter
13	TAKEOFF
14	AVOID_ADSB
15	Guided
17	QSTABILIZE
18	QHOVER
19	QLOITER
20	QLAND
21	QRTL
22	QAUTOTUNE
23	QACRO
24	THERMAL
25	Loiter to QLand

Flight Mode Mapping for Copter

The following table shows the flight mode mapping for ArduPilot Copter, indicating each mode’s numeric value and its meaning.

Mapping Table - Copter

Value	Meaning
0	Stabilize
1	Acro
2	AltHold
3	Auto
4	Guided
5	Loiter
6	RTL
7	Circle
9	Land
11	Drift
13	Sport
14	Flip
15	AutoTune
16	PosHold
17	Brake
18	Throw
19	Avoid_ADSB
20	Guided_NoGPS
21	Smart_RTL
22	FlowHold
23	Follow
24	ZigZag
25	SystemID
26	Heli_Autorotate
27	Auto RTL
28	Turtle

How Trim and Deadzone Output is Calculated in the RC Receive Block

When you select Using trim & deadzone as the output for a channel in the RC Receive block, the output is normalized based on the RC channel's trim and deadzone settings.

Key Parameters

Here are the parameters used in the normalization calculation:

Key Parameters

Parameter	Description
radio_in	The raw input value from the RC transmitter for the channel.
radio_trim	The trim (center) value of the RC channel. Set via the parameter RCx_TRIM (where x = 1 to 16).
dead_zone	The deadzone value, set via parameter RCx_DZ (e.g., RC1_DZ), which defines the range around the trim where small movements are ignored.
radio_min	The minimum value for the RC channel.
radio_max	The maximum value for the RC channel.
reversed	Boolean indicating if the channel is reversed. If the channel is reversed, this is true.
reverse_mul	Multiplier, set to -1 if reversed, otherwise 1.

Step-by-Step Calculation

The calculation proceeds as follows:

1. Define Deadzone Boundaries:

   dz_min = radio_trim - dead_zone
   dz_max = radio_trim + dead_zone

   • Any input between dz_min and dz_max is considered "neutral" (output = 0).

2. Determine Output Based on Input:

   • Below Deadzone: If radio_in < dz_min and dz_min > radio_min

     output = reverse_mul * (radio_in - dz_min) / (dz_min - radio_min)

   • Above Deadzone: If radio_in > dz_max and radio_max > dz_max

     output = reverse_mul * (radio_in - dz_max) / (radio_max - dz_max)

   • Within Deadzone:

     output = 0

3. Reverse Direction (if applicable):

   • If the channel is reversed, reverse_mul = -1, otherwise reverse_mul = 1.

4. Constrain Output:

   • The output is constrained to the range [-1.0, 1.0]:

     output = constrain_float(output, -1.0, 1.0)

     If the value is more 1, then it is 1 and if the output is less than -1, it is -1.

What Happens When Not Normalized?

When Normalize output for channels using trim and deadzone option is not selected then the RC channel values are not adjusted for trim or deadzone and the formula is calculated using this formula:

trimDzChannelData = static_cast<int16_T>(minChVal + (normTrimDz + 1) * (maxChVal - minChVal) / 2);

This formula is used to convert the normalized RC channel value (which ranges from -1 to 1) back to the actual channel value range defined by the hardware (from minChVal to maxChVal).

• normTrimDz: This is the normalized value (from -1 to 1) obtained from the previous calculation (see the earlier code block).

• minChVal and maxChVal: These are the minimum and maximum possible values for the channel (for example, 1000 and 2000 for many RC systems).

This converts a normalized value (from -1 to 1) back to the original PWM range.

• When normTrimDz = -1, the output is minChVal.

• When normTrimDz = 1, the output is maxChVal.

• Values in between are linearly interpolated.

Version History

Introduced in R2025b