Tutorial

General usage

To use the library for decoding RC protocols in your Arduino project, follow these steps:

  1. Include Necessary Libraries:

#include <SerialIO.h>

  1. Define Channel Data Structure:

crsf_channels_t channelData;

  1. Instantiate SerialIO Object:

SerialIO *receiver = new crsf(&Serial1, pinRX, pinTX);

To instantiate a SerialIO object for receiving data only:

SerialIO *receiver = new crsf(&Serial1, pinRX);

  1. Initialize Communication:

void setup() {
    receiver->begin();
}

  1. Process Incoming Data:

receiver->processIncoming();

  1. Retrieve Channel Data:

receiver->getChannel(&channelData);

Using software serial

If you are using a board that does not have hardware serial ports, you can use the SoftwareSerial library to create a software serial port. The SerialIO class can accept a SoftwareSerial object, but the begin method does not support software serial, so after creating the object, you need to manually initiate the software serial port.

Note

On AVR boards, only ibus, and fport protocols are supported (fport required an external inverter circuit), this is because sbus and crsf use unusual baudrate that are not supported by the hardware serial. sbus can be used, by using a software serial library, but it is not recommended.

Sbus

#include <SoftwareSerial.h>
#include <SerialIO.h>

#define pinRX 2
#define pinTX 3
#define SBUS_BAUDRATE 100000

/** SoftwareSerial(pinRX, pinTX, true);
 *                               ^^^^
 *                               set to true because sbus uses inverted uart
 */

SoftwareSerial *mySerial = new SoftwareSerial(pinRX, pinTX, true);
mySerial.begin(SBUS_BAUDRATE);
SerialIO *receiver = new sbus(mySerial);

Crossfire

Note

Crossfire uses a rather high baudrate of 420000, which is not supported by hardware serial and for software serial, it is not recommended to use it, because the software serial library is not optimized for high baudrate. The following code is not tested. Best alternative would be to use a better microcontroller or if you are using ELRS receivers, then reduce the baudrate to 115200, which is supported by hardware and software serial.

#include <SoftwareSerial.h>
#include <SerialIO.h>

#define pinRX 2
#define pinTX 3
#define CRSF_BAUDRATE 100000

SoftwareSerial *mySerial = new SoftwareSerial(pinRX, pinTX);
mySerial.begin(CRSF_BAUDRATE);
SerialIO *receiver = new crsf(mySerial);

Monitoring Communication

You can monitor the communication status on certain protocols, to ensure reliability of the received channel data.

Serial Communication

You can monitor the serial communication using the getSerialConnectionStatus() method on the receiver instance. This method returns true if the serial communication is running without errors, otherwise it returns false.

#include <SerialIO.h>

rc_channels_t channelData;
sbus receiver(&Serial);

// within your setup routine
receiver.begin();

// within your program loop
receiver.processIncoming();
receiver.getChannel(&channelData);

bool serialConnectionStatus = receiver.getSerialConnectionStatus();

if(!serialConnectionStatus) {
    // handle failsafe of channelData
}

Radio connection

You can monitor the radio connection of the receiver using the getFailsafe() method on the receiver instance. The failsafe indicates when the receiver has lost connection to the transmitter. When the failsafe is activated, the channel data might be set to predefined values or hold the last known values.

You can also monitor the quality of the connection with getFramelost() method on the receiver instance. Usually lost frame indicates when a frame is lost between the transmitter an receiver. Failsafe activation requires that many frames ahs been lost in a row.

Note

Some receivers might not provide any failsafe or frame loss information via SBus protocol. In that case, the methods will always return false.

#include <SerialIO.h>

rc_channels_t channelData;
sbus receiver(&Serial);

// within your setup routine
receiver.begin();

// within your program loop
receiver.processIncoming();
receiver.getChannel(&channelData);

bool failsafe = receiver.getFailsafe();
bool frameLost = receiver.getFramelost();

if(failsafe) {
    // handle failsafe of channelData
}

if(frameLost) {
    // handle frame lost event
}

See Also