Helmut Schmücker / FtControlSet

Receiver interface for the fischertechnik IR control set

Dependencies:   NeedfulThings

Receiver interface for the fischertechnik IR control set.

An mbed port of the code found on this ft community WIKI page The ft IR remote control uses some kind of RC-MM Protocol . When any of the controls is applied the remote control sends updates at a rate of at 1/120ms or 1/90ms depending on the senders frequency setting. Each message delivers the complete remote control status encoded into 30 bits. The structure of the message can be seen in FtControlSetMessage.h.

I assume that the ft control set works fine with standard 38kHz IR detectors. I have used a CHQ0038 from a broken DVD Player. It can be connected directly to the mbed: GND, VCC->3.3V and the signal line to any of the numbered mbed gpios.

The PDM timing of the ft IR control set isn't that exact. Thus receive errors occur quite frequently. I am observing an error rate somewhere between 3% and 5%. This driver "ignores" up to 3 consecutive receive errors, i.e. it just indicates an error but still provides the last correctly received message, before it resets the message to zero after the fourth error.

FtControlSetReceiver.h

Committer:
humlet
Date:
2013-03-18
Revision:
2:1ae8bb468515
Parent:
1:3904ef8c606e
Child:
3:038f86bac6cc

File content as of revision 2:1ae8bb468515:

#ifndef FTCONTROLSETRECEIVER_H
#define FTCONTROLSETRECEIVER_H

#include "FtControlSetMessage.h"
#include "InterruptIn.h"
#include "FunctionPointer.h"
#include "Timeout.h"

using namespace mbed;

/// Receiver interface for the fischertechnik IR control set
///
/// An mbed port of the code found on this <A HREF="http://www.ftcommunity.de/wiki.php?action=show&topic_id=36">ft community WIKI page</a>
/// The ft IR remote control uses some kind of <A HREF="http://www.sbprojects.com/knowledge/ir/rcmm.php"> RC-MM Protocol </A>.
/// When any of the controls is applied the remote control sends updates at a rate of 1/90ms~12Hz.
/// Each message delivers the complete remote control status encoded into 30 bits.
/// The structure of the message is can be seen in FtControlSetMessage.h.
/// The protocol uses Pulse Distance Modulation (PDM) with two bits (dibit) per pulse, hence four different
/// distances. A transmission consists of 16 pulses (15 distances) for a total of 30 bits.
///
/// I assume that the ft control set works fine with standard 38kHz IR detectors. I have used a CHQ0038 from a broken DVD Player.
/// It can be onnected directly to the mebed: GND, VCC->3.3V and the signal line to any of the numbered mbed gpios.
class FtControlSetReceiver
{
    InterruptIn m_pulseIRQ;

    uint32_t m_rxBuffer;
    uint32_t m_nPulses;
    uint32_t m_timeOfLastEdge;
    uint8_t  m_nOnes;
    
    uint32_t m_errorCount;
    uint8_t  m_nGracefullyIgnoredErrors;  

    FtControlSetMessage m_lastMessage;

    FunctionPointer m_callBack;

    Timeout m_messageTimeout;
    Timeout m_receiveTimeout;
    
    //static const uint32_t c_pulseLengthLimits[5];
    static const uint32_t c_pulseLengthDelta = 100;//101;
    static const uint32_t c_pulseLengthOffset = 795;//793;
    static const uint32_t c_maxPulseTime = c_pulseLengthOffset+7*c_pulseLengthDelta/2;
    static const uint32_t c_messageTimeout[2];
    static const uint8_t c_errorsToBeGracefullyIgnored = 3;
    
    void pulseISR();
    void messageTimeoutISR();
    void recoverISR();

    void messageReceived(FtControlSetMessage::Status status);
    void handleReceiveError();
    
public:
    
    uint32_t msgCnt;
    
    /// Create a receiver
    /// @parameter in: The pin the IR detector's message line is connected to
    FtControlSetReceiver(PinName in);

    /// get the last received message
    FtControlSetMessage getLastMessage()const {
        return m_lastMessage;
    };

    /// get number of receive errors
    uint32_t getErrorCount()const {
        return m_errorCount;
    }

    /// hook a call back into the receiver ISR e.g. for sending a RTOS message.
    /// called on each update or receive error
    void setCallBack(const FunctionPointer& callBack) {
        m_callBack=callBack;
    };
};


#endif