FtControlSetReceiver.h

00001 #ifndef FTCONTROLSETRECEIVER_H
00002 #define FTCONTROLSETRECEIVER_H
00003 
00004 #include "FtControlSetMessage.h"
00005 #include "InterruptIn.h"
00006 #include "FunctionPointer.h"
00007 #include "TimeoutTweaked.h"
00008 
00009 using namespace mbed;
00010 
00011 /// Receiver interface for the fischertechnik IR control set
00012 ///
00013 /// 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>
00014 /// The ft IR remote control uses some kind of <A HREF="http://www.sbprojects.com/knowledge/ir/rcmm.php"> RC-MM Protocol </A>.
00015 /// 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.
00016 /// Each message delivers the complete remote control status encoded into 30 bits.
00017 /// The structure of the message can be seen in FtControlSetMessage.h.
00018 /// The protocol uses Pulse Distance Modulation (PDM) with two bits (di-bit) per pulse, hence four different
00019 /// distances. A transmission consists of 16 pulses (15 distances) for a total of 30 bits.
00020 ///
00021 /// I assume that the ft control set works fine with standard 38kHz IR detectors. I have used a CHQ0038 from a broken DVD Player.
00022 /// It can be onnected directly to the mebed: GND, VCC->3.3V and the signal line to any of the numbered mbed gpios.
00023 ///
00024 /// 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
00025 /// 3% and 5%. This driver "ignores" up to 3 consecutive receive errors, i.e. it just indicates an error but still provides
00026 /// the last correctly received message, before it resets the message to zero after the fourth error.
00027 ///
00028 /// Some fluorescent energy saving lamp might disturb the transmision quite heavily.
00029 
00030 
00031 class FtControlSetReceiver
00032 {
00033     InterruptIn m_pulseIRQ;
00034 
00035     uint32_t m_rxBuffer;  /// receive message buffer
00036     uint32_t m_nPulses;   /// receive pulse counter (15 pulses per message)
00037     uint32_t m_timeOfLastEdge; /// signal edge time stamp memory
00038     uint8_t  m_nOnes;     /// number of received high bits for parity calculation
00039 
00040     volatile uint32_t m_errorCount;    /// counter of observed receive errors
00041     uint8_t  m_nGracefullyIgnoredErrors;  /// error counter that reset on successful message reception
00042 
00043     volatile uint32_t m_lastMessage; /// last message received correctly
00044 
00045     FunctionPointer m_callback; ///callback for user code that is called afetr successful message reception
00046 
00047     TimeoutTweaked m_messageTimeout; /// Timeout for message reset when sender is inactive
00048     TimeoutTweaked m_receiveTimeout; /// receive timeout
00049     TimeoutTweaked m_recoverTimeout; /// error recovery timeout
00050 
00051     static const uint32_t c_pulseWidthLimits[5]; /// di-bit discrimination times
00052     static const uint32_t c_pulseWidthDelta = 100;//101;  /// di-bit discrimination pulse width delta
00053     static const uint32_t c_pulseWidthOffset = 795;//793; /// di-bit common pulse width base
00054     static const uint32_t c_maxPulseTime = c_pulseWidthOffset+7*c_pulseWidthDelta/2;  /// reveive timeout
00055     static const uint32_t c_messageTimeout[2]; /// message timeout depends on selected sender frequency
00056     static const uint8_t  c_errorsToBeGracefullyIgnored = 3; /// number of consecutive errors after which the message is reset
00057     static const uint32_t c_recoverTimeout = c_maxPulseTime; /// receiver is deactivated for this time after a receive error (IRQ burst suppression)
00058 
00059     void pulseISR(); /// pulse handler
00060     void messageTimeoutISR(); /// message time out handler
00061     void recoverISR();  /// reactivates the pulse handler after recover timeout
00062 
00063     void handleReceiveError();
00064 
00065 public:
00066 
00067     /// Create a receiver
00068     /// @parameter in: The pin the IR detector's message line is connected to
00069     FtControlSetReceiver(PinName in);
00070 
00071     /// get the last received message
00072     FtControlSetMessage getMessage()const {
00073         return FtControlSetMessage(m_lastMessage);
00074     };
00075 
00076     /// get number of receive errors
00077     uint32_t getErrorCount()const {
00078         return m_errorCount;
00079     }
00080 
00081     /// hook a call back into the receiver ISR e.g. for sending a RTOS message.
00082     /// called on each update or receive error
00083     void setCallback(const FunctionPointer& callback) {
00084         m_callback=callback;
00085     };
00086 };
00087 
00088 
00089 #endif
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