Chris Taylor / SignalCapture

Provides a simple way to capture the wave form of a pin. For example it can be used to capture the digital state transitions of a pin connected to an IR receiver. These signals can later be played back using the Signal Generator library to control IR devices. The library supports two means of capturing the signal. The signal can be captured on any digital pin using polling while for higher resolution and more accurate timing the interrupt driven capture feature can be used.

DigitalPinCapture.h

Committer:
taylorza
Date:
2014-09-27
Revision:
0:c6f86d422a7e

File content as of revision 0:c6f86d422a7e:

///////////////////////////////////////////////////////////////////////////////
// Signal Capture Library
// Author: Chris Taylor (taylorza)
#ifndef __DIGITALPINCAPTURE_H__
#define __DIGITALPINCAPTURE_H__

/** Captures the digital wave form of a pin into a timing buffer. */
class DigitalPinCapture
{
    public:
        /** Create an instance of DigitalPinCapture connected to the specified pin 
         * @note The DigitalPinCapture class polls the state of the pin and therefore might be less accurate than
         * using InterruptPinCapture. However, it has the advantage that it does not require an interrupt capable pin.
        */
        DigitalPinCapture(PinName pin, PinMode mode);
        
        /** Maximum time to wait for waveform data to arrive or completely fill the timing buffer. 
         * @param us Timeout specified in microseconds
         */
        void setReadTimeout(uint32_t us);
        
        /** Waits for the pin to transition to the trigger state and proceeds to capture the
         * pins transition timing into the timing buffer.
         * @param triggerState State that the pin must transistion to before the readings are captured
         * @param pReadings Pointer to the timing buffer that will contain the readings in microseconds
         * @param count The maximum number of readings that can be held in the buffer
         * @returns The number of timings captured in the buffer.
         */      
        int read(bool triggerState, uint32_t *pReadings, int count);
        
        /** Immediately start capturing the pin transition timing into the timing buffer.
         * @param pInitialState Pointer to a bool that will have the initial state of the pin at the time the capture started.
         * @param pReadings Pointer to the timing buffer that will contain the readings in microseconds
         * @param count The maximum number of readings that can be held in the buffer
         * @returns The number of timings captured in the buffer.
         */      
        int read(bool *pInitialState, uint32_t *pReadings, int count);
        
    private:
        int readInternal(bool *pPinState, uint32_t *pReadings, int count, bool waitForTrigger);
        
    private:        
        DigitalIn _signalPin;            
        uint32_t _readTimeout;        
};
#endif //__DIGITALPINCAPTURE_H__