Mirror with some correction
Dependencies: mbed FastIO FastPWM USBDevice
Plunger/tsl14xxSensor.h
- Committer:
- mjr
- Date:
- 2019-11-28
- Revision:
- 100:1ff35c07217c
- Parent:
- 87:8d35c74403af
- Child:
- 101:755f44622abc
File content as of revision 100:1ff35c07217c:
// Base class for TSL14xx-based plunger sensors. // // This provides a common base class for plunger sensors based on // AMS/TAOS TSL14xx sensors (TSL1410R, TSL1412S, TSL1401CL). The sensors // in this series all work the same way, differing mostly in the number // of pixels. However, we have two fundamentally different ways of using // these image sensors to detect position: sensing the position of the // shadow cast by the plunger on the sensor, and optically reading a bar // code telling us the location of the sensor along a scale. This class // provides the low-level pixel-sensor interface; subclasses provide the // image analysis that figures the position from the captured image. #ifndef _TSL14XXSENSOR_H_ #define _TSL14XXSENSOR_H_ #include "plunger.h" #include "edgeSensor.h" #include "barCodeSensor.h" #include "TSL14xx.h" class PlungerSensorImageInterfaceTSL14xx: public PlungerSensorImageInterface { public: PlungerSensorImageInterfaceTSL14xx(int nativePix, PinName si, PinName clock, PinName ao) : PlungerSensorImageInterface(nativePix), sensor(nativePix, si, clock, ao) { } // is the sensor ready? virtual bool ready() { return sensor.ready(); } // is a DMA transfer in progress? virtual bool dmaBusy() { return sensor.dmaBusy(); } virtual void init() { sensor.clear(); } // get the average sensor scan time virtual uint32_t getAvgScanTime() { return sensor.getAvgScanTime(); } protected: virtual void getStatusReportPixels( uint8_t* &pix, uint32_t &t, int axcTime, int extraTime) { // The sensor's internal buffering scheme makes it a little tricky // to get the requested timing, and our own double-buffering adds a // little complexity as well. To get the exact timing requested, we // have to work with the buffering pipeline like so: // // 1. Call startCapture(). This waits for any in-progress pixel // transfer from the sensor to finish, then executes a HOLD/SI pulse // on the sensor. The HOLD/SI takes a snapshot of the current live // photo receptors to the sensor shift register. These pixels have // been integrating starting from before we were called; call this // integration period A. So the shift register contains period A. // The HOLD/SI then grounds the photo receptors, clearing their // charge, thus starting a new integration period B. After sending // the HOLD/SI pulse, startCapture() begins a DMA transfer of the // shift register pixels (period A) to one of our two buffers (call // it the EVEN buffer). // // 2. Wait for the current transfer (period A to the EVEN buffer) // to finish. The minimum integration time is the time of one // transfer cycle, so this brings us to the minimum time for // period B. // // 3. Now pause for the requested extra delay time. Period B is // still running at this point (it keeps going until we start a // new capture), so this pause adds the requested extra time to // period B's total integration time. This brings period B to // exactly the requested total time. // // 4. Call startCapture() to end period B, move period B's pixels // to the sensor's shift register, and begin period C. This // switches DMA buffers, so the EVEN buffer (with period A) is now // available, and the ODD buffer becomes the DMA target for the // period B pixels. // // 5. Wait for the period B pixels to become available, via // waitPix(). This waits for the DMA transfer to complete and // hands us the latest (ODD) transfer buffer. // sensor.startCapture(axcTime); // begin transfer of pixels from incoming period A, begin integration period B sensor.wait(); // wait for scan of A to complete, as minimum integration B time wait_us(long(extraTime) * 100); // add extraTime (0.1ms == 100us increments) to integration B time sensor.startCapture(axcTime); // begin transfer of pixels from integration period B, begin period C; period A pixels now available // wait for the DMA transfer of period B to finish, and get the // period B pixels sensor.waitPix(pix, t); } // reset after a status report virtual void resetAfterStatusReport(int axcTime) { // It takes us a while to send all of the pixels, since we have // to break them up into many USB reports. This delay means that // the sensor has been sitting there integrating for much longer // than usual, so the next frame read will be overexposed. To // mitigate this, make sure we don't have a capture running, // then clear the sensor and start a new capture. sensor.wait(); sensor.clear(); sensor.startCapture(axcTime); } // the low-level interface to the TSL14xx sensor TSL14xx sensor; }; // --------------------------------------------------------------------- // // Subclass for the large sensors, such as TSL1410R (1280 pixels) // and TSL1412S (1536 pixels). // // For the large sensors, pixel transfers take a long time: about // 2.5ms on the 1410R and 1412S. This is much longer than our main // loop time, so we don't want to block other work to do a transfer. // Instead, we want to do our transfers asynchronously, so that the // main loop can keep going while a transfer proceeds. This is // possible via our DMA double buffering. // // This scheme gives us three images in our pipeline at any given time: // // - a live image integrating light on the photo receptors on the sensor // - the prior image being held in the sensor's shift register and being // transferred via DMA into one of our buffers // - the image before that in our other buffer // // Integration of a live image starts when we begin the transfer of the // prior image. Integration ends when we start the next transfer after // that. So the total integration time, which is to say the exposure // time, is the time between consecutive transfer starts. It's important // for this time to be consistent from image to image, because that // determines the exposure level. We use polling from the main loop // to initiate new transfers, so the main loop is responsible for // polling frequently during the 2.5ms transfer period. It would be // more consistent if we did this in an interrupt handler instead, // but that would complicate things considerably since our image // analysis is too time-consuming to do in interrupt context. // class PlungerSensorTSL14xxLarge: public PlungerSensorImageInterfaceTSL14xx { public: PlungerSensorTSL14xxLarge(int nativePix, PinName si, PinName clock, PinName ao) : PlungerSensorImageInterfaceTSL14xx(nativePix, si, clock, ao) { } virtual void readPix(uint8_t* &pix, uint32_t &t, int axcTime) { // start reading the next pixel array (this waits for any DMA // transfer in progress to finish, ensuring a stable pixel buffer) sensor.startCapture(axcTime); // get the image array from the last capture sensor.getPix(pix, t); } }; // --------------------------------------------------------------------- // // Subclass for the small sensors, such as TSL1401CL (128 pixels). // // For the small sensors, we can't use the asynchronous transfer // scheme we use for the large sensors, because the transfer times // are so short that the main loop can't poll frequently enough to // maintain consistent exposure times. With the short transfer // times, though, we don't need to do them asynchronously. // // Instead, each time we want to read the sensor, we do the whole // integration and transfer synchronously, so that we can precisly // control the total time. This requires two transfers. First, // we start a transfer in order to set the exact starting time of // an integration period: call it period A. We wait for the // transfer to complete, which fills a buffer with the prior // integration period's pixels. We don't want those pixels, // because they started before we got here and thus we can't // control how long they were integrating. So we discard that // buffer and start a new transfer. This starts period B while // transferring period A's pixels into a DMA buffer. We want // those period A pixels, so we wait for this transfer to finish. // class PlungerSensorTSL14xxSmall: public PlungerSensorImageInterfaceTSL14xx { public: PlungerSensorTSL14xxSmall(int nativePix, PinName si, PinName clock, PinName ao) : PlungerSensorImageInterfaceTSL14xx(nativePix, si, clock, ao) { } // read the image virtual void readPix(uint8_t* &pix, uint32_t &t, int axcTime) { // Clear the sensor. This sends a HOLD/SI pulse to the sensor, // which ends the current integration period, starts a new one // (call the new one period A) right now, and clocks out all // of the pixels from the old cycle. We want to discard these // pixels because they've been integrating from some time in // the past, so we can't control the exact timing of that cycle. // Clearing the sensor clocks the pixels out without waiting to // read them on DMA, so it's much faster than a regular transfer // and thus gives us the shortest possible base integration time // for period A. sensor.clear(); // Start a real transfer. This ends integration period A (the // one we just started), starts a new integration period B, and // begins transferring period A's pixels to memory via DMA. We // use the auto-exposure time to get the optimal exposure. sensor.startCapture(axcTime); // wait for the period A pixel transfer to finish, and grab // its pixels sensor.waitPix(pix, t); } }; // ------------------------------------------------------------------------- // // Concrete TSL14xx sensor types // // TSL1410R sensor - edge detection sensor class PlungerSensorTSL1410R: public PlungerSensorEdgePos { public: PlungerSensorTSL1410R(PinName si, PinName clock, PinName ao) : PlungerSensorEdgePos(sensor, 1280), sensor(1280, si, clock, ao) { } protected: PlungerSensorTSL14xxLarge sensor; }; // TSL1412R - edge detection sensor class PlungerSensorTSL1412R: public PlungerSensorEdgePos { public: PlungerSensorTSL1412R(PinName si, PinName clock, PinName ao) : PlungerSensorEdgePos(sensor, 1536), sensor(1536, si, clock, ao) { } protected: PlungerSensorTSL14xxLarge sensor; }; // TSL1401CL - bar code sensor class PlungerSensorTSL1401CL: public PlungerSensorBarCode<7, 0, 1, 16> { public: PlungerSensorTSL1401CL(PinName si, PinName clock, PinName ao) : PlungerSensorBarCode(sensor, 128), sensor(128, si, clock, ao) { } protected: PlungerSensorTSL14xxSmall sensor; }; #endif