ST7735 driver fix for screen hanging. (#186)

* Fix for the microbit-app hanging issue
* renamed displayIsFree to inProgressLock. Removed inProgress since it is no longer neccessary on account of inProgressLock, removed temporary comments that commented out code.

Author: KierPalin

inc/drivers/ST7735.h

@@ -29,6 +29,7 @@ DEALINGS IN THE SOFTWARE.
 #include "SPI.h"
 #include "Event.h"
 #include "ScreenIO.h"
+#include "CodalFiber.h"
 
 namespace codal
 {
@@ -52,6 +53,7 @@ class ST7735 : public CodalComponent
     uint8_t cmdBuf[20];
     ST7735WorkBuffer *work;
     bool inSleepMode;
+    FiberLock inProgressLock;
 
     // if true, every pixel will be plotted as 4 pixels and 16 bit color mode
     // will be used; this is for ILI9341 which usually has 320x240 screens
@@ -65,12 +67,12 @@ class ST7735 : public CodalComponent
 
     void sendCmd(uint8_t *buf, int len);
     void sendCmdSeq(const uint8_t *buf);
-    void sendDone(Event);
     void sendWords(unsigned numBytes);
     void startTransfer(unsigned size);
     void sendBytes(unsigned num);
     void startRAMWR(int cmd = 0);
 
+    static void sendDone(ST7735* st);
     static void sendColorsStep(ST7735 *st);
 
 public:

source/drivers/ST7735.cpp

@@ -65,7 +65,8 @@
 namespace codal
 {
 
-ST7735::ST7735(ScreenIO &io, Pin &cs, Pin &dc) : io(io), cs(&cs), dc(&dc), work(NULL)
+ST7735::ST7735(ScreenIO &io, Pin &cs, Pin &dc)
+    : io(io), cs(&cs), dc(&dc), work(NULL), inProgressLock(1)
 {
     double16 = false;
     inSleepMode = false;
@@ -145,7 +146,6 @@ struct ST7735WorkBuffer
     unsigned x;
     uint32_t *paletteTable;
     unsigned srcLeft;
-    bool inProgress;
     uint32_t expPalette[256];
 };
 
@@ -269,7 +269,7 @@ void ST7735::sendColorsStep(ST7735 *st)
         if (work->srcLeft == 0)
         {
             st->endCS();
-            Event(DEVICE_ID_DISPLAY, 100);
+            st->sendDone(st);
         }
         else
         {
@@ -301,19 +301,16 @@ void ST7735::startRAMWR(int cmd)
     beginCS();
 }
 
-void ST7735::sendDone(Event)
+void ST7735::sendDone(ST7735 *st)
 {
-    // this executes outside of interrupt context, so we don't get a race
-    // with waitForSendDone
-    work->inProgress = false;
-    Event(DEVICE_ID_DISPLAY, 101);
+    st->inProgressLock.notify();
 }
 
-void ST7735::waitForSendDone()
-{
-    if (work && work->inProgress)
-        fiber_wait_for_event(DEVICE_ID_DISPLAY, 101);
-}
+
+/**
+* Deprecated; no longer neccessary. sendIndexedImage handles this.
+*/
+void ST7735::waitForSendDone() {}
 
 int ST7735::setSleep(bool sleepMode)
 {
@@ -355,15 +352,14 @@ int ST7735::sendIndexedImage(const uint8_t *src, unsigned width, unsigned height
         else
             for (int i = 0; i < 256; ++i)
                 work->expPalette[i] = 0x1011 * (i & 0xf) | (0x110100 * (i >> 4));
-        EventModel::defaultEventBus->listen(DEVICE_ID_DISPLAY, 100, this, &ST7735::sendDone);
     }
 
-    if (work->inProgress || inSleepMode)
+    inProgressLock.wait();
+    if (inSleepMode)
         return DEVICE_BUSY;
 
     work->paletteTable = palette;
 
-    work->inProgress = true;
     work->srcPtr = src;
     work->width = width;
     work->height = height;