Improve HM01B0 PIO sync

Have to disable DMA to reset write address
Also, restarting PIO SM doesn't clear RX buffer, have to read out manually
Still not perfect. Start of frame seems consistently good, but DMA seems to loose sync or something part way through with a lot of frames

Author: sfe-SparkFro

drivers/camera/hm01b0_pio.py

@@ -200,7 +200,6 @@ def __init__(
         self.sm_id = sm_id
         self.i2c_address = i2c_address
         self.buffer = np.zeros((244, 324), dtype=np.uint8)
-        # self.buffer = bytearray(244 * 324)
 
         Pin(pin_d0, Pin.IN)
         Pin(pin_vsync, Pin.IN)
@@ -286,7 +285,6 @@ def start_pio_dma(self):
         )
         self.dma.config(
             read = self.sm,
-            write = self.buffer,
             count = 244 * 324,
             ctrl = dma_ctrl
         )
@@ -297,10 +295,18 @@ def start_pio_dma(self):
         )
 
     def _vsync_handler(self):
-        self.sm.restart()
+        # Disable DMA before reconfiguring it
+        self.dma.active(False)
+
+        # Ensure PIO RX FIFO is empty
+        while self.sm.rx_fifo() > 0:
+            self.sm.get()
+        
+        # Reset the DMA write address
         self.dma.write = self.buffer
+
+        # Start the DMA
         self.dma.active(True)
-        # print("new frame:", time.ticks_ms())
 
     @rp2.asm_pio(
             in_shiftdir = rp2.PIO.SHIFT_LEFT,