Add dma_ws2812.py

dma_ws2812.py

@@ -0,0 +1,87 @@
+# Example based on pio_ws2812.py, but modified to use
+# a DMA channel to push out the data to the PIO
+
+import array, time
+from machine import Pin
+import rp2
+
+# Configure the number of WS2812 LEDs.
+NUM_LEDS = 9
+
+SM = 0
+
+PIO0_BASE = 0x50200000
+PIO1_BASE = 0x50300000
+PIO0_BASE_TXF0 = PIO0_BASE+0x10
+PIO0_BASE_TXF1 = PIO0_BASE+0x14
+PIO0_BASE_TXF2 = PIO0_BASE+0x18
+PIO0_BASE_TXF3 = PIO0_BASE+0x1c
+
+PIO1_BASE_TXF0 = PIO1_BASE+0x10
+PIO1_BASE_TXF1 = PIO1_BASE+0x14
+PIO1_BASE_TXF2 = PIO1_BASE+0x18
+PIO1_BASE_TXF3 = PIO1_BASE+0x1c
+
+
+if SM < 4:
+    TFX = PIO0_BASE+0x10 + SM * 4
+else:
+    TFX = PIO1_BASE+0x10 + (SM-4) * 4
+    
+
+
+@rp2.asm_pio(
+    sideset_init=rp2.PIO.OUT_LOW,
+    out_shiftdir=rp2.PIO.SHIFT_LEFT,
+    autopull=True,
+    pull_thresh=24,
+)
+def ws2812():
+    # fmt: off
+    T1 = 2
+    T2 = 5
+    T3 = 3
+    wrap_target()
+    label("bitloop")
+    out(x, 1)               .side(0)    [T3 - 1]
+    jmp(not_x, "do_zero")   .side(1)    [T1 - 1]
+    jmp("bitloop")          .side(1)    [T2 - 1]
+    label("do_zero")
+    nop()                   .side(0)    [T2 - 1]
+    wrap()
+    # fmt: on
+
+
+# Create the StateMachine with the ws2812 program, outputting on Pin(2).
+sm = rp2.StateMachine(SM, ws2812, freq=8_000_000, sideset_base=Pin(0))
+
+# Start the StateMachine, it will wait for data on its FIFO.
+sm.active(1)
+
+# Dummy data
+ar = array.array("I", [0 for _ in range(NUM_LEDS)])
+r = 0xff
+g = 0xff
+b = 0xff
+ar[0] = 0xff000000
+ar[1] = 0x00ff0000
+ar[2] = 0x0000ff00
+ar[3] = r<<24 + g<<16 + b<<8
+
+
+# starts the transfer, using DMA channel 0
+def dma_out():
+    import dma, uctypes
+    dma.init_channels()
+    d0=dma.CHANNELS[0]
+    d0.CTRL_TRIG.EN = 0
+    d0.TRANS_COUNT = NUM_LEDS
+    d0.READ_ADDR = uctypes.addressof(ar)
+    d0.WRITE_ADDR = TFX
+    d0.CTRL_TRIG.INCR_WRITE = 0
+    d0.CTRL_TRIG.INCR_READ = 1
+    d0.CTRL_TRIG.DATA_SIZE = 2
+    d0.CTRL_TRIG.EN = 1
+    
+dma_out()
+time.sleep(1)