Add an extra pixel buffer, implement Write (translating the internal …

…buffer into the to-be-PWMed format).

With this commit, WS281x pixels work as expected.

pixarray/ws281x.go

@@ -13,15 +13,18 @@ type WS281x struct {
  r int
  b int
  w int
+ pixels []byte
  mbox *os.File
  mboxSize uint32
  rp *RasPiHW
  pixHandle uintptr
  pixBusAddr uintptr
  pixBuf mmap.MMap
+ pixBufUint []uint32
  pixBufOffs uintptr
- dmaCb *dmaCallback
+ dmaCb *dmaControl
  dmaBuf mmap.MMap
+ dmaBufOffs uintptr
  dma *dmaT
  pwmBuf mmap.MMap
  pwm *pwmT
@@ -44,6 +47,7 @@ func NewWS281x(numPixels int, numColors int, order int, freq uint, dma int, pins
  r: offsets[1],
  b: offsets[2],
  w: offsets[3],
+ pixels: make([]byte, numPixels*numColors),
  rp: rp,
  }
  wa.mbox, err = wa.mboxOpen()
@@ -69,7 +73,8 @@ func NewWS281x(numPixels int, numColors int, order int, freq uint, dma int, pins
  return nil, fmt.Errorf("couldn't map pixBuf: %v", err)
  }
  fmt.Printf("got offset %d\n", wa.pixBufOffs)
- wa.initDmaCb()
+ wa.pixBufUint = mmapToUintSlice(wa.pixBuf)
+ wa.initDmaControl()
  err = wa.mapDmaRegisters(dma)
  if err != nil {
  wa.unlockMem(wa.pixHandle) // Ignore error
@@ -92,19 +97,62 @@ func (ws *WS281x) MaxPerChannel() int {
 }
 
 func (ws *WS281x) GetPixel(i int) Pixel {
- return Pixel{}
+ p := Pixel{int(ws.pixels[i*ws.numColors+ws.r]), int(ws.pixels[i*ws.numColors+ws.g]), int(ws.pixels[i*ws.numColors+ws.b]), -1}
+ if ws.numColors == 4 {
+ p.W = int(ws.pixels[i*ws.numColors+ws.w])
+ }
+ return p
 }
 
 func (ws *WS281x) SetPixel(i int, p Pixel) {
- ws.pixBuf[int(ws.pixBufOffs)+i*ws.numColors+ws.r] = byte(p.R)
- ws.pixBuf[int(ws.pixBufOffs)+i*ws.numColors+ws.g] = byte(p.G)
- ws.pixBuf[int(ws.pixBufOffs)+i*ws.numColors+ws.b] = byte(p.B)
+ ws.pixels[i*ws.numColors+ws.r] = byte(p.R)
+ ws.pixels[i*ws.numColors+ws.g] = byte(p.G)
+ ws.pixels[i*ws.numColors+ws.b] = byte(p.B)
  if ws.numColors == 4 {
- ws.pixBuf[int(ws.pixBufOffs)+i*ws.numColors+ws.w] = byte(p.W)
+ ws.pixels[i*ws.numColors+ws.w] = byte(p.W)
  }
 }
 
-func (wa *WS281x) Write() error {
- // TODO
+const (
+ SYMBOL_HIGH = 0x6 // 1 1 0
+ SYMBOL_LOW = 0x4 // 1 0 0
+)
+
+func (ws *WS281x) Write() error {
+ pbOffs := (uintptr(ws.dmaCb.sourceAd) - ws.pixBusAddr) / 4
+
+ // We need to wait for DMA to be done before we start touching the buffer it's outputting
+ err := ws.waitForDMAEnd()
+ if err != nil {
+ return fmt.Errorf("pre-DMA wait failed: %v", err)
+ }
+
+ // TODO: channels, do properly - this just assumes both channels show the same thing
+ for c := 0; c < 2; c++ {
+ rpPos := pbOffs + uintptr(c)
+ bitPos := 31
+ for i := 0; i < ws.numPixels; i++ {
+ for j := 0; j < ws.numColors; j++ {
+ for k := 7; k >= 0; k-- {
+ symbol := SYMBOL_LOW
+ if (ws.pixels[i*ws.numColors+j] & (1 << uint(k))) != 0 {
+ symbol = SYMBOL_HIGH
+ }
+ for l := 2; l >= 0; l-- {
+ ws.pixBufUint[rpPos] &= ^(1 << uint(bitPos))
+ if (symbol & (1 << uint(l))) != 0 {
+ ws.pixBufUint[rpPos] |= 1 << uint(bitPos)
+ }
+ bitPos--
+ if bitPos < 0 {
+ rpPos += 2
+ bitPos = 31
+ }
+ }
+ }
+ }
+ }
+ }
+ ws.startDma()
  return nil
 }