135 lines
3.3 KiB
Go
135 lines
3.3 KiB
Go
// Copyright 2017 The Periph Authors. All rights reserved.
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// Use of this source code is governed under the Apache License, Version 2.0
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// that can be found in the LICENSE file.
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package bcm283x
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import (
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"encoding/binary"
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"errors"
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"fmt"
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"periph.io/x/periph/conn/gpio/gpiostream"
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)
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// uint32ToBitLSBF packs a bit offset found on slice `d` (that is actually
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// uint32) back into a densely packed Bits stream.
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func uint32ToBitLSBF(w []byte, d []uint8, bit uint8, skip int) {
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// Little endian.
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x := bit / 8
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d = d[x:]
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bit -= 8 * x
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mask := uint8(1) << bit
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for i := range w {
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w[i] = ((d[0]&mask)>>bit<<0 |
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(d[skip*1]&mask)>>bit<<1 |
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(d[skip*2]&mask)>>bit<<2 |
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(d[skip*3]&mask)>>bit<<3 |
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(d[skip*4]&mask)>>bit<<4 |
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(d[skip*5]&mask)>>bit<<5 |
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(d[skip*6]&mask)>>bit<<6 |
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(d[skip*7]&mask)>>bit<<7)
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d = d[skip*8:]
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}
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}
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func getBit(b byte, index int, msb bool) byte {
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var shift uint
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if msb {
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shift = uint(7 - index)
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} else {
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shift = uint(index)
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}
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return (b >> shift) & 1
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}
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func raster32Bits(s gpiostream.Stream, skip int, clear, set []uint32, mask uint32) error {
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var msb bool
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var bits []byte
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switch b := s.(type) {
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case *gpiostream.BitStream:
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msb = !b.LSBF
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bits = b.Bits
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default:
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return fmt.Errorf("unsupported type %T", b)
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}
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m := len(clear) / 8
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if n := len(bits); n < m {
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m = n
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}
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index := 0
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for i := 0; i < m; i++ {
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for j := 0; j < 8; j++ {
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if getBit(bits[i], j, msb) != 0 {
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for k := 0; k < skip; k++ {
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set[index] |= mask
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index++
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}
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} else {
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for k := 0; k < skip; k++ {
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clear[index] |= mask
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index++
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}
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}
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}
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}
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return nil
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}
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// raster32 rasters the stream into a uint32 stream with the specified masks to
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// put in the correctly slice when the bit is set and when it is clear.
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//
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// `s` must be one of the types in this package.
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func raster32(s gpiostream.Stream, skip int, clear, set []uint32, mask uint32) error {
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if mask == 0 {
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return errors.New("bcm283x: mask is 0")
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}
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if len(clear) == 0 {
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return errors.New("bcm283x: clear buffer is empty")
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}
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if len(set) == 0 {
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return errors.New("bcm283x: set buffer is empty")
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}
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if len(clear) != len(set) {
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return errors.New("bcm283x: clear and set buffers have different length")
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}
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switch x := s.(type) {
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case *gpiostream.BitStream:
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// TODO
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return raster32Bits(x, skip, clear, set, mask)
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case *gpiostream.EdgeStream:
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return errors.New("bcm283x: EdgeStream is not supported yet")
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case *gpiostream.Program:
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return errors.New("bcm283x: Program is not supported yet")
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default:
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return errors.New("bcm283x: unknown stream type")
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}
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}
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// PCM/PWM DMA buf is encoded as little-endian and MSB first.
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func copyStreamToDMABuf(w gpiostream.Stream, dst []uint32) error {
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switch v := w.(type) {
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case *gpiostream.BitStream:
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if v.LSBF {
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return errors.New("TODO(simokawa): handle BitStream.LSBF")
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}
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// This is big-endian and MSB first.
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i := 0
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for ; i < len(v.Bits)/4; i++ {
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dst[i] = binary.BigEndian.Uint32(v.Bits[i*4:])
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}
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last := uint32(0)
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if mod := len(v.Bits) % 4; mod > 0 {
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for j := 0; j < mod; j++ {
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last |= (uint32(v.Bits[i*4+j])) << uint32(8*(3-j))
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}
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dst[i] = last
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}
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return nil
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case *gpiostream.EdgeStream:
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return errors.New("TODO(simokawa): handle EdgeStream")
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default:
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return errors.New("unsupported Stream type")
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}
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}
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