107 lines
3.0 KiB
Go
107 lines
3.0 KiB
Go
//--------------------------------------------------------------------------------------------------
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//
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// Copyright (c) 2018 Denis Dyakov
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//
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// Permission is hereby granted, free of charge, to any person obtaining a copy of this software and
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// associated documentation files (the "Software"), to deal in the Software without restriction,
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// including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense,
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// and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so,
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// subject to the following conditions:
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//
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// The above copyright notice and this permission notice shall be included in all copies or substantial
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// portions of the Software.
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//
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// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING
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// BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
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// NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
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// DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
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//
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//--------------------------------------------------------------------------------------------------
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package bh1750
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import (
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"bytes"
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"encoding/binary"
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"math"
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i2c "github.com/d2r2/go-i2c"
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)
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// Utility functions
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// getS16BE extract 2-byte integer as signed big-endian.
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func getS16BE(buf []byte) int16 {
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v := int16(buf[0])<<8 + int16(buf[1])
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return v
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}
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// getS16LE extract 2-byte integer as signed little-endian.
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func getS16LE(buf []byte) int16 {
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w := getS16BE(buf)
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// exchange bytes
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v := (w&0xFF)<<8 + w>>8
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return v
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}
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// getU16BE extract 2-byte integer as unsigned big-endian.
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func getU16BE(buf []byte) uint16 {
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v := uint16(buf[0])<<8 + uint16(buf[1])
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return v
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}
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// getU16LE extract 2-byte integer as unsigned little-endian.
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func getU16LE(buf []byte) uint16 {
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w := getU16BE(buf)
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// exchange bytes
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v := (w&0xFF)<<8 + w>>8
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return v
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}
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func calcCRC1(seed byte, buf []byte) byte {
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for i := 0; i < len(buf); i++ {
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b := buf[ /*len(buf)-1-*/ i]
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for j := 0; j < 8; j++ {
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if (seed^b)&0x01 != 0 {
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seed ^= 0x18
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seed >>= 1
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seed |= 0x80
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// crc = crc ^ 0x8c
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} else {
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seed >>= 1
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}
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b >>= 1
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}
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}
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return seed
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}
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// Round float amount to certain precision.
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func round64(value float64, precision int) float64 {
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value2 := math.Round(value*math.Pow10(precision)) /
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math.Pow10(precision)
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return value2
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}
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// Round float amount to certain precision.
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func round32(value float32, precision int) float32 {
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return float32(round64(float64(value), precision))
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}
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// Read byte block from i2c device to struct object.
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func readDataToStruct(i2c *i2c.I2C, byteCount int,
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byteOrder binary.ByteOrder, obj interface{}) error {
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buf1 := make([]byte, byteCount)
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_, err := i2c.ReadBytes(buf1)
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if err != nil {
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return err
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}
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buf := bytes.NewBuffer(buf1)
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err = binary.Read(buf, byteOrder, obj)
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if err != nil {
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return err
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}
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return nil
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}
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