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// Copyright 2022 Benjamin Barenblat
//
// Licensed under the Apache License, Version 2.0 (the "License"); you may not
// use this file except in compliance with the License. You may obtain a copy of
// the License at
//
// https://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
// License for the specific language governing permissions and limitations under
// the License.
package cfa635
import (
"encoding/binary"
"errors"
)
var (
errUnknownReportType = errors.New("failed to read report: unknown type")
errUnknownKey = errors.New("failed to read key activity report: unknown key")
errFBSCAB = errors.New("failed to read fan speed report: FBSCAB module disconnected")
errDOW = errors.New("failed to read temperature report: DOW sensor error")
)
// KeyActivity is a report that a key has been pressed or released.
type KeyActivity struct {
K Key
Pressed bool
}
// Key represents a button on the CFA635.
type Key int
const (
_ Key = iota
UpButton
DownButton
LeftButton
RightButton
EnterButton
ExitButton
)
// FanSpeed is a report on the speed of a system fan.
type FanSpeed struct {
N int
TachCycles int
TimerTicks int
}
// Temperature is a report on the system temperature.
type Temperature struct {
N int // Sensor number.
Celsius float64
}
// decodeReport converts a packet into either a *KeyActivity, a *FanSpeed, or a
// *Temperature, depending on the packet's type tag.
func decodeReport(p []byte) (any, error) {
switch p[0] {
case 0x80:
return decodeKeyActivity(p[2])
case 0x81:
return decodeFanSpeed(p[2:6])
case 0x82:
return decodeTemperature(p[2:6])
default:
return nil, errUnknownReportType
}
}
// decodeKeyActivity converts the data byte from a key activity report to a
// KeyActivity.
func decodeKeyActivity(b byte) (*KeyActivity, error) {
if b == 0 || b > 12 {
return nil, errUnknownKey
}
var a KeyActivity
if b < 7 {
a.Pressed = true
} else {
b -= 6
}
a.K = Key(b)
return &a, nil
}
// decodeFanSpeed converts the data part of a fan speed report packet to a
// FanSpeed.
func decodeFanSpeed(b []byte) (*FanSpeed, error) {
if b[1] == 0 && b[2] == 0 && b[3] == 0 {
return nil, errFBSCAB
}
return &FanSpeed{int(b[0]), int(b[1]), int(binary.BigEndian.Uint16(b[2:4]))}, nil
}
// decodeTemperature converts the data part of a temperature report packet to a
// Temperature.
func decodeTemperature(b []byte) (*Temperature, error) {
if b[3] == 0 {
return nil, errDOW
}
return &Temperature{int(b[0]), float64(binary.BigEndian.Uint16(b[1:3])) / 16}, nil
}
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