forked from kidoman/embd
/
tmp006.go
314 lines (273 loc) · 6.6 KB
/
tmp006.go
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// Package tmp006 allows interfacing with the TMP006 thermopile.
package tmp006
import (
"errors"
"fmt"
"math"
"sync"
"time"
"github.com/golang/glog"
"github.com/kidoman/embd"
)
const (
b0 = -0.0000294
b1 = -0.00000057
b2 = 0.00000000463
c2 = 13.4
tref = 298.15
a2 = -0.00001678
a1 = 0.00175
s0 = 6.4
vObjReg = 0x00
tempAmbReg = 0x01
configReg = 0x02
manIdReg = 0xFE
manId = 0x5449
devIdReg = 0xFF
devId = 0x0067
reset = 0x8000
modeOn = 0x7000
drdyEn = 0x0100
configRegDefault = modeOn | drdyEn
)
type SampleRate struct {
enabler uint16
samples int
timeRequired float64
}
var (
SR1 = &SampleRate{0x0000, 1, 0.25} // 1 sample, 0.25 second between measurements.
SR2 = &SampleRate{0x0200, 2, 0.5} // 2 samples, 0.5 second between measurements.
SR4 = &SampleRate{0x0400, 4, 1} // 4 samples, 1 second between measurements.
SR8 = &SampleRate{0x0600, 8, 2} // 8 samples, 2 seconds between measurements.
SR16 = &SampleRate{0x0800, 16, 4} // 16 samples, 4 seconds between measurements.
)
// TMP006 represents a TMP006 thermopile sensor.
type TMP006 struct {
// Bus to communicate over.
Bus embd.I2CBus
// Addr of the sensor.
Addr byte
// SampleRate specifies the sampling rate for the sensor.
SampleRate *SampleRate
initialized bool
mu sync.RWMutex
rawDieTemps chan float64
objTemps chan float64
closing chan chan struct{}
}
// New creates a new TMP006 sensor.
func New(bus embd.I2CBus, addr byte) *TMP006 {
return &TMP006{
Bus: bus,
Addr: addr,
}
}
func (d *TMP006) validate() error {
if d.Bus == nil {
return errors.New("tmp006: bus is nil")
}
if d.Addr == 0x00 {
return fmt.Errorf("tmp006: %#x is not a valid address", d.Addr)
}
return nil
}
// Close puts the device into low power mode.
func (d *TMP006) Close() error {
if err := d.setup(); err != nil {
return err
}
if d.closing != nil {
waitc := make(chan struct{})
d.closing <- waitc
<-waitc
}
glog.V(1).Infof("tmp006: resetting")
if err := d.Bus.WriteWordToReg(d.Addr, configReg, reset); err != nil {
return err
}
return nil
}
// Present checks if the device is present at the given address.
func (d *TMP006) Present() (bool, error) {
if err := d.validate(); err != nil {
return false, err
}
mid, err := d.Bus.ReadWordFromReg(d.Addr, manIdReg)
if err != nil {
return false, err
}
glog.V(1).Infof("tmp006: got manufacturer id %#04x", mid)
if mid != manId {
return false, fmt.Errorf("tmp006: not found at %#02x, manufacturer id mismatch", d.Addr)
}
did, err := d.Bus.ReadWordFromReg(d.Addr, devIdReg)
if err != nil {
return false, err
}
glog.V(1).Infof("tmp006: got device id %#04x", did)
if did != devId {
return false, fmt.Errorf("tmp006: not found at %#02x, device id mismatch", d.Addr)
}
return true, nil
}
func (d *TMP006) setup() error {
d.mu.RLock()
if d.initialized {
d.mu.RUnlock()
return nil
}
d.mu.RUnlock()
d.mu.Lock()
defer d.mu.Unlock()
if err := d.validate(); err != nil {
return err
}
if d.SampleRate == nil {
glog.V(1).Infof("tmp006: sample rate = nil, using SR16")
d.SampleRate = SR16
}
glog.V(1).Infof("tmp006: configuring with %#04x", configRegDefault|d.SampleRate.enabler)
if err := d.Bus.WriteWordToReg(d.Addr, configReg, configRegDefault|d.SampleRate.enabler); err != nil {
return err
}
d.initialized = true
return nil
}
func (d *TMP006) measureRawDieTemp() (float64, error) {
if err := d.setup(); err != nil {
return 0, err
}
raw, err := d.Bus.ReadWordFromReg(d.Addr, tempAmbReg)
if err != nil {
return 0, err
}
raw >>= 2
glog.V(2).Infof("tmp006: raw die temp %#04x", raw)
temp := float64(int16(raw)) * 0.03125
return temp, nil
}
func (d *TMP006) measureRawVoltage() (int16, error) {
if err := d.setup(); err != nil {
return 0, err
}
vlt, err := d.Bus.ReadWordFromReg(d.Addr, vObjReg)
if err != nil {
return 0, err
}
volt := int16(vlt)
glog.V(2).Infof("tmp006: raw voltage %#04x", volt)
return volt, nil
}
func (d *TMP006) measureObjTemp() (float64, error) {
if err := d.setup(); err != nil {
return 0, err
}
tDie, err := d.measureRawDieTemp()
if err != nil {
return 0, err
}
glog.V(2).Infof("tmp006: tdie = %.2f C", tDie)
tDie += 273.15 // Convert to K
vo, err := d.measureRawVoltage()
if err != nil {
return 0, err
}
vObj := float64(vo)
vObj *= 156.25 // 156.25 nV per LSB
vObj /= 1000 // nV -> uV
glog.V(2).Infof("tmp006: vObj = %.5f uV", vObj)
vObj /= 1000 // uV -> mV
vObj /= 1000 // mV -> V
tdie_tref := tDie - tref
s := 1 + a1*tdie_tref + a2*tdie_tref*tdie_tref
s *= s0
s /= 10000000
s /= 10000000
Vos := b0 + b1*tdie_tref + b2*tdie_tref*tdie_tref
fVobj := (vObj - Vos) + c2*(vObj-Vos)*(vObj-Vos)
temp := math.Sqrt(math.Sqrt(tDie*tDie*tDie*tDie + fVobj/s))
temp -= 273.15
return temp, nil
}
// RawDieTemp returns the current raw die temp reading.
func (d *TMP006) RawDieTemp() (float64, error) {
select {
case temp := <-d.rawDieTemps:
return temp, nil
default:
return d.measureRawDieTemp()
}
}
// RawDieTemps returns a channel to get future raw die temps from.
func (d *TMP006) RawDieTemps() <-chan float64 {
return d.rawDieTemps
}
// ObjTemp returns the current obj temp reading.
func (d *TMP006) ObjTemp() (float64, error) {
select {
case temp := <-d.objTemps:
return temp, nil
default:
return d.measureObjTemp()
}
}
// ObjTemps returns a channel to fetch obj temps from.
func (d *TMP006) ObjTemps() <-chan float64 {
return d.objTemps
}
// Start starts the data acquisition loop.
func (d *TMP006) Start() error {
if err := d.setup(); err != nil {
return err
}
d.rawDieTemps = make(chan float64)
d.objTemps = make(chan float64)
go func() {
var rawDieTemp, objTemp float64
var rdtAvlb, otAvlb bool
var err error
var timer <-chan time.Time
resetTimer := func() {
timer = time.After(time.Duration(d.SampleRate.timeRequired*1000) * time.Millisecond)
}
resetTimer()
for {
var rawDieTemps, objTemps chan float64
if rdtAvlb {
rawDieTemps = d.rawDieTemps
}
if otAvlb {
objTemps = d.objTemps
}
select {
case <-timer:
var rdt float64
if rdt, err = d.measureRawDieTemp(); err != nil {
glog.Errorf("tmp006: %v", err)
} else {
rawDieTemp = rdt
rdtAvlb = true
}
var ot float64
if ot, err = d.measureObjTemp(); err != nil {
glog.Errorf("tmp006: %v", err)
} else {
objTemp = ot
otAvlb = true
}
resetTimer()
case rawDieTemps <- rawDieTemp:
rdtAvlb = false
case objTemps <- objTemp:
otAvlb = false
case waitc := <-d.closing:
waitc <- struct{}{}
close(d.rawDieTemps)
close(d.objTemps)
return
}
}
}()
return nil
}