forked from hybridgroup/gobot
/
sht3x_driver.go
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/
sht3x_driver.go
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/*
* Copyright (c) 2016-2017 Weston Schmidt <weston_schmidt@alumni.purdue.edu>
*
* 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
*
* http://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 i2c
// SHT3xDriver is a driver for the SHT3x-D based devices.
//
// This module was tested with AdaFruit Sensiron SHT32-D Breakout.
// https://www.adafruit.com/products/2857
import (
"errors"
"time"
"github.com/sigurn/crc8"
"gobot.io/x/gobot"
)
// SHT3xAddressA is the default address of device
const SHT3xAddressA = 0x44
// SHT3xAddressB is the optional address of device
const SHT3xAddressB = 0x45
// SHT3xAccuracyLow is the faster, but lower accuracy sample setting
const SHT3xAccuracyLow = 0x16
// SHT3xAccuracyMedium is the medium accuracy and speed sample setting
const SHT3xAccuracyMedium = 0x0b
// SHT3xAccuracyHigh is the high accuracy and slowest sample setting
const SHT3xAccuracyHigh = 0x00
var (
crc8Params = crc8.Params{0x31, 0xff, false, false, 0x00, 0xf7, "CRC-8/SENSIRON"}
ErrInvalidAccuracy = errors.New("Invalid accuracy")
ErrInvalidCrc = errors.New("Invalid crc")
ErrInvalidTemp = errors.New("Invalid temperature units")
)
// SHT3xDriver is a Driver for a SHT3x humidity and temperature sensor
type SHT3xDriver struct {
Units string
name string
connector Connector
connection Connection
Config
sht3xAddress int
accuracy byte
delay time.Duration
crcTable *crc8.Table
}
// NewSHT3xDriver creates a new driver with specified i2c interface
// Params:
// conn Connector - the Adaptor to use with this Driver
//
// Optional params:
// i2c.WithBus(int): bus to use with this driver
// i2c.WithAddress(int): address to use with this driver
//
func NewSHT3xDriver(a Connector, options ...func(Config)) *SHT3xDriver {
s := &SHT3xDriver{
Units: "C",
name: gobot.DefaultName("SHT3x"),
connector: a,
Config: NewConfig(),
sht3xAddress: SHT3xAddressA,
crcTable: crc8.MakeTable(crc8Params),
}
s.SetAccuracy(SHT3xAccuracyHigh)
for _, option := range options {
option(s)
}
return s
}
// Name returns the name for this Driver
func (s *SHT3xDriver) Name() string { return s.name }
// SetName sets the name for this Driver
func (s *SHT3xDriver) SetName(n string) { s.name = n }
// Connection returns the connection for this Driver
func (s *SHT3xDriver) Connection() gobot.Connection { return s.connector.(gobot.Connection) }
// Start initializes the SHT3x
func (s *SHT3xDriver) Start() (err error) {
bus := s.GetBusOrDefault(s.connector.GetDefaultBus())
address := s.GetAddressOrDefault(s.sht3xAddress)
s.connection, err = s.connector.GetConnection(address, bus)
return
}
// Halt returns true if devices is halted successfully
func (s *SHT3xDriver) Halt() (err error) { return }
// SetAddress sets the address of the device
func (s *SHT3xDriver) SetAddress(address int) { s.sht3xAddress = address }
// Accuracy returns the accuracy of the sampling
func (s *SHT3xDriver) Accuracy() byte { return s.accuracy }
// SetAccuracy sets the accuracy of the sampling
func (s *SHT3xDriver) SetAccuracy(a byte) (err error) {
switch a {
case SHT3xAccuracyLow:
s.delay = 5 * time.Millisecond // Actual max is 4, wait 1 ms longer
case SHT3xAccuracyMedium:
s.delay = 7 * time.Millisecond // Actual max is 6, wait 1 ms longer
case SHT3xAccuracyHigh:
s.delay = 16 * time.Millisecond // Actual max is 15, wait 1 ms longer
default:
err = ErrInvalidAccuracy
return
}
s.accuracy = a
return
}
// SerialNumber returns the serial number of the chip
func (s *SHT3xDriver) SerialNumber() (sn uint32, err error) {
ret, err := s.sendCommandDelayGetResponse([]byte{0x37, 0x80}, nil, 2)
if nil == err {
sn = (uint32(ret[0]) << 16) | uint32(ret[1])
}
return
}
// Heater returns true if the heater is enabled
func (s *SHT3xDriver) Heater() (status bool, err error) {
sr, err := s.getStatusRegister()
if err == nil {
if (1 << 13) == (sr & (1 << 13)) {
status = true
}
}
return
}
// SetHeater enables or disables the heater on the device
func (s *SHT3xDriver) SetHeater(enabled bool) (err error) {
out := []byte{0x30, 0x66}
if true == enabled {
out[1] = 0x6d
}
_, err = s.connection.Write(out)
return
}
// Sample returns the temperature in celsius and relative humidity for one sample
func (s *SHT3xDriver) Sample() (temp float32, rh float32, err error) {
ret, err := s.sendCommandDelayGetResponse([]byte{0x24, s.accuracy}, &s.delay, 2)
if nil != err {
return
}
// From the datasheet:
// RH = 100 * Srh / (2^16 - 1)
rhSample := uint64(ret[1])
rh = float32((uint64(1000000)*rhSample)/uint64(0xffff)) / 10000.0
tempSample := uint64(ret[0])
switch s.Units {
case "C":
// From the datasheet:
// T[C] = -45 + 175 * (St / (2^16 - 1))
temp = float32((uint64(1750000)*tempSample)/uint64(0xffff)-uint64(450000)) / 10000.0
case "F":
// From the datasheet:
// T[F] = -49 + 315 * (St / (2^16 - 1))
temp = float32((uint64(3150000)*tempSample)/uint64(0xffff)-uint64(490000)) / 10000.0
default:
err = ErrInvalidTemp
}
return
}
// getStatusRegister returns the device status register
func (s *SHT3xDriver) getStatusRegister() (status uint16, err error) {
ret, err := s.sendCommandDelayGetResponse([]byte{0xf3, 0x2d}, nil, 1)
if nil == err {
status = ret[0]
}
return
}
// sendCommandDelayGetResponse is a helper function to reduce duplicated code
func (s *SHT3xDriver) sendCommandDelayGetResponse(send []byte, delay *time.Duration, expect int) (read []uint16, err error) {
if _, err = s.connection.Write(send); err != nil {
return
}
if nil != delay {
time.Sleep(*delay)
}
buf := make([]byte, 3*expect)
got, err := s.connection.Read(buf)
if err != nil {
return
}
if got != (3 * expect) {
err = ErrNotEnoughBytes
return
}
read = make([]uint16, expect)
for i := 0; i < expect; i++ {
crc := crc8.Checksum(buf[i*3:i*3+2], s.crcTable)
if buf[i*3+2] != crc {
err = ErrInvalidCrc
return
}
read[i] = uint16(buf[i*3])<<8 | uint16(buf[i*3+1])
}
return
}