0c45:7402 Temperature reading incorrect

[nikcross]

I have a TEMPerHUM temperature and humidity sensor connected to a Raspberry Pi
lsusb gives me:
0c45:7402 Microdia TEMPerHUM Temperature & Humidity Sensor

temper-poll gives me:
Found 1 devices
Device #0: 106.5°C 223.6°F

Its warm in here, but not that warm :-) and there is no humidity value.

I also have a TEMPer and that works ok.

Any ideas ?

[MatGit5]

Same issue here...
Device #0: 109.4°C 228.9°F
The temperature is actually below 21°C.

[davet2001]

Quite likely it is an unrecognised sensor type.
Please can you paste the output of
lsusb -v -d 0c45:7402

[MatGit5]

lsusb -v -d 0c45:7402

Bus 001 Device 004: ID 0c45:7402 Microdia TEMPerHUM Temperature & Humidity Sensor
Device Descriptor:
bLength 18
bDescriptorType 1
bcdUSB 2.00
bDeviceClass 0
bDeviceSubClass 0
bDeviceProtocol 0
bMaxPacketSize0 8
idVendor 0x0c45 Microdia
idProduct 0x7402 TEMPerHUM Temperature & Humidity Sensor
bcdDevice 0.01
iManufacturer 1 RDing
iProduct 2 TEMPERHUM1V1.2
iSerial 0
bNumConfigurations 1
Configuration Descriptor:
bLength 9
bDescriptorType 2
wTotalLength 0x003b
bNumInterfaces 2
bConfigurationValue 1
iConfiguration 0
bmAttributes 0xa0
(Bus Powered)
Remote Wakeup
MaxPower 100mA
Interface Descriptor:
bLength 9
bDescriptorType 4
bInterfaceNumber 0
bAlternateSetting 0
bNumEndpoints 1
bInterfaceClass 3 Human Interface Device
bInterfaceSubClass 1 Boot Interface Subclass
bInterfaceProtocol 1 Keyboard
iInterface 0
HID Device Descriptor:
bLength 9
bDescriptorType 33
bcdHID 1.10
bCountryCode 0 Not supported
bNumDescriptors 1
bDescriptorType 34 Report
wDescriptorLength 65
Report Descriptor: (length is 65)
Item(Global): Usage Page, data= [ 0x01 ] 1
Generic Desktop Controls
Item(Local ): Usage, data= [ 0x06 ] 6
Keyboard
Item(Main ): Collection, data= [ 0x01 ] 1
Application
Item(Global): Report ID, data= [ 0x01 ] 1
Item(Global): Usage Page, data= [ 0x07 ] 7
Keyboard
Item(Local ): Usage Minimum, data= [ 0xe0 ] 224
Control Left
Item(Local ): Usage Maximum, data= [ 0xe7 ] 231
GUI Right
Item(Global): Logical Minimum, data= [ 0x00 ] 0
Item(Global): Logical Maximum, data= [ 0x01 ] 1
Item(Global): Report Size, data= [ 0x01 ] 1
Item(Global): Report Count, data= [ 0x08 ] 8
Item(Main ): Input, data= [ 0x02 ] 2
Data Variable Absolute No_Wrap Linear
Preferred_State No_Null_Position Non_Volatile Bitfield
Item(Global): Report Count, data= [ 0x01 ] 1
Item(Global): Report Size, data= [ 0x08 ] 8
Item(Main ): Input, data= [ 0x01 ] 1
Constant Array Absolute No_Wrap Linear
Preferred_State No_Null_Position Non_Volatile Bitfield
Item(Global): Report Count, data= [ 0x03 ] 3
Item(Global): Report Size, data= [ 0x01 ] 1
Item(Global): Usage Page, data= [ 0x08 ] 8
LEDs
Item(Local ): Usage Minimum, data= [ 0x01 ] 1
NumLock
Item(Local ): Usage Maximum, data= [ 0x03 ] 3
Scroll Lock
Item(Main ): Output, data= [ 0x02 ] 2
Data Variable Absolute No_Wrap Linear
Preferred_State No_Null_Position Non_Volatile Bitfield
Item(Global): Report Count, data= [ 0x05 ] 5
Item(Global): Report Size, data= [ 0x01 ] 1
Item(Main ): Output, data= [ 0x01 ] 1
Constant Array Absolute No_Wrap Linear
Preferred_State No_Null_Position Non_Volatile Bitfield
Item(Global): Report Count, data= [ 0x05 ] 5
Item(Global): Report Size, data= [ 0x08 ] 8
Item(Global): Logical Minimum, data= [ 0x00 ] 0
Item(Global): Logical Maximum, data= [ 0xff ] 255
Item(Global): Usage Page, data= [ 0x07 ] 7
Keyboard
Item(Local ): Usage Minimum, data= [ 0x00 ] 0
No Event
Item(Local ): Usage Maximum, data= [ 0xff ] 255
(null)
Item(Main ): Input, data= [ 0x00 ] 0
Data Array Absolute No_Wrap Linear
Preferred_State No_Null_Position Non_Volatile Bitfield
Item(Main ): End Collection, data=none
Endpoint Descriptor:
bLength 7
bDescriptorType 5
bEndpointAddress 0x81 EP 1 IN
bmAttributes 3
Transfer Type Interrupt
Synch Type None
Usage Type Data
wMaxPacketSize 0x0008 1x 8 bytes
bInterval 10
Interface Descriptor:
bLength 9
bDescriptorType 4
bInterfaceNumber 1
bAlternateSetting 0
bNumEndpoints 1
bInterfaceClass 3 Human Interface Device
bInterfaceSubClass 1 Boot Interface Subclass
bInterfaceProtocol 2 Mouse
iInterface 0
HID Device Descriptor:
bLength 9
bDescriptorType 33
bcdHID 1.10
bCountryCode 0 Not supported
bNumDescriptors 1
bDescriptorType 34 Report
wDescriptorLength 41
Report Descriptor: (length is 41)
Item(Global): Usage Page, data= [ 0x00 0xff ] 65280
(null)
Item(Local ): Usage, data= [ 0x01 ] 1
(null)
Item(Main ): Collection, data= [ 0x01 ] 1
Application
Item(Local ): Usage, data= [ 0x01 ] 1
(null)
Item(Global): Logical Minimum, data= [ 0x00 ] 0
Item(Global): Logical Maximum, data= [ 0xff 0x00 ] 255
Item(Global): Report Size, data= [ 0x08 ] 8
Item(Global): Report Count, data= [ 0x08 ] 8
Item(Main ): Input, data= [ 0x02 ] 2
Data Variable Absolute No_Wrap Linear
Preferred_State No_Null_Position Non_Volatile Bitfield
Item(Local ): Usage, data= [ 0x01 ] 1
(null)
Item(Global): Report Count, data= [ 0x08 ] 8
Item(Main ): Output, data= [ 0x02 ] 2
Data Variable Absolute No_Wrap Linear
Preferred_State No_Null_Position Non_Volatile Bitfield
Item(Global): Usage Page, data= [ 0x0c ] 12
Consumer
Item(Local ): Usage, data= [ 0x00 ] 0
Unassigned
Item(Global): Logical Minimum, data= [ 0x80 ] 128
Item(Global): Logical Maximum, data= [ 0x7f ] 127
Item(Global): Report Size, data= [ 0x08 ] 8
Item(Global): Report Count, data= [ 0x08 ] 8
Item(Main ): Feature, data= [ 0x02 ] 2
Data Variable Absolute No_Wrap Linear
Preferred_State No_Null_Position Non_Volatile Bitfield
Item(Main ): End Collection, data=none
Endpoint Descriptor:
bLength 7
bDescriptorType 5
bEndpointAddress 0x82 EP 2 IN
bmAttributes 3
Transfer Type Interrupt
Synch Type None
Usage Type Data
wMaxPacketSize 0x0008 1x 8 bytes
bInterval 10
can't get device qualifier: Resource temporarily unavailable
can't get debug descriptor: Resource temporarily unavailable
Device Status: 0x0000
(Bus Powered)

[davet2001]

Yes, it looks like 'TEMPERHUM1V1.2' is not supported yet by the python package, but 'TEMPERHUM1V1.3' is. There is a high chance that they behave the same. Testing it should be a matter of editing temper.py and listing 'TEMPERHUM1V1.2' in each of the places where you see 'TEMPERHUM1V1.3'.

Unfortunately the package is a bit piecemeal with not all of the sensor data in one place, see #97. But that shouldn't stop you getting it working.

[davet2001]

I have made a guess at config settings for this device:

davet2001@728c977

Maybe you could download and try it?

[davet2001]

Did it work @MatGit5 ?

[skilleter]

I've also got one of these and the suggested patch nearly works.

The device has a button which causes to emulate a keyboard and output temperature and humidity readings as if they'd been typed in.

With this active it reports a temperature of 25.31°C and a relative humidity of 40.71 and, by comparison, the cli.py script reports the temperature as 25.3°C and the humidity as 35.1, so temperature is correct and humidity is about 5.5% low (allowing for the fact that the keyboard emulation doesn't work on Windows, so I had to keep swapping it between Windows and Linux machines to get the readings).

[davet2001]

@skilleter There's a possibility that it's working fine, but let's check.

Please could you checkout
davet2001@a2c35d5

and run:
python3 -m temperusb.cli -v

Please reply back with the full console output.

Then press the button again and report what it displays in keyboard mode. Try to keep time between the two as short as possible and use a plastic object (e.g. pen) to press the button to prevent your hand from heating up the device.

[skilleter]

Output from the script:
$ python3 -m temperusb.cli -v
DEBUG:temperusb.temper:Found device | Bus:1 Ports:10 SensorCount:1
INFO:temperusb.temper:Found 1 TEMPer devices
Found 1 devices
DEBUG:temperusb.temper:Detaching kernel driver for interface 0 of <DEVICE ID 0c45:7402 on Bus 001 Address 006> on ports 10
DEBUG:temperusb.temper:Detaching kernel driver for interface 1 of <DEVICE ID 0c45:7402 on Bus 001 Address 006> on ports 10
DEBUG:temperusb.temper:Ctrl transfer: b'\x01\x803\x01\x00\x00\x00\x00'
DEBUG:temperusb.temper:Read data: '80 04 62 e4 5f c2 60 3f'
DEBUG:temperusb.temper:Ctrl transfer: b'\x01\x803\x01\x00\x00\x00\x00'
DEBUG:temperusb.temper:Read data: '80 04 62 dc 5f c2 60 3f'
DEBUG:temperusb.temper:ID='TEMPERHUM1V1.2'
DEBUG:temperusb.temper:T=21.00769C
DEBUG:temperusb.temper:Ctrl transfer: b'\x01\x803\x01\x00\x00\x00\x00'
DEBUG:temperusb.temper:Read data: '80 04 62 dc 5f c2 60 3f'
DEBUG:temperusb.temper:Ctrl transfer: b'\x01\x803\x01\x00\x00\x00\x00'
DEBUG:temperusb.temper:Read data: '80 04 62 dc 5f c2 60 3f'
DEBUG:temperusb.temper:ID='TEMPERHUM1V1.2'
DEBUG:temperusb.temper:RH=40.75674%
Device #0: 21.0°C 69.8°F 40.8%RH

Output in keyboard mode with button-pressing performed as requested (and done on the same computer now that I've found it works if it isn't connected via a hub):

www.pcsensor.com
type:hum
caps lock:on/off/++ fw:1.2
num lock:off/on/--
c %rh interval
; : 20.92 46.07 01
; : 20.94 46.26 01
; : 20.95 46.26 01
; : 20.96 46.44 01

[davet2001]

Ok, assuming the measuring IC is an si7021 the datasheet gives formula

So in the returned data '80 04 62 dc 5f c2 60 3f' at offset 4 we have:
0x5f 0xc2
which is 0d24514
So %RH should be (125*24514)/65536 - 6 = 40.75674438

Someone else also reports that the same device reads a bit high for humidity.

It is possible (not proven - I'm just speculating), that the keyboard mode output is accidentally omitting the -6 in the calculation, outputting 46.07% RH when it should be 40.07%, and that this could be an issue with the device itself rather than temper-python.

Please note, some caveats:

• it's only a 12bit ADC inside so the last 4 bits of the 16bit reading are probably meaningless anyway (that's about 0.0305%RH)
• The datasheet spec is only +/-3% RH.
• Things like poor design of power supply loading/decoupling are not to be underestimated in these cheap devices. For example I wouldn't be surprised if the LED on/off status influences the reading.

I don't have one so I can't check, but it would be helpful if anyone is willing to open the device and read the IC markings to verify that it is actually an SI7021.

Also comparing the readings to an independent known good sensor would be helpful for a true RH ref.

In summary: temper-python seems to be handling the calculation correctly. Would help to confirm the sensor type and true RH being measured.

[davet2001]

Unless anyone objects, I propose merging this as it improves functionality. A follow up PR could be added if someone can see a way to genuinely improve accuracy.

[endolith]

I don't have one so I can't check, but it would be helpful if anyone is willing to open the device and read the IC markings to verify that it is actually an SI7021.

Also comparing the readings to an independent known good sensor would be helpful for a true RH ref.

I could open mine if needed, but edorfaus/TEMPered#30 says it's Si7021 and has photos like this:

Mine is

0x0C45	idVendor
0x7402	idProduct
0x0001	bcdDevice
0x01	iManufacturer   "RDing"
0x02	iProduct        "TEMPERHUM1V1.3"

I also have a USB Protocol Analyzer and logic analyzer if that's helpful.

[endolith]

Oh wait, mine is already supported. Nevermind.

Yes, it looks like 'TEMPERHUM1V1.2' is not supported yet by the python package, but 'TEMPERHUM1V1.3' is.

[skilleter]

I'm happy for this to be merged. I had a go at opening the case for my sensor and was defeated by it, I'm afraid. The amount of force I was applying was heading dangerously towards 'one slip with the screwdriver and there will be blood everywhere' territory!