The USB temperature and temperature/humidity sensors sold my PCsensor are widely available from the parent site (http://pcsensor.com/usb-temperature-humidity.html), from Amazon, and from EBay.
There are several open source software projects that support these sensors, sometimes including complicated monitoring and graphing software. Unlike, these projects, the goal of this project is to simply read data from the sensors and do nothing else, given the following constraints:
- must work under Linux,
- must work with Python 3,
- third-party software will be avoided when possible,
- all third-party software must be provided as standard Debian packages.
I tried to use libusb (apt-get install python3-usb; "import usb.core") and it provides a sophisticated interface to USB devices that was very nice. Unfortunately, I have one thermometer that didn't work with raw usb and that required access via the hidraw device; and I have another thermometer that has an undocumented HID protocol, but that is accessible via a serial tty.
I tried using hid (apt-get install python3-hid) and hidapi (apt-get install python3-hidapi) and these worked ok for two of the thermometers I have, but not for the one that requires access via a serial tty.
Although HID devices are accessed directly, pySerial is used for TTYs. This module is available as a Debian package: sudo apt-get install python3-serial
I own five kinds of devices from PCsensors. These are all supported by temper.py.
In the following table "I" means the sensor is internal to the USB stick and "E" means the sensor is on a cable that is plugged into the USB stick.
| Product | Id | Firmware | Temp | Hum | Notes |
|---|---|---|---|---|---|
| TEMPer | 0c45:7401 | TEMPerF1.4 | I | Metal | |
| TEMPer | 413d:2107 | TEMPerGold_V3.1 | I | Metal | |
| TEMPerHUM | 413d:2107 | TEMPerX_V3.1 | I | I | White plastic |
| TEMPer2 | 413d:2107 | TEMPerX_V3.3 | I,E | White plastic | |
| TEMPer1F | 413d:2107 | TEMPerX_V3.3 | E | White plastic | |
| TEMPerX232 | 1a86:5523 | TEMPerX232_V2.0 | I,E | I | White plastic |
The 1a86:5523 device may identify as 413d:2107 depending on button presses, but it cannot be used successfully when in that mode.
If you try other software that uses libusb, the hidraw device may be disconnected. In this case, remove and re-insert the USB stick.
The TEMPer1F has only an external sensor, but it is not possible to detect that it is external, so it is reported as an internal temperature.
This is a metal USB stick marked "TEMPer" with thermometer logo on one side, and "TEMPer" on the other side. The end opposite the USB connector a screw hole. There is no humidity detector, but it appears water proof and I have submerged mine momentarily in ice water and in boiling water.
This is a white plastic USB stick marked "TEMPerHUM", "-40C - +85C", and "0-100%RH"; with blue button marked "TXT". On the reverse, "PCsensor". This model does not have a jack on the end.
When the button is pressed the red LED will blink as messages of the following style are sent (the temperature line repeats every second).
www.pcsensor.com
temperx v3.1
caps lock:on/off/++
num lock:off/on/--
type:inner-h2
inner-temperinner-humidityinterval
32.73 [c]36.82 [%rh]1s
When the button is pressed again, the LED will either be off or be solid red. This is the mode that temper.py uses.
physical description: White plastic USB stick marked "TEMPer2", "-40C - +125C"; with red button marked "TXT". On the reverse, "PCsensor". This model has a jack for an external sensor on the end.
notes: When the button is pressed, the red LED will blink as messages of the following form are sent (the temperature line repeats every second).
Without an external sensor:
www.pcsensor.com
temperx v3.3
caps lock:on/off/++
num lock:off/on/--
type:inner-tx
inner-tempinterval
27.93 [c]1s
With an external sensor:
www.pcsensor.com
temperx v3.3
caps lock:on/off/++
num lock:off/on/--
type:inner-tx;outer-tx
inner-tempintervalinterval
27.18 [c]29.62 [c]1s
This program uses the mode where the LED is either off or solid red.
White plastic USB stick marked "TEMPer1F", "-40C - +125C"; with pink button marked "TXT'. On the reverse, "PCsensor". This model has a jack for an external sensor and does not have an internal sensor.
When the button is pressed, the red LED will blink as messages of the following form are sent (the temperature line repeats every 1 second).
Without the probe inserted:
www.pcsensor.com
temperx v3.3
caps lock:on/off/++
num lock:off/on/--
type:unknown
1s
With the probe inserted:
www.pcsensor.com
temperx v3.3
caps lock:on/off/++
num lock:off/on/--
type:outer-tx
outer-tempinterval
24.93 [c]1s
This program uses the mode where the LED is either off or solid red.
White plastic USB stick marked "TEMPerX232", "0-100%RH", and "-40 - +85C"; with a green button marked "press". On the reverse, "PCsensor". On the end opposite the USB connector, there is a jack for an external temperature sensor (which I do not have and did not try).
When the button is pressed and held down until the red LED is solid, a blue LED will flash every second. In this mode, the USB vendor:product changes to 413d:2107, but only one HID device is available, and protocol sent to the hidraw device is rejected with an error.
When the LED is flashing blue, and the button is pressed momemtarily, the following are sent (the temperature line repeats every second).
www.PCsensor.com
TEMPerX232-V2.0
type:inner-H2
inner-temperinner-humidityinterval
30.48 [C]40.19 [%RH]1
When the button is pressed and held down until the red LED is solid, a green LED will flash every second. This is the mode temper.py uses. In this mode, if "Help" is sent to the serial device, the following will be sent back:
>>PCsensor<<
Welcome to use TEMPerX232!
Firmware Version:TEMPerX232_V2.0
The command is:
ReadTemp -->read temperature,temp_value = sensor_value + calibration
ReadCalib -->read calibration
SetCalib-type:xx.x,xx.x> -->set calibration, xx.x(-10.0~+10.0)
EraseFlash -->erase calibration
Version -->read firmware version
ReadType -->read the sensor type
ReadAlert-Temp -->read temp alert value
SetTempUpperAlert-type:xx.xx>-->set temp upper alert value,xx.xx(-40.00~+85.00)
SetTempLowerAlert-type:xx.xx>-->set temp lower alert value,xx.xx(-40.00~+85.00)
ReadAlert-Hum -->read hum alert value
SetHumUpperAlert-type:xx.xx> -->set hum upper alert value,xx.xx(00.00~99.99)
SetHumLowerAlert-type:xx.xx> -->set hum lower alert value,xx.xx(00.00~99.99)
SetMode-Temp:x> -->set tempmode, x(0~1)
ReadMode-Temp -->read tempmode
Help -->command help
? -->command help
The COM configuration is:
Mode: ASCII
Baud Rate: 9600bps
Data Bit: 8
Parity Bit: None
Stop Bit: 1
SHENZHEN RDing Tech CO.,LTD
www.PCsensor.com
This is the mode that temper.py uses. I was not successful getting this device to respond to any commands sent via the HID device.
I initially had trouble getting a reply to ReadTemp when using a terminal program (e.g., cu), but the example in the temper.py works without any problems, perhaps because no newline is sent after the comment.
$ ./temper.py --help
usage: temper.py [-h] [-l] [--json] [--force VENDOR_ID:PRODUCT_ID]
temper
optional arguments:
-h, --help show this help message and exit
-l, --list List all USB devices
--json Provide output as JSON
--force VENDOR_ID:PRODUCT_ID
Force the use of the hex id; ignore other ids
In this example, one of the devices doesn't have the HID driver attached because I was using an libusb-based program to access it.
$ ./temper.py -l
Bus 001 Dev 023 413d:2107 * ??? ['hidraw0', 'hidraw1']
Bus 001 Dev 086 0c45:7401 * TEMPerV1.4 []
Bus 002 Dev 002 04d8:f5fe TrueRNG ['ttyACM0']
In this example, one of the devices doesn't have the HID driver attached because I was using an libusb-based program to access it.
$ ./temper.py
Bus 001 Dev 023 413d:2107 TEMPerX_V3.1 26.55C 79.79F 43.41%
Bus 001 Dev 086 0c45:7401 Error: no hid/tty devices available
$ ./temper.py --json
[
{
"path": "/sys/bus/usb/devices/1-1.2",
"busnum": 1,
"devnum": 23,
"vendorid": 16701,
"productid": 8455,
"vendor_name": "",
"product_name": "",
"devices": [
"hidraw0",
"hidraw1"
],
"ident": "TEMPerX_V3.1",
"celsius": 26.55,
"fahrenheit": 79.78999999999999,
"humidity": 43.65
},
{
"path": "/sys/bus/usb/devices/1-1.1.1",
"busnum": 1,
"devnum": 86,
"vendorid": 3141,
"productid": 29697,
"vendor_name": "RDing",
"product_name": "TEMPerV1.4",
"devices": [
],
"error": "no hid/tty devices available"
}
]
Similar JSON output can be generated with the --list option.