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DXL360S digital angle meter (0.01 degree) USB interface?

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JBeale:
Admittedly, this is a rather obscure question.

I got a DXL360S digital inclinometer / angle meter, which has an advertised measurement resolution of 0.01 degree and accuracy of 0.05 degree (in the range 0..20 and 70..90 degrees). I've learned be skeptical of some claims but to my surprise, for small angles it is actually repeatable to +/- 0.02 degrees in my testing, maybe even 0.01 if you average over a reasonable length of time. Given that 0.01 degree is only 36 arc-seconds, I'm also not sure if my house is stable at that level in a sub-second time interval. It has about 4 readings per second and seems faster to respond than a precision bubble level. Anyway, the user display works fine.

Interestingly this specific device has a USB port, not just for charging but (allegedly) with the measured angle data output as a serial device. The unlabelled, unbranded instruction manual says to see website for USB connection. Of course there is no hint of such a website listed anywhere in the manual, or online that I can find. I realize this is a longshot, but has anyone ever tried to connect to this thing?

Windows sees nothing. Linux reports "device descriptor read/64, error -71, Device not responding to setup address. Cannot enable." My USB cable is known-good. The reason I'm bothering to ask is that I have some a vague thought this might not be simply a broken device, but some nonstandard USB implementation that someone found good enough for its original, factory internal use using some kind of homebrew software, and the designer didn't really plan for it to be used externally.

This is the product listing I bought it from: https://www.amazon.com/dp/B077T7XW7X
Here's an online copy of the same user manual provided in paper form with the device:
https://www.roeckle.com/WebRoot/Store13/Shops/62116134/5EB6/6EBD/9A39/4D35/9E28/0A0C/6D12/406A/DXL360S_v2-Dual_Axis_Digital_Protractors.pdf

"PC Communication It has a PC data logging function. For DXL360S you can directly plug the USB cable between PC and protractor by mini USB cable Specification:
1) RS232 Com Port 9600 baud rate
2) USB connection ( include a RS232 to USB adapter)
3) Format will output ASCII: example for x is 0, Y is -88.88 X+0000Y-8888
Detail can visit our website or contact our sales person."

Output from 'dmesg' on Linux connection:


--- Code: ---[3490370.560370] usb 1-6: new low-speed USB device number 33 using xhci_hcd
[3490370.688363] usb 1-6: device descriptor read/64, error -71
[3490370.924265] usb 1-6: device descriptor read/64, error -71
[3490371.164217] usb 1-6: new low-speed USB device number 34 using xhci_hcd
[3490371.296340] usb 1-6: device descriptor read/64, error -71
[3490371.532453] usb 1-6: device descriptor read/64, error -71
[3490371.640476] usb usb1-port6: attempt power cycle
[3490372.052252] usb 1-6: new low-speed USB device number 35 using xhci_hcd
[3490372.052779] usb 1-6: Device not responding to setup address.
[3490372.260434] usb 1-6: Device not responding to setup address.
[3490372.468407] usb 1-6: device not accepting address 35, error -71
[3490374.268375] usb usb1-port6: Cannot enable. Maybe the USB cable is bad?
[3490374.268473] usb usb1-port6: unable to enumerate USB device
--- End code ---

ataradov:
I bet is not a USB port, but UART exposed on the USB data pins. And the USB part is in the proprietary cable.

Use a logic analyzer or a scope and check D+/D- pins.

Or if you can disassemble it without too much damage, do that and check what is on the inside.

The fact that it thinks it is a low speed device is also a hint. UART just created a high idle level on the D- line and the host thinks it is a pull-up resistor. There are no LS USB to RS232 ICs that are currently manufactured.

JBeale:
Yes, you are exactly correct. I modified a USB cable to check, and found that the white wire (USB D-) is carrying a 3.3V logic level UART output signal at 9600 bps, giving me four ASCII digits each for X and Y readings, and the readings are sent at irregular intervals but overall approximately 10 per second. I did not expect a regular UART signal on a standard USB plug. However knowing this I can make use of it. Thank you!

JBeale:
In case of interest, here's a video testing this sensor with a machinist type rotation stage (rotary platform). I am driving the stage to nominally 2.0, 5.0, 10.0 and 15.0 degrees off level. The sensor is good enough that I don't actually know whether it is more accurate than my ebay rotation stage. It actually seems to beat its 0.05 degree accuracy spec, so that is not too bad given its price, in my opinion.  Some years ago I don't recall any digital readout, 360 degree, 0.01 degree resolution level sensor device being available at all, at least at a consumer level.

todd_fuller:
I've had this angle cube for a number of years. It's OK. I have some neat features like mm per meter reading. While it has a good response time, there's very little internal filtering so the value bounces around unless you're very smooth with the adjustment. I wouldn't recommend this for anything by hand for this reason. It also claims that it can measure angles with the internal gyro and that's partially true.

The biggest problem I had with this angle cube is that the faces are not perpendicular or parallel with one another. So you need to be thoughtful about what face you zero against. Since the case is plastic, it's just not well suited for that kind of usage.

This is the OEM website:
http://www.jingyan-tech.com/en/html/product/28.html

Recently, I picked up a different angle cube from iGaging. Has USB output + a wireless version. Sides are 90 degrees, response time is good but doesn't jump all over the place. Similar but not as good accuracy specifications. Claim 0.05 degree reading, 0.2 degree accuracy. Doesn't have all the features of the DXL360 but day-to-day usage is better.

http://www.igaging.com/ip54-anglecube-angle-gauges.html

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