Over the past two days, I am doing some reading on how to get data over USB from an external device which has no device driver installed. I have to read data from a WT500 Yokogawa Power Meter (basically I want to read just one of the parameter that the meter shows, just the power values) over USB. I am aware that a device driver for WT500 is available, but it has some dependencies and I do not want to install a software or change anything majorly in our node to cater to that.
I have found that libusb could be used to perform what I would want, and I have a C program that sniffs the USB device and returns some information. I have looked into usb-robot as well, which also uses libusb. The server node that I am probing has OpenSUSE Linux kernel 2.6.30. I have usbfs mounted.
Question:
I am expecting that using libusb, I would be able to get data dumps from the power meter whenever I request, via usb device. Can I request the meter something like - send 25k of data, and then upon parsing it, I get the parameter value that I am looking for? Considering that I have zero knowledge about the device, can I get some meaningful values out of it? An example code would help.
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There are some standard messages like ?IDN with which a USBTMC device could be queried. However, specific queries need to be sent to a meter (the syntax should be there in the technical doc/manual/communication interface) if one needs to get whatever is showing up on screen.
I guess there are no easier ways of doing what I want - like just reading a file using something like fread ??
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Yes, almost. If USBTMC module is installed (the default one in our kernel did not work, detailed explanation of installing and querying a device is here - http://code.google.com/p/scte/wiki/USBTMC), then one just needs to send some queries and read the response via cat or something from the specific files under /dev.
From the meter technical document, I see that the driver communication interface that is described is Windows specific, so I reckon I might need to do some reverse engineering.
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Yes, but only a tiny bit or may be not at all.
Thank you.
EDIT: After a bit of googling I think I have the answers, I have added them next to the questions I asked.
Related
I was able to make a working HID USB stack on my "StartUSB for PIC" board for the 18F2550 microcontroller. I based it on one of the MLA libraries, which was made for the 18F45K50 (MLA 2018_11_26, hid_custom, picdem_fs_usb_k50.x), but I converted it to work with the 18F2550 (there might have been easier ways, but only learned to work with PIC about 1 month ago). On the host side, I'm using LibUsbDotNet (also here, there might be easier ways - the documentation on this library really sucks) on a Windows 10 machine.
I'm using the HID class, full speed, and all seems to work. Although, I get some random errors on the host PC (see below), but doing one close/re-open cycle on the host side when getting the error is kind of solving it. Dirty, but it works. So I kind of ignore this now.
Win32Error:Win32Error:GetOverlappedResult Ep 0x01
995:The I/O operation has been aborted because of either a thread exit or an application request.
I'm not an expert on USB (yet). But all examples I'm seeing are based on 1) you send first a command to the device and 2) then you retrieve the answer from the device. I did some performance tests, and see that this indeed shows that I can do about 500 cycles/second. I think that is correct, because each cycle, sending command and retrieving answer, each takes 1 msec.
But do I really need to send a command? Can't I just keep reading endlessly, and when the device has somthing to say, it does send the data in an IN transaction, and when not it ignores which creates a timeout on the host side. That would mean that I can poll at 1000 cycles/second? Unfortunately, I have tried it by changing my implementation on the PIC, but I get very weird results. I think I have issues with suspend mode. That brings me to another question - how can I make the device get out of suspend mode (means that not the host, but the device should be triggering this event). I have searched the MLA library for command such as "wakeup", "resume", ... but couldn't find anything.
So, to summarize, 2 questions:
Conceptual: Can I send data from device to host without being requested for it by a command from the host?
For PIC experts: How can I have a device trigger for a wakeup from suspend mode?
And indeed, the answer is Yes on the first question.
In the meantime, I found another link on the web that contains a Visual Studio C# implementation of a USB library including all the source files.
If you're interested, this is the link
This C# host implementation works as a charm. Without sending a command to the device, I get notified immediately if a button is pressed. Great!
It also proofs that my earlier device implementation based on the original MicroChip MLA, is 100% correct. I stress tested the implementation by sending a "toggle LED command" as fast as I could, and I reach 1000 commands/second. Again great!
I think that LibUsbDotNet isn't that perfect after all. As I wrote above, I get rather unstable communication (Win32Error). But with this implementation, I don't get a single error, even after running for half an hour # 1000 commands/second.
So for me, case closed.
I have an infrared thermometer which operates on a virtual serial port over USB, which I am trying to use on a Linux intel and next on a raspberry Pi. The system did not enumerate a /dev/ttyUSB device.
I found a piece of a solution here :
Cygnal Integrated Products serial port on Linux
I reprogrammed the product_ID and can now see it as /dev/ttyUSB0.
But trying to talk to the thermometer with minicom doesn't work.
minicom keeps saying "disconnected" despite the "9600 8N1" indication.
I must say, I had many attempt to work with this kind of communication over USB/serial adapter trying using many different terminal emulator like screen or minicom but without any success at all !
I'm not even sure about the right way to send request and receive data.
Here is the documentation I'm using trying to talk to the thermometer :
http://www.optris.com/interfaces?file=tl_files/downloads/Manuals/addendums-de-en/ct-ctlaser-commands.pdf
Edit :
I'm now trying to use PySerial Python library in a Python script with an Arduino as a target (to act as my thermometer, the arduino runs a simple code that takes the data received and send them back to my Python console.) But still, there is so many confusion possible between ASCII, Hexa, binary, that I'm not capable of debugging anything as I don't know where the transformation between different format takes place !
The communication is working as I can get some data forth and back from my Python console through the Arduino. But I can't get sending hexadecimal data and getting any response back in hexadecimal format. + You say "Your latest question puts you in the off-topic category. ", what do you mean ? Sorry of being so confused.
In my current scenario, I'm using NETLIGHT Pin (Pin no. 64) of SIM800 module with my PIC microcontroller to know whether my module is registered or not?
This way I built the circuit. Just I removed LED from VBAT. Then I connect collected of NPN transistor to pic micro input PIN.
I want to know whether any easy way using AT commands to find network registration status of SIM800?
Unfortunalty it's seem not to be really possible (or in fact detecting this state in only one way)
I use SIM800 and let it run for hours and I have seen many cases of network loose, while the AT+CREG? continue telling everything is OK.
Also, even with network down, the SIM800 continue sending you the name of the operator and the strengh of the signal.
The only way I've found is to monitor the serial port: when the SIM800 loose the network, it sends two messages:
+PDP: DEACT and
+SAPBR 1: DEACT
I suggest you to have a look at the document "SIM800 Series_AT Command Manual" and especially the chapter "19.3 Summary of Unsolicited Result Codes". You'll find +PDP and other interesting code (like under-voltage warning, DNS failed...) and see some of these messages are not linked to AT command.
From the manufacturer's documentation:
I've worked with WPD API for a while now, and I seem to run in to problem after problem.
Once I fix one problem, something else pops up. But hey, that's life.
I've been trying to determine if a WPD device is a storage device or a phone or whatever.
Turns out, devices such as iPhone are not set to be recognized as a phone, but instead as a generic device in terms of WPD_DEVICE_TYPE.
But, it is presented to Windows as a storage device.
When connecting external harddrives, SD memory card readers and other more conventional storage devices, they are recognized by the WPD API as well, but ehy that also get a dedicated mount point in Windows.
If I connect an external harddrive, it will have one functional category object, and the value of that object will be the path of that drive, say E:.
Nice. Great!
So my question is: How can I somehow read if the WPD device has a mountpoint?
Sure the functional object indicates that it has one, but is it possible that there could be an indicational value which states that a mount point is available?
Check the device Ids, here's an example how they differ:
\\?\swd#wpdbusenum#_??_usbstor#disk&ven_usb&prod_flash_disk&rev_1100#aa04012700007404&0#{53f56307-b6bf-11d0-94f2-00a0c91efb8b}#{6ac27878-a6fa-4155-ba85-f98f491d4f33
vs.
USBSTOR\DISK&VEN_USB&PROD_FLASH_DISK&REV_1100\AA04012700007404&0
The upper one is the Id gathered from PortableDeviceManagerClass (first step to create an PortableDevice object), the lower one I've just read from the Device Manager, but it should be easily retrievable with one of these solutions:
How do I get a Unique Identifier for a Device within Windows 10 Universal?
https://sourceforge.net/projects/sharpdevelop/files/SharpUSBLib/
I'm trying to create an embedded outdoor display of bus arrival times at my university. I'd like the device to utilize my school's secured WiFi network to show arrival time updates determined from a server script I have running.
I was hoping to get some advice on the high-level operation of this thing -- would it be better for the display board to poll a hosted database via the WiFi network or should I have a script try to communicate with the board directly over 802.11? (Push or Pull?)
I was planning to use a Wifly or WIZnet ethernet board in combination with a wireless access hub. Mostly inspired by this project: http://www.circuitcellar.com/Wiznet/winners/001166.html Would anyone recommend something else over one of the WIZnet boards? I saw SPI/UART options and thought these boards could work with an AVR platform.
And out of curiosity -- if you were to 'cold start' this device (ie, request a bus arrival time by pushing the display's on button) you might expect it to take 10-20 seconds to get assigned an IP and successfully connect to the database, does that sound right?
I'd go pull. In fact, I'd have outdoor display make http or https requests of the server. That way the server could tell it how long to show a given set of data before polling for a new one using standard http page expiration.
I think pull would make it easier to have multiple displays, and to test your server as well. I've also got a gut feeling that this would make your display more secure. Someone would have to hack your server to hijack your display.
There's a very cool looking Arduino-targetted product called the WiShield. Seems super easy to use and he provides some source code. It uses SPI for host communication. If you're not interested in going the Arduino route, I'm sure the source code wouldn't be too hard to port to something like avr-gcc. Check it out, might save you some time and headaches for $55. Worth checking out anyway.