Will USB communication in Windows 10 be done in Bulk mode?
I'm in the process of selecting a PC and would like to know how to transfer Windows 10 to other devices for USB communication.
There are four transfer methods for USB communication, Control, Interrupt, Bulk, and Isochronous, and which one is used depends on the host.
I'm hoping to use the Bulk method of communication because I don't want USB communication without retransmission.
Thank you!
and which one is used depends on the host
Yes and no. The host must use the method appropriate for a device, and the device has endpoint descriptors which define whether an endpoint is bulk,interrupt or isochronous.
Note that common devices have specific endpoint type requirements: Mass storage use bulk while HID devices (e.g. mice or keyboards) use interrupt ep.
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I am trying to talk to a MSC USB device (interface class 8, subclass 6, protocol 0x50) via a plain USB API with endpoints (all set up for me).
Provided I have a valid CDB, such as for "Test Unit Ready", how to I send that over the USB interface?
Where can I find examples or docs for how this is done?
Background: The actual platform is macOS, which doesn't provide SCSI-passthrough for block devices, and the native SCSI API is also not available in this case.
I have, however, been able to initiate communication on the USB level with the device, and am now trying to circumvent the blocked SCSI device level access by talking thru USB directly.
Most such devices implement the so-called “Bulk Only” protocol, which is specified here: https://usb.org/document-library/mass-storage-bulk-only-10
Essentially, you send a 31-byte “Command Block Wrapper”, which includes the CDB and is specified in section 5.1 of the spec, to the device via the bulk out endpoint. You then read or write the data to be transferred from the input bulk endpoint or to the output bulk endpoint and finally read the 13-byte command status wrapper from the bulk in pipe.
However, note that you’ll need to make sure the OS hasn’t already loaded a driver for the device - from user space, the system won’t give you access to the endpoints when a kernel driver has claimed them anyway, but if you were to attempt to use the same pipes as the default driver from a kext, you’d get unpredictable results.
I am looking at implementing USB communication on a MCU which has a USB engine built into it. Basically you have access to the pipes/endpoints.
I am a little bit confused on the USB stack now. It appears that drivers operate on another level above the pipe/endpoint setup, so the pipe/endpoint is like a middle level layer that drivers are built on. Is this correct?
Secondly, I am interested in simulating serial communication over USB. It appears windows has a premade driver so on the computer side I do not need to program the pipe level.
How do I find out what I need to implement on the MCU to make it behave correctly with the generic serial driver?
This is an answer to your second question regarding the serial communication.
The USB standard defines a communication device class (CDC) for serial communication. The required drivers on the host side are implemented by Windows, macOS, Linux and many more operation systems.
The relevant CDC subclass is PSTN. The relevant documents are found in Class definition for Communication Devices 1.2.
The device basically implements four endpoints:
Control endpoint for configuration requests (baud rate, DTR state etc.). Have a look at SetLineCodeing, GetLineCoding and SetControlLineState.
Bulk endpoint for USB to serial transmission
Bulk endpoint for serial to USB transmission
Interrupt endpoint for notifications (DCD state, errors). See SerialState.
And of course you need to get the device descriptor right.
On top of that, you need to implement all the standard USB requests.
Chances are high that this has already been written for your MCU, both the standard requests and the serial communication. So why not use the existing code?
I'm looking to write a simple Windows driver to enable running TCP/IP over a proprietary RF module. The module already provides Ethernet-style data packets with source/destination MAC, so I just need to layer IP packets (generated by the regular Microsoft IPv4 subsystem), set the MTU appropriately so they will be the right size, and then call the module's serial API. I'll need to be able to handle transmit statuses and implement an ARP protocol as well. I want the driver to expose a new interface similar to a wifi or ethernet card in Network Connections and use the normal Windows IP stack.
The module is UART and might be connected via FTDI chip, RS-232 converter, or native UART on an IoT Core board, so it will just be talking to a generic serial port. I am fine with only running on Windows 10, but I'm still not sure what to use. Can I use the UWP VPN provider? Do I need to write an NDIS miniport driver, or an interface provider? Also, how will I handle the driver needing complete control over the serial port at all times? I can't write a serial driver as it might be connected via many different types of serial ports.
First allow me to say that I don't have any experience developing drivers for OSX, nor drivers for Windows. So, there are a lot of things that I don't understand about how drivers work; I'm sure it'll be evident in my question.
I have a modem that is able to open and close TCP/UDP sockets using AT commands. I would like to create some kind of program (kernel extension? driver?) that implements a network driver, converting the network interface calls into AT command serial messages.
That's the basic jist of it. I'm essentially asking if anybody can point me in the right direction / give me a high level overview of how they would approach it and what Apple guides to focus on.
The XNU networking stack -- like most network stacks -- expects network devices to send and receive IP packets directly. It isn't tooled to work with network devices that handle part of the network stack (like TCP or UDP) internally -- it won't be possible to implement a network driver which uses this device.
You might have more luck exposing this device as a SOCKS proxy. You will need to write a userspace daemon which listens on a TCP port on localhost (on the computer) and relays traffic to the serial device; once that's done, you can set the computer to use that device as a SOCKS proxy in the Networking control panel.
(As an aside: most devices that implement this type of interface have a very low limit on the number of open sockets -- often fewer than 10. They're unlikely to be able to handle the network load generated by a desktop OS.)
I am modifying a monitor controller for a prototype. It would be convenient to send commands to the prototype using DDC/CI. In Windows, I can't find an obvious way to send a DDC/CI command to a "display dependent device".
The Monitor Configuration API can send virtual control panel commands, but it does not give access to display dependent devices (which would have an I2C address other than 0x6e).
Nicomsoft's WinI2C/DDC product seems to give access to a display dependent device, but it is end-of-life. I would prefer not to build a dependency on an end-of-life product.
NVIDIA's NVAPI has an I2C API, but I would like a solution that also works with Intel and AMD graphics adaptors.
A solution exists for windows which respect XDDM driver display model. Windows 8 and 10 use WDDM.
In XDDM there is a windows O.S. supplied video port driver, and the hardware vendor supplies a miniport driver. When the miniport driver call's the video port driver's edid helper api (VideoPortDDCMonitorHelper), the miniport must supply 4 i2c function pointers as arguments.
In order to utilize these interfaces however you must be acting as the video port driver. So you have to write a video port lower filter driver which just passes along all the interfaces on from the windows supplied video port driver to the miniport driver. Hook the api's and export them to a usermode driver or ioctl which an application can call.
It may be possible to simply mount an instance of the miniport driver and some how get it to call VideoPortDDCMonitorHelper. But with out the help of the actual video port driver it would be difficult to get guidance on how to do that. Also you would have 2 instances of the driver running which may be against the rules for windows.
It does not appear this solution works for windows 8 and 10 because they use a different display driver model which doesn't appear to expose low level control of i2c. It is internal to the miniport driver.