C++ USB Programming

Question

I am new to hardware programming(especially USB) so please bear with me and my questions. I am using C++ and I need to send/receive some data (a byte array) to/from a USB port on a microprocessor board.

Now, I have done some serial port programming before and I know that for a serial port you have to open a port, setup, perform i/o and finally close the port. I am guessing to use a USB port, it is not as simple as what I mentioned above.

I do know that I want to use Microsoft standard drivers and implement standard Windows IO commands to accomplish this, since I believe there are no drivers for the microprocessor board for me to interact with.

If somebody can point me in the right direction as to the steps needed to "talk" to a USB port (open, setup, i/o) via standard Windows IO commands, I would truly and greatly appreciate it. Thanks you so much!!

Answer 1

USB in a nutshell is excellent background reading.

For a generic USB module try LibUSB which includes some examples of talking to standard devices. LibUSB-Win32 is the windows port of that library.

You're right though, it's nowhere near as simple as an RS232 port.

What microprocessor are you using? Does it come with any USB hardware or are you thinking of trying to implement it all in software (not something I'd recommend even contemplating!). A lot of microprocessors come with code samples which can emulate simple HID USB devices like keyboards / mice etc. which you can use as a starting point. Failing that, there's probably a few off-the-shelf options which will save you a lot of headaches :-)

Answer 2

Find out the USB chipset used on the microprocessor board, e.g. Ftdi, Cypress, etc. These manufacturers supply drivers, libraries and example programs for the comms, this is the easiest way.

There are no 'standard' drivers as such unless your board is set up as an HID device, however if you are using Windows, Microsoft supply a WinUSB.sys 'generic' driver which may or may not meet your needs (it doesn't support Isochronous transfers).

Answer 3

Should you write a driver for the USB device that will attach itself. If you know the type of chip that has the USB i/o on the board, the driver will be for that device.

There may already be driver's for that chip if it is an STM or there may be an API to help develop drivers for it. It would probably be a custom device but you should look through device types to see if there is an existing type that matches your device. If so there may also be a driver already for it which you can use. Information about the board is necessary.

WRITE YOUR OWN DRIVER With out getting too far into it, you should learn Microsoft's driver model, the difference between user mode and kernal mode drivers, what driver node's represent, driver hierarchy and how they logically attach themselves, different types of drivers (filter, function, bus), how kernal driver's communicate with user interface, dynamic link libraries, frameworks and API's, WDM framework/API, KMDF and UMDF API's and this is just a short list.

OR you can use an existing driver.

USE USB MICROCONTROLLER SUPPLIED DRIVER We do not know what firmware the USB microcontroller is using, if any. If there is no firmware (if say the chip came with out it or relies on eprom to store it and not flash) then if we knew if the chip supports usb bootloader, you can flash it or load it's firmware through the USB and there is no need for JTAG or other peripherials. Likely the usb alone is capable of getting you off the ground and anywhere from there. Typically these types of questions arise when considering board's with out a USB microcontroller.

Here is a link to a slighly related driver. Most USB microcontrollers serve the purpose of switching USB communication to UART as most microconrollers that actually do the thinking and control everything are not equiped with USB i/o but instead UART or some other i/o pins like I2C or SPI etc..

https://www.silabs.com/products/mcu/Pages/USBXpress.aspx

That driver may actually work, if not something similar but for the manufacturer of your USB microcontroller; will almost certainly do the job. Hope this helps.

Answer 4

By hardware programming, do you mean you will be programming the microcontroller? If so, there is no way you will use "standard windows drivers" or anything like that.

The USB standard is very thick. Check it out here

It is a very involved topic and I recommend finding USB implementations already created for your microcontroller. (which we may be able to find if you gave us more info)