Windows and HID Device questions

[jhinkle]

In the past, I used an FTDI device to provide a USB to controller (via a uart) to pass data back and forth.

I finally decided to understand USB and use the internal microcontroller's USB component.

After reading Jan's Second and Fifth USB editions, and others - I was left with the assumption that a HID class device (using my own defined report structures) would be easy.

Question 1:  If attempting to use a Windows provided HID driver - can the endpoint support 64 byte transfers or are they limited to 8?

I am developing on a STM32F103 device.  I have developed the device side code and it successfully enumerates.  I'm using a Beagle USB 12 tool to analyze the USB packets.

I wrote a test C++ application to communicate with the HID device but found windows failed to open the device.  Looking in "Device Manager", I found my HID device - it showed it enumerated properly but the third event stated "was not migrated due to partial or ambiguous match" - so I suspect a driver related issue.

Question 2:  I plan on having only my custom Win10 Application communicate with my device (not commercial - just a personal hobby project) - Which device class would be best/easiest to implement - HID - or a CDC (virtual com port)?

Depending on any reply to my questions above - I will ask more questions.  Thanks in advance for any reply/insight.

 

[Jan Axelson]

Only low speed is limited to 8 byte packets.

For a custom HID you would need to use API calls or a third party tool. For CDC you can use. NET SerialPort class or similar. If the ftdi interface works for your project, nothing wrong with continuing to use it.

[jhinkle]

Thanks Jan.  All the microcontrollers I use have a USB cell onboard but I have never used it.  The FTDI prices are going up and availability going down.  Just from a knowledge base, I want to get a total USB communication going and understand the complete implementation.  I spent today converting the USB device from HID to CDC.  I just need to test enumeration and host communication. 

I a very old fart and have never cared for C#.  All my embedded work is in assembler and C with the PC tools developed in C++.

Thanks for your reply.

[bpaddock]

If you've not already found it HDIPAI from the libusb project will be helpful for you, for the PC end.

https://github.com/libusb/hidapi