CCS/TM4C1294NCPDT: Creating custom Report ID's for USB HID report descriptor

Alexander Jatsiv

Part Number: TM4C1294NCPDT

Tool/software: Code Composer Studio

For clarification I am basing my code off of the example in the TivaWare library called usb_dev_keyboard, from which they connected a keyboard to their tiva device. This was modified and it works with a vendor usage page and connects to a PC as the host.

I am currently trying to create a specific HID vendor usage page to connect my controller to my PC. Connection between the two is fine, however whenever I want to specify different Report ID's, the send and receive functionality of the code does not work at all. If I do not specify any Report ID (or just comment it out of the report descriptor) it works completely fine. I am wondering if something is wrong in my report description or in any other description. Or is this a problem with the base layer of code that did not support multiple report ids with the usb_dev_keyboard example.

Below is the code that I am working with:

7853.usb_dev_keyboard.zip

over 5 years ago

0 Charles Tsai over 5 years ago

TI__Guru**** 191906 points

Hi,

I'm not an USB expert in general and neither in the HID report descriptor so I'm not sure how much I can help here. I do a comparison between your custom report descriptor with the default provided by the TivaWare and see quite some differences. If you intent to create your own custom report descriptor I will suggest you do so perhaps one or few entries in the descriptor at a time instead of drastic change. I also found a few links with examples on how to create HID keyboard report descriptor. Hopefully they will provide some guidance. Please share with the community what you find that may benefit people who are looking for the same solution.

https://www.ti.com/lit/an/slaa514/slaa514.pdf?ts=1594928301422&ref_url=https%253A%252F%252Fwww.google.com%252F

https://www.silabs.com/documents/public/application-notes/AN249.pdf

0 Alexander Jatsiv over 5 years ago in reply to Charles Tsai

Prodigy 30 points

Hi Charles,

Thank you for your feedback, however the report descriptor on the left, as you have shown, does work (which is the one from my code). It is only when I uncomment out the Report IDs is where the issue lies. Its seems like the sending and receiving functionality of the code stops working when I try to implement Report IDs.

The differences in the two descriptors should not matter since we are telling the Host the report that is being sent will look like. And I believe that the descriptor is written correctly as well. Any updates that I have I will surely update this thread with.

Thanks,

Alex

0 Charles Tsai over 5 years ago in reply to Alexander Jatsiv

TI__Guru**** 191906 points

Hi Alex,

Thank you for trying to investigate and share with us your finding. I found this article that talks about Report ID. Please go through it and perhaps you can do some searching on your own too for Report ID. I'm not sure if you really need Report ID in your descriptor if you only have one report to send to the host. In another word, you will use Report ID to distinguish between reports if you have multiple reports. Perhaps my interpretation is wrong but I hope this article will help you anyway.

http://who-t.blogspot.com/2018/12/understanding-hid-report-descriptors.html

0 Charles Tsai over 5 years ago in reply to Charles Tsai

TI__Guru**** 191906 points

I found another post with similar issue as yours. Although it is for a different device, but I think the solution should be independent. Try it and see if resolves your issue.

https://www.microchip.com/forums/m1001939.aspx

0 Alexander Jatsiv over 5 years ago in reply to Charles Tsai

Prodigy 30 points

Hi Charles,

Thank you for your last post. I have finally fixed the problem. I was sending a report from the PC to the microcontroller and saw that once I declared a report ID on the device side of things, the total length of the Packet became 65 bytes. The code was meant only to look for 64 bytes when any amount of data was received which was is why I keep getting an error code back. Now that I accounted for it for both the receive and send functions, everything works perfectly fine now.

Thanks,

Alex

0 Charles Tsai over 5 years ago in reply to Alexander Jatsiv

TI__Guru**** 191906 points

Glad your problem is resolved.

0 Andy Peters over 5 years ago in reply to Charles Tsai

Genius 3945 points

Charles Tsai said:

I found another post with similar issue as yours. Although it is for a different device, but I think the solution should be independent. Try it and see if resolves your issue.

https://www.microchip.com/forums/m1001939.aspx

Just a note about Report IDs. Many moons ago I did a TAS1020B-based USB Audio product. The product didn't have any front-panel controls at all, so all gain and other settings had to be sent from the computer. I used an HID interface in the product (in addition to the Audio Streaming and Audio Control interface) for messages which set channel gain, enabled phantom power, and also provided a firmware-update feature. (DFU requires a custom class and worse, a custom host driver.) The HID interface took advantage of the Report ID to differentiate between the feature controls.

The Report ID is a very handy feature of the HID class!

0 Charles Tsai over 5 years ago in reply to Andy Peters

TI__Guru**** 191906 points

Hi Andy,

Thanks for your inputs. Looks like you have a lot of USB experiences that we can ping you for advises in the future. :-)

0 Andy Peters over 5 years ago in reply to Charles Tsai

Genius 3945 points

Charles Tsai said:

Hi Andy,

Thanks for your inputs. Looks like you have a lot of USB experiences that we can ping you for advises in the future. :-)

Glad to help. And once I sort out the Tiva USB library I'll be even more helpful. I may also be very aggravated ...

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Arm-based microcontrollers forum

CCS/TM4C1294NCPDT: Creating custom Report ID's for USB HID report descriptor