Hi all,
I would like to consult a technical issue here. I am trying to develop a simple USB HID communication between PC and device board with STM32F400. On the host side (PC) I am using Visual Studio to build my application using a DLL for USB HID. The communication works fine but only for reports until 255 bytes long. When I try to set higher output report value (e.g. 1023 bytes) in uVision I can still recieve only reports 255 bytes long. I debugged this with ULINK2 and examined the "usbd_hid_set_report" function. The parameter len is still 255 even though USBD_HID_OUTREPORT_MAX_SZ is set to 1023 and the array sent from PC has 1023 bytes. I can also check this value on the PC side by reading the descriptor and the value reported by the USB device (STM32F400) is still 255 bytes even though it should be 1023 bytes. Do you have any idea where I am going wrong? Max allowed value for USBD_HID_OUTREPORT_MAX_SZ is 65535 bytes according to the documentation.
Any ideas?
Best regards, Steven.
> I can also check this value on the PC side by reading the descriptor and the value reported by the USB device (STM32F400) is still 255 bytes even though it should be 1023 bytes.
Your finding suggests a problem on the report descriptor definition.
You are talking about RL-USB library In this library, the HID report descriptor is defined in usb_lib.c
C:\Keil\ARM\RV31\INC\usb_lib.c __weak \ const U8 USBD_HID_ReportDescriptor[] = { HID_UsagePageVendor( 0x00 ), HID_Usage ( 0x01 ), HID_Collection ( HID_Application ), HID_LogicalMin ( 0 ), /* value range: 0 - 0xFF */ HID_LogicalMaxS ( 0xFF ), HID_ReportSize ( 8 ), /* 8 bits */ HID_ReportCount ( USBD_HID_INREPORT_MAX_SZ ), HID_Usage ( 0x01 ), HID_Input ( HID_Data | HID_Variable | HID_Absolute ), HID_ReportCount ( USBD_HID_OUTREPORT_MAX_SZ ), // <------- HID_Usage ( 0x01 ), HID_Output ( HID_Data | HID_Variable | HID_Absolute ), HID_ReportCount ( USBD_HID_FEATREPORT_MAX_SZ), HID_Usage ( 0x01 ), HID_Feature ( HID_Data | HID_Variable | HID_Absolute ), HID_EndCollection, };
The source of your problem lies in HID_ReportCount() macro It is defined in C:\Keil\ARM\RL\USB\INC\usb_hid.h
#define HID_ReportCount(x) 0x95,x
This macro accepts no more than 255 bytes.
You may override above definition by having this code on your file.
#define HID_ReportCountS(x) 0x96, 0x00FF & (x), (0xFF00 & (x)) >> 16 const U8 USBD_HID_ReportDescriptor[] = { HID_UsagePageVendor( 0x00 ), HID_Usage ( 0x01 ), HID_Collection ( HID_Application ), HID_LogicalMin ( 0 ), /* value range: 0 - 0xFF */ HID_LogicalMaxS ( 0xFF ), HID_ReportSize ( 8 ), /* 8 bits */ HID_ReportCount ( USBD_HID_INREPORT_MAX_SZ ), HID_Usage ( 0x01 ), HID_Input ( HID_Data | HID_Variable | HID_Absolute ), #if USBD_HID_OUTREPORT_MAX_SZ < 0xFF HID_ReportCount ( USBD_HID_OUTREPORT_MAX_SZ ), #else HID_ReportCountS ( USBD_HID_OUTREPORT_MAX_SZ ), #endif HID_Usage ( 0x01 ), HID_Output ( HID_Data | HID_Variable | HID_Absolute ), HID_ReportCount ( USBD_HID_FEATREPORT_MAX_SZ), HID_Usage ( 0x01 ), HID_Feature ( HID_Data | HID_Variable | HID_Absolute ), HID_EndCollection, };
Tsuneo
Umm... A couple of bugs on above snippet. I may post it too quick, before examining the code again ;-)
#define HID_ReportCountS(x) 0x96, 0x00FF & (x), (0xFF00 & (x)) >> 8 // <--- const U8 USBD_HID_ReportDescriptor[] = { HID_UsagePageVendor( 0x00 ), HID_Usage ( 0x01 ), HID_Collection ( HID_Application ), HID_LogicalMin ( 0 ), /* value range: 0 - 0xFF */ HID_LogicalMaxS ( 0xFF ), HID_ReportSize ( 8 ), /* 8 bits */ HID_ReportCount ( USBD_HID_INREPORT_MAX_SZ ), HID_Usage ( 0x01 ), HID_Input ( HID_Data | HID_Variable | HID_Absolute ), #if USBD_HID_OUTREPORT_MAX_SZ <= 0xFF // <--- HID_ReportCount ( USBD_HID_OUTREPORT_MAX_SZ ), #else HID_ReportCountS ( USBD_HID_OUTREPORT_MAX_SZ ), #endif HID_Usage ( 0x01 ), HID_Output ( HID_Data | HID_Variable | HID_Absolute ), HID_ReportCount ( USBD_HID_FEATREPORT_MAX_SZ), HID_Usage ( 0x01 ), HID_Feature ( HID_Data | HID_Variable | HID_Absolute ), HID_EndCollection, };
Hi Tsuneo,
some development since my post. Before I saw your reply I tried downloading latest uVision. Looks like their programmers found the issue before me. In version 4.60 the bug is corrected in the way you outlined. They only wrote the code in slightly different way but the functionality is the same. You can check their version below.
#define HID_ReportCountS(x) 0x96,(x&0xFF),((x>>8)&0xFF) #if (USBD_HID_OUTREPORT_MAX_SZ > 255) HID_ReportCountS ( USBD_HID_OUTREPORT_MAX_SZ ), #else HID_ReportCount ( USBD_HID_OUTREPORT_MAX_SZ ), #endif
However this is still not a perfect solution. For some reason this works only until 8192 bytes. Then it starts from 0 again. So for example 16384 bytes long report is shown on PC side as 8192 bytes long and also if you try to send reports 16384 bytes long back to the board only 8192 bytes are received.
Get more clues on the bug. When USBD_HID_OUTREPORT_MAX_SZ is set to 16384, 1) Does the report descriptor, read out by the sniffer, define correct value? 2) Do you send the output report over the interrupt OUT endpoint, or Set_Report request?
1) No. If for example HID_OUTREPORT_MAX_SZ is set to 9000 the sniffer reads out 808. In other words it looks as if the value was bitwise masked with logical and by 0x1FFF. This applies for all the values up to 65535 so you are going to read out 808 if you set HID_OUTREPORT_MAX_SZ to 17192 as well. 2) Interrupt OUT endpoint.
I ran this example of MDK v4.60 on my STM32F4 Discovery board. C:\Keil\ARM\Boards\Keil\MCBSTM32F400\RL\USB\Device\HID
Surely, as you said, this version has revised above report descriptor problem. I saw the exact number on the report descriptor, same as USBD_HID_OUTREPORT_MAX_SZ, using a hardware bus analyzer.
Also, I saw 808 bytes transfer on the interrupt OUT endpoint, when Keil's HID_Client PC application. C:\Keil\ARM\Utilities\HID_Client
Debugging on this PC application has revealed, HidP_GetCaps() returns 809 (808 + 1: report ID) at OutputReportByteLength field, whereas the report descriptor sets it to 9000.
HID.cpp int HID_FindDevices() { ... /* Get Preparsed Data */ ok = HidD_GetPreparsedData(DevHandle, &PreparsedData); if (!ok) continue; /* Get Device's Capabilities */ HidP_GetCaps(PreparsedData, &Capabilities); /* Free the PreparsedData */ HidD_FreePreparsedData(PreparsedData); /* Remember Device Interface Detail Data for acceptable Devices */ if ((Capabilities.UsagePage == 0xFF00) && (Capabilities.Usage == 0x0001)) { DevDetailData[DevCount] = DevDetail; DevDetailDataSz[DevCount] = Sz; DevInputReportSz[DevCount] = Capabilities.InputReportByteLength; DevOutputReportSz[DevCount] = Capabilities.OutputReportByteLength; // <-----
I have an impression that MS does nasty coding, but further investigation is required. Today, my free time has been expired. I'll report it later.
Ah, for temporary workaround, hard-code USBD_HID_OUTREPORT_MAX_SZ value on the above line, instead of OutputReportByteLength.
DevOutputReportSz[DevCount] = 9000; // Capabilities.OutputReportByteLength;
If it is MS related then it is an issue. I tried the hardcoding approach and it works only to a certain extent. I am using an USB HID component for Visual Studio available here: www.codeproject.com/.../usb_hid.zip. I can do changes in the source files and recompile the DLL. So I did what you suggested and this way I could influence the output report length on the PC side. However when I try having this value larger than 8192 and send data to the evaluation board the code does not jump to the interrupt routine, i.e. data is not recieved. For values below 8192 everything works fine, interrupt routine is invoked and data recieved.
Steven.
The HID stock driver of XP has this 8K bytes report size limitation. Maybe it's "feature" of MS HID implementation.
I don't yet test this issue on Windows 7 and 8. For these days, I've been working on another place, far from my lab. I can't reach to test resources, on this weekend, too. I hope I could confirm it on these OS versions at next weekend.