USBX CustomHID OUT Report size issue

[nicco]

USB HID Endpoint Size Challenge - My Experience

Issue Description

I'm experiencing an issue with USB HID endpoint sizes in my firmware running on an STM32U5 microcontroller with ThreadX RTOS and USBX middleware. Specifically:

1. My host is sending 20-byte messages (1 byte report ID + 1 byte page number + 18 bytes of data)
2. I've tried setting the endpoint maximum packet size (USBD_HID_CUSTOM_EPOUT_HS_MPS and USBD_HID_CUSTOM_EPOUT_FS_MPS) to 24U and 32U, but neither worked
3. Only a 16-byte endpoint size works with my hardware, which creates a mismatch with my 20-byte report size
4. Most importantly, my USBD_Custom_HID_SetReport callback function does not get called at all when using 24U or 32U endpoint sizes

Technical Details

• Hardware Platform: STM32U5 series microcontroller
• RTOS: ThreadX
• USB Stack: USBX middleware
• USB Class: Device HID Custom Class
• Report Size: 20 bytes (defined in HID report descriptor)
• Working Endpoint Size: 16 bytes
• Non-working Endpoint Sizes: 24, 32, 64 bytes
• Thread Stack Size: 2048 bytes
• Memory Usage: ~70% of available RAM

Attempted Solutions

1. I initially tried setting the endpoint size to match the report size (24U)
2. I tried increasing the endpoint size to 32U and 64U (power of 2)
3. I modified USBD_Custom_HID_EventMaxLength to return 16U instead of 20U to match the working endpoint size but I'm loosing 4 bytes
4. I've tried to increase memory, thread size and bits alignment

My Questions

1. Why don't 24-byte or 32-byte endpoint sizes work with the STM32U5 USB controller when using USBX?
2. Why does USBD_Custom_HID_SetReport not get called when using 24U or 32U endpoint sizes?
3. Is there a hardware limitation or configuration issue that restricts the endpoint size to 16 bytes?
4. Are there specific alignment requirements for USB endpoint sizes on STM32U5 that aren't documented?
5. Could this be a bug in the USBX implementation for STM32U5?
6. Are there any specific USB controller registers or configurations that need to be adjusted to support larger endpoint sizes?
7. Is there a memory allocation or thread stack size issue that could be affecting larger endpoint sizes?

CUBEMx Project Settings for USBX

USBX.BSP.number=1
USBX.Core_System=1
USBX.IPParameters=Core_System,UX_Device_CoreStack,UX_Device_Controller,UX_SLAVE_REQUEST_DATA_MAX_LENGTH,USBD_PID,USBD_PRODUCT_STRING,USBD_SERIAL_NUMBER,UX_DEVICE_APP_MEM_POOL_SIZE,USBD_COMPOSITE_USE_IAD,USBX_DEVICE_SYS_SIZE,MAX_POWER_IN_MILLI_AMPER,UX_DEVICE_HID_CORE,USBD_MANUFACTURER_STRING,REG_USBX_DEVICE_CON_CK,UX_DEVICE_HID_CUSTOM,USBD_HID_CUSTOM_EPIN_FS_MPS,USBD_HID_CUSTOM_EPIN_HS_MPS,USBD_VID,UX_THREAD_PRIORITY_DCD,UX_DEVICE_CLASS_HID_INTERRUPT_OUT_SUPPORT,USBD_HID_CUSTOM_EPOUT_ADDR,USBD_HID_CUSTOM_EPOUT_FS_MPS,USBD_HID_CUSTOM_EPOUT_HS_MPS
USBX.MAX_POWER_IN_MILLI_AMPER=500
USBX.REG_USBX_DEVICE_CON_CK=1
USBX.USBD_COMPOSITE_USE_IAD=1
USBX.USBD_HID_CUSTOM_EPIN_FS_MPS=64
USBX.USBD_HID_CUSTOM_EPIN_HS_MPS=64
USBX.USBD_HID_CUSTOM_EPOUT_ADDR=2
USBX.USBD_HID_CUSTOM_EPOUT_FS_MPS=16
USBX.USBD_HID_CUSTOM_EPOUT_HS_MPS=16
USBX.USBD_MANUFACTURER_STRING=XXX
USBX.USBD_PID=XXX
USBX.USBD_PRODUCT_STRING=XXX
USBX.USBD_SERIAL_NUMBER=XXX
USBX.USBD_VID=XXX
USBX.USBX_DEVICE_SYS_SIZE=8*1024
USBX.UX_DEVICE_APP_MEM_POOL_SIZE=11*1024
USBX.UX_DEVICE_CLASS_HID_INTERRUPT_OUT_SUPPORT=1
USBX.UX_DEVICE_HID_CORE=1
USBX.UX_DEVICE_HID_CUSTOM=1
USBX.UX_Device_Controller=1
USBX.UX_Device_CoreStack=1
USBX.UX_SLAVE_REQUEST_DATA_MAX_LENGTH=64
USBX.UX_THREAD_PRIORITY_DCD=20
USBX0.BSP.STBoard=false
USBX0.BSP.api=Unknown
USBX0.BSP.component=
USBX0.BSP.condition=SEMAOoUSBOoDRDOoFSOoDEVICEOoFOROoUSBX & DIE455
USBX0.BSP.instance=USB_DRD_FS
USBX0.BSP.ip=USB_DRD_FS
USBX0.BSP.mode=Device_Only_FS
USBX0.BSP.name=USB_Device
USBX0.BSP.semaphore=
USBX0.BSP.solution=USB_DRD_FS


Thanks!