Small question about HID USB device

Hi
Thanks for reply.

I'm using USB HID sample that is distributed with RealView as my base code.

I will try to find out how I should split my report for sending in wMaxPacketSize buffers.
But a questions:
1- Using bigger wMaxPacketSize(up to 64) will increase performance,isn't it?
2- When my device is going to send and receive data is it possible to use EP0 for sending control and data to host and another endpoint for receiving data from host(2 endpoints) or I should use EP0 as control and 2 other endpoint for sending or receiving data(3 endpoints used). if both possible,which one is better?

Regards

Hi
Thanks for reply.

I'm using USB HID sample that is distributed with RealView as my base code.

I will try to find out how I should split my report for sending in wMaxPacketSize buffers.
But a questions:
1- Using bigger wMaxPacketSize(up to 64) will increase performance,isn't it?
2- When my device is going to send and receive data is it possible to use EP0 for sending control and data to host and another endpoint for receiving data from host(2 endpoints) or I should use EP0 as control and 2 other endpoint for sending or receiving data(3 endpoints used). if both possible,which one is better?

Regards

Hi
Thanks for reply.

That post was really useful,thanks a lot... :)

Even though my HID device is working on a request/response nature that starts from host, I think it is possible to use only 2 endpoints(EP0 for control and another one for data transfer), but I think that I can reach better performance using 3 endpoints(EP0 and 2 more,1 for sending and another one for receiving data) too.

I have made changes to HID library for this reason, but I have an strange problem and I think it comes from my descriptors, but I cannot find that problem.

I'm observing USB ports using USBlyzer. When I attach my programmed USB device to PC, it immediately says "Unrecognized USB device" and I cannot see any logs in USBlyzer. But when I start debugging my device by ULINK debugger and set a breakpoint in USB_EndPoint0, I see it breaks several times for getting various descriptors. This will not help recognizing device, but this time I can see USB requests in USBlyzer and some steps of USB configuration proceeds. From my point of view, delay that happens by breaking on my breakpoint in USB_EndPoint0, is the reason that some steps of configuration proceeds.
I thought that this problem happens because my USB_ReadEP and USB_WriteEP is not interrupt protected. then I used SWI 0 and 1(because I don't use RTX, then using them should not be any problem) to protect these 2 functions. But it did not solve problem.
Any idea why this happens?
This is list of my descriptors:

/* HID Report Descriptor */
const BYTE HID_ReportDescriptor[] = {
  HID_UsagePageVendor(0x00),
  HID_Usage(0x01),
  HID_Collection(HID_Application),
    HID_UsagePage(0x01),
    HID_LogicalMin(0),
    HID_LogicalMax(0xFF),
    HID_ReportCount(64),
    HID_ReportSize(8),
    HID_Input(HID_Data | HID_ARRAY | HID_Absolute),
    HID_UsagePage(0x02),
    HID_LogicalMin(0),
    HID_LogicalMax(0xFF),
    HID_ReportCount(64),
    HID_ReportSize(8),
    HID_Output(HID_Data | HID_ARRAY | HID_Absolute),
  HID_EndCollection,
};
/* USB Configuration Descriptor */
/*   All Descriptors (Configuration, Interface, Endpoint, Class, Vendor */
const BYTE USB_ConfigDescriptor[] = {
/* Configuration 1 */
  USB_CONFIGUARTION_DESC_SIZE,       /* bLength */
  USB_CONFIGURATION_DESCRIPTOR_TYPE, /* bDescriptorType */
  WBVAL(                             /* wTotalLength */
    USB_CONFIGUARTION_DESC_SIZE +
    USB_INTERFACE_DESC_SIZE     +
    HID_DESC_SIZE               +
    USB_ENDPOINT_DESC_SIZE * 2
  ),
  0x01,                              /* bNumInterfaces */
  0x01,                              /* bConfigurationValue */
  0x00,                              /* iConfiguration */
  USB_CONFIG_BUS_POWERED /*|*/       /* bmAttributes */
/*USB_CONFIG_REMOTE_WAKEUP*/,
  USB_CONFIG_POWER_MA(100),          /* bMaxPower */
/* Interface 0, Alternate Setting 0, HID Class */
  USB_INTERFACE_DESC_SIZE,           /* bLength */
  USB_INTERFACE_DESCRIPTOR_TYPE,     /* bDescriptorType */
  0x00,                              /* bInterfaceNumber */
  0x00,                              /* bAlternateSetting */
  0x02,                              /* bNumEndpoints */
  USB_DEVICE_CLASS_HUMAN_INTERFACE,  /* bInterfaceClass */
  HID_SUBCLASS_NONE,                 /* bInterfaceSubClass */
  HID_PROTOCOL_NONE,                 /* bInterfaceProtocol */
  0x5C,                              /* iInterface */
/* HID Class Descriptor */
/* HID_DESC_OFFSET = 0x0012 */
  HID_DESC_SIZE,                     /* bLength */
  HID_HID_DESCRIPTOR_TYPE,           /* bDescriptorType */
  WBVAL(0x0100), /* 1.00 */          /* bcdHID */
  0x00,                              /* bCountryCode */
  0x01,                              /* bNumDescriptors */
  HID_REPORT_DESCRIPTOR_TYPE,        /* bDescriptorType */
  WBVAL(HID_REPORT_DESC_SIZE),       /* wDescriptorLength */
/* Endpoint, HID Interrupt In */
  USB_ENDPOINT_DESC_SIZE,            /* bLength */
  USB_ENDPOINT_DESCRIPTOR_TYPE,      /* bDescriptorType */
  USB_ENDPOINT_IN(1),                /* bEndpointAddress */
  USB_ENDPOINT_TYPE_INTERRUPT,       /* bmAttributes */
  WBVAL(0x0040),                     /* wMaxPacketSize */
  0x20,          /* 32ms */          /* bInterval */
/* Endpoint, HID Interrupt Out */
  USB_ENDPOINT_DESC_SIZE,            /* bLength */
  USB_ENDPOINT_DESCRIPTOR_TYPE,      /* bDescriptorType */
  USB_ENDPOINT_OUT(2),                /* bEndpointAddress */
  USB_ENDPOINT_TYPE_INTERRUPT,       /* bmAttributes */
  WBVAL(0x0004),                     /* wMaxPacketSize */
  0x20,          /* 32ms */          /* bInterval */
/* Terminator */
  0                                  /* bLength */
};

As you see my Report count is currently 64, so it should be transferable in 1 USB transaction,because I have configured wMaxPacketSize to 64, But I need to increase it to 128 later.
In addition there are 2 more questions too:
1- what is bAlternateSetting for?
2- when I were checking USB library code, I saw this function:

void USB_DataInStage (void) {
  DWORD cnt;

  if (EP0Data.Count > USB_MAX_PACKET0) {
    cnt = USB_MAX_PACKET0;
  } else {
    cnt = EP0Data.Count;
  }
  cnt = USB_WriteEP(0x80, EP0Data.pData, cnt);
  EP0Data.pData += cnt;
  EP0Data.Count -= cnt;
}

But this function was somehow strange, because if EP0Data.Count is more than USB_MAX_PACKET0, then how the reminder of buffer will be transfered? I thought it should be something like this:

void USB_DataInStage (void) {
  DWORD cnt;

  while (EP0Data.Count)
  {
    if (EP0Data.Count > USB_MAX_PACKET0) {
      cnt = USB_MAX_PACKET0;
    } else {
      cnt = EP0Data.Count;
    }
    cnt = USB_WriteEP(0x80, EP0Data.pData, cnt);
    EP0Data.pData += cnt;
    EP0Data.Count -= cnt;
  }
}

isn't it?

Regards

> Even though my HID device is working on a request/response nature that starts from host,…

Send request from PC application to the interrupt OUT endpoint.
Parse the request, and send back response to the interrupt IN endpoint.



> When I attach my programmed USB device to PC, it immediately says "Unrecognized USB device" and I cannot see any logs in USBlyzer.

Maybe, on your board, D+ pull-up resistor is fixed one, not controlled by the MCU.
Which board are you using?
Is it a development board or custom one?
Can you show us its schematics?



Report descriptor is revised as follows.
Configuration descriptor set is fine.

/* HID Report Descriptor */
const BYTE HID_ReportDescriptor[] = {
  HID_UsagePageVendor(0x00),
  HID_Usage(0x01),
  HID_Collection(HID_Application),
    // ---------- common global items ----------
    HID_LogicalMin(0),
    HID_LogicalMaxS(0xFF),
    HID_ReportSize(8),
    // ---------- input report ----------
    HID_ReportCount(64),
    HID_Usage(0x01),
    HID_Input(HID_Data | HID_Variable | HID_Absolute),
    // ---------- output report ----------
    HID_ReportCount(4),
    HID_Usage(0x01),
    HID_Output(HID_Data | HID_Variable | HID_Absolute),
  HID_EndCollection,
};

Which MCU are you using?
Keil's example code is almost same for any type of MCU, but there are minor differences.

Tsuneo

Hi

I'm using a custom board,but I should say when I program that board with provided HID example with no change, everything works fine. But when I program it with my own code, that problem shows up.

In addition, my MCU is AT91SAM7S256.

I will test my board with this revised report descriptor and tell you what happens.

Regards.

Hi

Thanks for schematics. I should say that my board is using bad mode of pull-up resistor for D+, but I have used a simple way to solve enumeration problem.
I power up my board with an additional 5v(for JTAG), and start debugging board. In this mode,USB is not enumerated yet. Then I attach USB cable from my board to PC and enumeration starts with no problem.
But this is not my problem for sure.
When I program my board with base HID example from USB library, there is no problem with anything. my board works both normally(attaching device to PC), or when I debug my board with ULINK. then there should not be any problem with my board.
But when I program board with my own USB codes(customized from those libraries), if I attach device to PC it says "USB device not recognized", but when I start debugging my board(then there are some delays between configuration steps when I break on breakpoints), my configuration of USB device proceeds several steps(not to a exact steps, once only till getting report descriptor, once till fully recognizing device).
Then I think there is a synchronization problem in my code that leads to this behavior.

In addition I tested my code using new report descriptor, but nothing changed.
EP0 is a 2 way control endpoint, is it possible that configuration packets via this endpoint are transferred incorrectly?

Regards

Hi

Sorry for late replay, I was on my weekend. :)

After working more on my device, I noticed what the problem was. It seems that my code itself had no problems but there are some problem with USBlyzer on my PC. Because after uninstalling it, my HID device is recognized with no problem.
But I currently have another problem that I'm working on it. I can send data to my HID usb device, but I cannot read anything from it. I don't think it that the problem comes from my PC side test code, but I need to investigate more.
But there is some more small questions if you have time for them too.. :)
1- Is it ok to send 2 packets of data both equal to wMaxPacketSize with no delay? I mean can I simply split my buffer which is bigger than wMaxPacketSize to smaller buffers and send then like this(it is pseudo-code):

Send_Buffer_To_Host(buf, len)
while (len > 0)
{
  tmplen = len > wMaxPacketSize? wMaxPacketSize : len
  USB_SendEP(0x81, tmplen of buf, tmplen)
  len -= tmplen
  buf += tmplen
}

I mean several calls for sending data will not cause any problem?
2-There are quite a lot unimplemented event callbacks in HID library. Is there any special one which is recommended to implement?
3-Should I make sure to protect my write and read function with SWI for interrupt protecting? Is there any other functions that is needed to protect too or not?

Regards

> It seems that my code itself had no problems but there are some problem with USBlyzer on my PC. Because after uninstalling it, my HID device is recognized with no problem.

Did you install two or more software sniffers on the PC?
Depending on the sniffers, it causes conflict among sniffers each other.



> 1- Is it ok to send 2 packets of data both equal to wMaxPacketSize with no delay?

As the interrupt endpoint doesn't have double buffer, the firmware has to wait until the first packet finishes to transfer to host, before it passes next packet to the endpoint.

For request/response pair over HID OUT/IN endpoint, typical code pattern is as follows.

The size of request / response affects the descriptors as follows.
request (4 bytes) - output report - OUT endpoint
response (128 bytes) - input report IN endpoint
On the report descriptor, the size of the input and output reports exactly match to the requirement.
On the OUT endpoint descriptor, set to equal or more size than the requirement - any value from 4 to 64 bytes will do. For IN endpoint, set it to 64 (maximum for full-speed). The input report is split into two 64 bytes packets.

usbdesc.c

/* HID Report Descriptor */
const BYTE HID_ReportDescriptor[] = {
  HID_UsagePageVendor(0x00),
  HID_Usage(0x01),
  HID_Collection(HID_Application),
    // ---------- common global items ----------
    HID_LogicalMin(0),
    HID_LogicalMaxS(0xFF),
    HID_ReportSize(8),
    // ---------- input report ----------
    HID_ReportCount(128),                                  // <------ set to 128 bytes
    HID_Usage(0x01),
    HID_Input(HID_Data | HID_Variable | HID_Absolute),
    // ---------- output report ----------
    HID_ReportCount(4),                                    // <------ set to 4 bytes
    HID_Usage(0x01),
    HID_Output(HID_Data | HID_Variable | HID_Absolute),
  HID_EndCollection,
};


const BYTE USB_ConfigDescriptor[] = {
  ...
  ...
/* Endpoint, HID Interrupt In */
  USB_ENDPOINT_DESC_SIZE,            /* bLength */
  USB_ENDPOINT_DESCRIPTOR_TYPE,      /* bDescriptorType */
  USB_ENDPOINT_IN(1),                /* bEndpointAddress */
  USB_ENDPOINT_TYPE_INTERRUPT,       /* bmAttributes */
  WBVAL(0x0040),                     /* wMaxPacketSize */    <------- set to 64 bytes
  0x20,          /* 32ms */          /* bInterval */
/* Endpoint, HID Interrupt Out */
  USB_ENDPOINT_DESC_SIZE,            /* bLength */
  USB_ENDPOINT_DESCRIPTOR_TYPE,      /* bDescriptorType */
  USB_ENDPOINT_OUT(2),                /* bEndpointAddress */
  USB_ENDPOINT_TYPE_INTERRUPT,       /* bmAttributes */
  WBVAL(0x0004),                     /* wMaxPacketSize */    <------- set to 4 - 64 bytes
  0x20,          /* 32ms */          /* bInterval */
  ...

Simple implementation is here.
- When output report comes from host, is it caught in EP2 interrupt
- EP2 ISR (Interrupt Service Routine) parses the request. As the result, an input report is generated on a buffer. The first packet of IN transfer is sent to the IN EP1 in this interrupt.
- When the transaction of the first packet finishes, EP1 ISR is called. In this ISR, the latter half of the input report is passed to the endpoint.

usbcfg.h
#define USB_EP_EVENT        0x0007    // enable EP0, 1, 2 interrupts

usbuser.c
BYTE request_buf[4];
BYTE response_buf[128];
BOOL send_next = FALSE;

void USB_EndPoint1 (DWORD event) {    // IN EP
  if ( send_next ) {
    send_next = FALSE;
    USB_WriteEP( 0x81, &response_buf[64], 64 );         // send the second packet
  }
}

void USB_EndPoint2 (DWORD event) {    // OUT EP
  DWORD byte_count;

  byte_count = USB_ReadEP( 0x02, request_buf );    // read output report
  //
  // parse the request here
  // and fill response_buf
  //
  USB_WriteEP( 0x81, response_buf, 64 );           // send the first packet
  send_next = TRUE;
}

void USB_EndPoint3 (DWORD event) {
// EP3 is not used
// Comment these lines
//  GetInReport();
//  USB_WriteEP(0x83, &InReport, sizeof(InReport));
}

In above code, USB_EndPoint2() is called twice, when both of the first and second transaction finishes. send_next flag distinguishes these calls.
This kind of flags and variables, which relate to USB communication, are initialized in USB_Configure_Event() - Set_Configuration request handler.

usbuser.c
#if USB_CONFIGURE_EVENT
void USB_Configure_Event (void) {
  if (USB_Configuration) {                  /* Check if USB is configured */

// For request / response exchange, the first input report is not required.
// Comment these lines
//    GetInReport();
//    USB_WriteEP(0x83, &InReport, sizeof(InReport));

//
// Instead other initialization is placed here
//
    send_next = FALSE;
  }
}
#endif

Tsuneo

Hi

Thanks for quick and great replies. :)

In above code, USB_EndPoint2() is called twice
Why it is called twice?
Shouldn't it get called only once when I receive data on EP2?

Is there any flag that shows a buffer in an IN endpoint has been sent to host(and host is received it)?

And regarding processing time, device has a really wide range of processing time, from a few milliseconds to even 1.5 mins, But I don't think it really makes problems for my application side, if this delay won't make any problem in MCU itself(for example these process delays will happen in ISR because of library code).

Regards

>> In above code, USB_EndPoint2() is called twice
> Why it is called twice?
> Shouldn't it get called only once when I receive data on EP2?

Auu, my bad ...
It's EP1 (IN endpoint), instead of EP2 (OUT endpoint)
The OUT EP ISR is called once, when the OUT endpoint receives the request from host.
The IN EP ISR is called twice, when the IN endpoint sends each packet to the host.



> Is there any flag that shows a buffer in an IN endpoint has been sent to host(and host is received it)?

These Bits on USB engine registers are available for polling, when interrupt is not enabled on the endpoint.

UDP_ISR (Interrupt Status Register) - EPxINT bit (IN and OUT endpoint)
or
UDP_CSRx (Endpoint Control and Status Register) - TXCOMP (IN endpoint), RX_DATA_BK0 (OUT endpoint)

Tsuneo

Hi Tsuneo

Thanks for your great replies. :)
I worked on my code for a lot and now I have no problem on sending and receiving small buffers(less than wMaxPacketSize).
But I should say that I were not able to send any report that is bigger than wMaxPacketSize.
Assume that I have set my INPUT and OUTPUT report size to 8 and report count to 128(so buffer is 128 bytes) and my wMaxPacketSize is 64.
When I try to send data from host to device,I need to send them in 128 byte buffers(and trying to send less than this much generates errors), but I only receive first 64 bytes in my device. Similarly, when I need to read 128 bytes from device(less than that much is not allowed), I can only send first 64 bytes from device to endpoint, then because host side has not received enough data, it goes into deadlock for receiving reminder of data that never happens.
Any idea how I can repair this problem?
In addition, the is a flag for INPUT and OUTPUT reports called 'Byte Stream'. is it good to set this flag if all my report data is byte aligned?

Regards

Hi

I should say That was able to send 128 Byte buffer (bigger than wMaxPacketSize) from host to device on my OUTPUT report, so no problem for this part anymore... :)
But my problem for INPUT report persists, and I cannot send data to host... :(

Regards

> When I try to send data from host to device,I need to send them in 128 byte buffers

Are you working on Windows?
Then, the buffer size to pass to ReadFile()/Writefile() is 129 bytes (1 + 128).
Report ID (1 byte) precedes before the 128 bytes body.

When the report descriptor on the device doesn't have any report ID,
- Windows app: default report ID (0) precedes.
- HID device: no report ID is attached.

Tsuneo