Posted on October 03, 2012 at 17:06
The CDC example of STM32_USB-Host-Device_Lib_V2.1.0 doesn't implemment handler of SET_CONTROL_LINE_STATE and SEND_BREAK.
Here is an outline of implementation.
1) Descriptors
Enable Send_Break at bmCapabilities field of ACM Functional Descriptors
STM32_USB-Host-Device_Lib_V2.1.0\Libraries\STM32_USB_Device_Library\Class\cdc\src\usbd_cdc_core.c
__ALIGN_BEGIN uint8_t usbd_cdc_CfgDesc[USB_CDC_CONFIG_DESC_SIZ] __ALIGN_END =
{
...
...
/*ACM Functional Descriptor*/
0x04, /* bFunctionLength */
0x24, /* bDescriptorType: CS_INTERFACE */
0x02, /* bDescriptorSubtype: Abstract Control Management desc */
0x02, /* bmCapabilities */ // <---- 0x06 (D2:Send_Break
// D1:Set/Get_Line_Coding,
// Set_Control_Line_State,
// Serial_State
...
...
__ALIGN_BEGIN uint8_t usbd_cdc_OtherCfgDesc[USB_CDC_CONFIG_DESC_SIZ] __ALIGN_END =
{
...
...
/*ACM Functional Descriptor*/
0x04, /* bFunctionLength */
0x24, /* bDescriptorType: CS_INTERFACE */
0x02, /* bDescriptorSubtype: Abstract Control Management desc */
0x02, /* bmCapabilities */ // <---- 0x06 (D2:Send_Break
// D1:Set/Get_Line_Coding,
// Set_Control_Line_State,
// Serial_State
2) CDC device class library
Modify usbd_cdc_Setup(), so that ''No Data request'' passes SETUP packet, instead of NULL.
STM32_USB-Host-Device_Lib_V2.1.0\Libraries\STM32_USB_Device_Library\Class\cdc\src\usbd_cdc_core.c
static uint8_t usbd_cdc_Setup (void *pdev,
USB_SETUP_REQ *req)
{
...
switch (req->bmRequest & USB_REQ_TYPE_MASK)
{
/* CDC Class Requests -------------------------------*/
case USB_REQ_TYPE_CLASS :
/* Check if the request is a data setup packet */
if (req->wLength)
{
...
...
}
else /* No Data request */
{
/* Transfer the command to the interface layer */
// APP_FOPS.pIf_Ctrl(req->bRequest, NULL, 0); // <---- this line is modified
APP_FOPS.pIf_Ctrl(req->bRequest, (uint8_t*)req, 0); // pass SETUP packet
}
return USBD_OK;
3) CDC device example
On the VCP_Ctrl() function, fill blank ''case SET_CONTROL_LINE_STATE'' and ''case SEND_BREAK''
STM32_USB-Host-Device_Lib_V2.1.0\Project\USB_Device_Examples\VCP\src\usbd_cdc_vcp.c
#include ''usb_core.h'' // to refer USB_SETUP_REQ structure // <---- add this line
#define CDC_RTS_MASK 0x02
#define CDC_DTR_MASK 0x01
static uint16_t VCP_Ctrl (uint32_t Cmd, uint8_t* Buf, uint32_t Len)
{
USB_SETUP_REQ * req = (USB_SETUP_REQ *)Buf; // for No Data request // <---- add this line
switch (Cmd)
{
...
case SET_CONTROL_LINE_STATE:
/* Not needed for this driver */
if (req->wValue & CDC_RTS_MASK) {
//
// host set RTS to '1' Set RTS port to '1', here
//
} else {
//
// host reset RTS to '0' Reset RTS port to '0', here
//
}
if (req->wValue & CDC_DTR_MASK) {
//
// host set DTR to '1'
//
} else {
//
// host reset DTR to '0'
//
}
break;
case SEND_BREAK:
/* Not needed for this driver */
// req->wValue holds the duration of break in milisecond.
// If req->wValue contains a value of FFFFh,
// then the device will send a break until another SendBreak request is received
// with the req->wValue of 0000h
break;
4) Windows bug
Lastly, Windows CDC driver, usbser.sys, has a bug on RTS signaling.
- RTS changes on the device side, when host puts DTR (even the same value of DTR will do)
Tsuneo
