11 years ago.

Hi,

FTDI chips does not enumerate as serial devices... If you want to use a FTDI chip, you need to filter the usb device by vid/pid instead of usb class.

A good starting point is to take a look at USBHostSerial.cpp:

/*virtual*/ void USBHostSerial::setVidPid(uint16_t vid, uint16_t pid)
{
    // we don't check VID/PID for Serial driver
}
 
/*virtual*/ bool USBHostSerial::parseInterface(uint8_t intf_nb, uint8_t intf_class, uint8_t intf_subclass, uint8_t intf_protocol) //Must return true if the interface should be parsed
{
    if ((serial_intf == -1) &&
        (intf_class == SERIAL_CLASS) &&
        (intf_subclass == 0x00) &&
        (intf_protocol == 0x00)) {
        serial_intf = intf_nb;
        return true;
    }
    return false;
}
 
/*virtual*/ bool USBHostSerial::useEndpoint(uint8_t intf_nb, ENDPOINT_TYPE type, ENDPOINT_DIRECTION dir) //Must return true if the endpoint will be used
{
    if (intf_nb == serial_intf) {
        if (type == BULK_ENDPOINT) {
            serial_device_found = true;
            return true;
        }
    }
    return false;
}

These three methods are automatically called when a usb device is connected. You can use the setVidPid method to find a ftdi chip. Then you don't have to check that "intf_class == SERIAL_CLASS" as it is not the case for these chips...

Cheers, Sam

11 years ago.

I have attempted to get this to work, but my USB knowlage is not vast,

can we have an example please.

Bizzarly though, the MCP2200 does work,

But I would also realy want to be able to controll some equipment with FTDI chips inside,

Thanks

Ceri

9 years, 7 months ago.

Samuel,

What do you mean when you say "FTDI chips does not enumerate as serial devices"?

I am considering purchasing an mbed LPC1768 board. My plan is to solder a USB female receptacle to the appropriate D+ and D- pins, add two 15k resistors, and program the board as USB host as indicated in http://mbed.org/handbook/USBHostSerial. Then, I would plug a second board to the USB female receptable. This second board is a USB device and has the FTDI chip shown in http://www.ftdichip.com/Products/ICs/FT232B.htm. Would I have any USB recognition problem with this set up?

9 years, 7 months ago.

Samuel says it quite clearly. USB devices send descriptors to the host, the device descriptors contains a "class". Classes can be for instance mass storage device, human interface device or serial device. Classes allow that a generic class driver is used for products from different manufacturers. Although the FTDI chip is a serial device, FTDI has decided not to enumerate it as a serial device. Therefore its class is not serial device but manufacturer defined. In such a case you should call a manufacturer driver. In such case the driver is defined by the vid/pid combination and possibly other parameters. So instead of testing for the device class you test for the vid/pid combination of your FTDI device. AFAIK the chip itself is a normal serial device so you won't need to change much else. Beware of the correct endpoint numbers though.

void USBHostSerial::setVidPid(uint16_t vid, uint16_t pid) {
   if (vid and pid are the corresponding values of my FTDI chip)
      call some method;
}

#define CHECK_INTERFACE(cls,subcls,proto) \
        (((cls == 0xFF)         && (subcls == 0xFF) && (proto == 0xFF)) /* QUALCOM CDC */  || \
         ((cls == SERIAL_CLASS) && (subcls == 0x00) && (proto == 0x00)) /* STANDARD CDC */ )

/*virtual*/ void USBHostSerial::setVidPid(uint16_t vid, uint16_t pid)
{
    // we don't check VID/PID for MSD driver
}

/*virtual*/ bool USBHostSerial::parseInterface(uint8_t intf_nb, uint8_t intf_class, uint8_t intf_subclass, uint8_t intf_protocol) //Must return true if the interface should be parsed
{
    if (!ports_found &&
        CHECK_INTERFACE(intf_class, intf_subclass, intf_protocol)) {
        port_intf = intf_nb;
        ports_found = true;
        return true;
    }
    return false;
}

/*virtual*/ bool USBHostSerial::useEndpoint(uint8_t intf_nb, ENDPOINT_TYPE type, ENDPOINT_DIRECTION dir) //Must return true if the endpoint will be used
{
    if (ports_found && (intf_nb == port_intf)) {
        if (type == BULK_ENDPOINT)
            return true;
    }
    return false;
}

class USBHostFTDISerial: public USBHostSerial
{ uint16_t _vid, _pid;
public:
  virtual void setVidPid(uint16_t vid, uint16_t pid) { _vid=vid;_pid=pid;}
  virtual bool parseInterface(uint8_t intf_nb, uint8_t intf_class, uint8_t intf_subclass, uint8_t intf_protocol)
    { /* test anything you like and return true on success
          eg. test _vid/_pid instead of class,subclass,proto but keep the other tests and settings */
    }
};