Hi I’m playing with the usb serial port code from FreeRTOS V5.0.2 / lwIP_Demo_Rowley_ARM7 and I think there’s a couple of things in the descriptors.h which might be improved. The serial port can be made to work with linux if you change the value of the interface protocol (the comment is bInterfaceProtocol) in the config descriptor (pxConfigDescriptor) to something valid.  It has a value of 0, which I don’t think the spec allows.  By making it 1, linux will work.  In ubuntu, my device is now available as a serial port named /dev/ttyACM0 .  Windows is unaffected, except that you might have to reinstall the driver if you’ve used the old value. That is, change the value in descriptors.h line 117 from: 0x00  to 0x01 . Also, I think the values for the vendor id and product id are confusing.  The atmel USB vendor id is 0x03EB.  In descriptors.h and the FreeRTOSCDC.inf for windows this value has the wrong byte order.  This will work fine for the demo, but its confusing as an example (if you did mean to use the atmel vendor id). Thanks, Mick D -– C:/FreeRTOSV5.0.2-orig/Demo/lwIP_Demo_Rowley_ARM7/USB/descriptors.h    Fri May 30 16:27:00 2008 +++ C:/FreeRTOSV5.0.2/Demo/lwIP_Demo_Rowley_ARM7/USB/descriptors.h    Wed Jun 25 11:47:19 2008 @@ -114,8 +114,8 @@      0x00,                                /* bDeviceSubclass:        */      0x00,                                /* bDeviceProtocol:        */      0x08,                                /* bMaxPacketSize0        */ –    0x03, 0xEB,                            /* idVendorL            */ –    0x20, 0x09,                            /* idProductL            */ +    0xEB, 0x03,                            /* idVendorL            */ +    0x09, 0x20,                            /* idProductL            */      0x10, 0x01,                            /* bcdDeviceL            */      usbMANUFACTURER_STRING,              /* iManufacturer        */      usbPRODUCT_STRING,                    /* iProduct                */ @@ -148,7 +148,7 @@      0x01,                /* bNumEndpoints                        */      0x02,                /* bInterfaceClass: Comm Interface Class */      0x02,                /* bInterfaceSubclass: Abstract Control Model*/ –    0x00,                /* bInterfaceProtocol                    */ +    0x01,                /* bInterfaceProtocol                    */      usbINTERFACE_STRING,/* iInterface                            */      /* Header Functional Descriptor                                */

Excellent information – thanks.  I’m updating the SVN repository now. Regards

FYI, by making this change device will not be seen as a usb-serial device so it is not possible to use serial console programs like minicom. Instead one can change bmCapabilities field in call management functional descriptor to 0x01(originally it is 0x00). So it will be possible to use serial emulation programs with the device, at least this is what I’m doing. Regards, Caglar

So you are saying its best to leave bInterfaceProtocol as 0, and change bInterfaceProtocol to 1 instead.  Can somebody verify that this will work under Linux too? Regards.

Both yes and no. If you were meant to say bmCapabilities in the place second of bInterfaceProtocol in your second, then yes. I’ve tested this on SUSE and it’s working with usbserial module. To test driver someone can try these as root after plugging device. $modprobe usbserial vendor=0xeb03 product=0x0920 $minicom -s then write /dev/ttyUSB0 under Serial Port Setup->Serial Device and click ESC twice. It should work. Regards, Caglar

I’ve tried this and can’t get it to work, for ubuntu hardy at least.  If I understand you correctly, then compared to the freertos source, there’s only 1 change. bmCapabilities = 0x01 for the call management interface in descriptors.h .  My patch is below.  /dev/ttyUSB0 shows up after I use the modprobe command, but minicom seems to hang when sending to it, even running as root. I tried minicom with my previous patch, and it worked with /dev/ACM0 ok. Thanks -– FreeRTOSV5.0.2-orig/Demo/lwIP_Demo_Rowley_ARM7/USB/descriptors.h    2008-05-30 16:27:00 +0800 +++ FreeRTOSV5.0.2/Demo/lwIP_Demo_Rowley_ARM7/USB/descriptors.h    2008-06-26 14:11:31 +0800 @@ -175,7 +175,7 @@      0x05,                /* bFunctionLength                        */      0x24,                /* bDescriptor type: CS_INTERFACE        */      0x01,                /* bDescriptor subtype: Call Management Func*/ –    0x00,                /* bmCapabilities: D1 + D0                */ +    0x01,                /* bmCapabilities: D1 + D0                */      0x01,                /* bDataInterface: Data Class Interface 1*/      /* CDC Control – Endpoint 3 descriptor

You are right, your solution is working with minicom also. Both methods are working for me. Regards, Caglar

I have used LPCUSB on a NXP lpc2368 and it sets both bInterfaceProtocol and bmCapabilities to a 1. It works fine for me in Ubuntu using minicom. // device descriptor     0x12,     DESC_DEVICE,     LE_WORD(0x0101),            // bcdUSB     0x02,                        // bDeviceClass     0x00,                        // bDeviceSubClass     0x00,                        // bDeviceProtocol     MAX_PACKET_SIZE0,            // bMaxPacketSize     LE_WORD(0xFFFF),            // idVendor     LE_WORD(0x0005),            // idProduct     LE_WORD(0x0100),            // bcdDevice     0x01,                        // iManufacturer     0x02,                        // iProduct     0x03,                        // iSerialNumber     0x01,                        // bNumConfigurations // configuration descriptor     0x09,     DESC_CONFIGURATION,     LE_WORD(67),                // wTotalLength     0x02,                        // bNumInterfaces     0x01,                        // bConfigurationValue     0x00,                        // iConfiguration     0xC0,                        // bmAttributes     0x32,                        // bMaxPower // control class interface     0x09,     DESC_INTERFACE,     0x00,                        // bInterfaceNumber     0x00,                        // bAlternateSetting     0x01,                        // bNumEndPoints     0x02,                        // bInterfaceClass     0x02,                        // bInterfaceSubClass     0x01,                        // bInterfaceProtocol, linux requires value of 1 for the cdc_acm module     0x00,                        // iInterface // header functional descriptor     0x05,     CS_INTERFACE,     0x00,     LE_WORD(0x0110), // call management functional descriptor     0x05,     CS_INTERFACE,     0x01,     0x01,                        // bmCapabilities = device handles call management     0x01,                        // bDataInterface // ACM functional descriptor     0x04,     CS_INTERFACE,     0x02,     0x02,                        // bmCapabilities // union functional descriptor     0x05,     CS_INTERFACE,     0x06,     0x00,                        // bMasterInterface     0x01,                        // bSlaveInterface0 // notification EP     0x07,     DESC_ENDPOINT,     INT_IN_EP,                    // bEndpointAddress     0x03,                        // bmAttributes = intr     LE_WORD(8),                    // wMaxPacketSize     0x0A,                        // bInterval // data class interface descriptor     0x09,     DESC_INTERFACE,     0x01,                        // bInterfaceNumber     0x00,                        // bAlternateSetting     0x02,                        // bNumEndPoints     0x0A,                        // bInterfaceClass = data     0x00,                        // bInterfaceSubClass     0x00,                        // bInterfaceProtocol     0x00,                        // iInterface // data EP OUT     0x07,     DESC_ENDPOINT,     BULK_OUT_EP,                // bEndpointAddress     0x02,                        // bmAttributes = bulk     LE_WORD(MAX_PACKET_SIZE),    // wMaxPacketSize     0x00,                        // bInterval // data EP in     0x07,     DESC_ENDPOINT,     BULK_IN_EP,                    // bEndpointAddress     0x02,                        // bmAttributes = bulk     LE_WORD(MAX_PACKET_SIZE),    // wMaxPacketSize     0x00,                        // bInterval

Sorry to re-open an old discussion but I see that the bInterfaceProtocol is back to 0x00 since revision 426 as evidenced here: http://freertos.svn.sourceforge.net/viewvc/freertos/trunk/Demo/lwIP_Demo_Rowley_ARM7/USB/descriptors.h?r1=400&r2=426 Is there a reason for that? I am asking because without that I haven’t been able to get USB working from Linux (I am using Ubuntu Hardy) without setting bInterfacceProtocol to 1. Thanks.

Unfortunately I don’t have a Linux machine to test on, and I get conflicting reports from users on how the descriptors should be configured.  Its nothing more than that. Regards.