Isochronus Usb Device in LPC2468

Hi Techies, Presently we are working on LPC2468 OEM Board for isochronus transfer in USB Device.

Can anybody exaplains the hardware behaviour(Registers use) with isochronus data transfer for IN and OUT in LPC2468.

Our quiries are
1.When we configure the Endpoints (IN or OUT) as Isochronus then how can we know that which Endpoint is received/transmition (was success for IN)the data?

User manual is explaining that we get the FRAME interrupt for isochronus Endpoint, but after getting the frame interrupt what we have to do?

2. What is the use of Start of Frame (11 bits) value? How can we use it?What information it contains?

Parents
  • LPC2468 has both of USB device and host function.
    You seem asking about the USB device side, not for the host.

    The USB device function on LPC2468 is almost same as LPC214x and LPC236x-237x. Then, these examples on the KEIL web pages show the isoc endpoint (EP) handling.

    LPC2148 USB Audio Device Example
    http://www.keil.com/download/docs/308.asp

    LPC2368 / LPC2378 USB Audio Device Example
    http://www.keil.com/download/docs/334.asp

    In the USB 1.0/1.1 spec, the bInterval of isoc EP is fixed to 1ms, a packet per single USB frame of full-speed (FS). Though the USB 2.0 spec allows other setting for bInterval, FS isoc EP is usually driven in 1ms interval, because of this historical reason. The isoc EPs on LPC family is designed following this 1ms custom.



    "1. how can we know that which Endpoint is received/transmition (was success for IN)the data? ... after getting the frame interrupt what we have to do?"

    Isoc EP doesn't directly generate any interrupt on this MCU.
    You have to check each isoc endpoint in the SOF (Start Of FRAME) interrupt service routine (ISR).

    For OUT EP, check Receive Packet Length register (USBRxPLen), PKT_RDY, DV and PKT_LNGTH fields. If it is valid data, read out it. If it isn't, drop the packet.

    For IN EP, just send the next packet.
    There is no flag which shows success on the last packet. The isoc protocol doesn't care if the packet may drop.



    "2. What is the use of Start of Frame (11 bits) value? How can we use it?What information it contains?"

    It's the frame number, attached to the SOF packet.
    Each SOF packet has this frame number, incremented by one on each frame.
    Tracking this number on each SOF (FRAME) interrupt, drop of SOF reception is detected.

    Tsuneo

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