On Wed, 5 May 2010 08:56:58 +0100, "N_Cook" put
> finger to keyboard and composed:
>
> >that 1K5 will have to go back in , It is the first point of recognition
for
>USB linking. Next to find why DISCON is permanently H.
>
> My understanding is that the pullup resistor on D+ signals to the host
> (your PC) that a USB device has been plugged in. The host then
> attempts to enumerate (ie identify) the device.
>
> If the device takes too long to go through its POST and initialisation
> routines, then the host may time out. In such cases the device may
> implement an active pullup which is disabled during its POST. When the
> device is ready, the pullup resistor is enabled, allowing enumeration
> to begin.
>
> AIUI, the normal state of DISCON# is high.
>
> See this EZ-USB Development Board (circuit on pages 5 & 6):
>formatting link
>
> I found this detailed document:
>
> The EZ-USB USB Integrated Circuit Technical Reference:
>formatting link
>
> It states that EZ-USB devices can power up in RAM-only mode, in which
> case the host downloads runtime code into the 8051 CPU's internal 8K
> RAM. During this time the device identifies itself as a "Default USB
> Device". After the code has been downloaded, the device disconnects
> and then reconnects, this time renumerating as the device defined
> within the downloaded code.
>
> Page 41 describes the EA (external access) pin. I think this may be
> the key to how the device behaves. The tech ref also talks about mask
> ROMed versions. Perhaps there is a way to force the EZ-USB chip into
> RAM-only mode??? If so, then this will remove any corrupt firmware
> from the equation. You could then use UVCView to see how the device
> enumerates under these circumstances.
>
> You could also disconnect the serial EEPROM, if any. The EEPROM would
> contain Product and Vendor IDs for the manufacturer of the mixer. If
> the EEPROM is absent, then the EZ-USB chip will ID with the PID and
> VID of 0x0547 (Cypress Semiconductor) and 0x2131 (EZ-USB),
> respectively.
>
> - Franc Zabkar
> --
> Please remove one 'i' from my address when replying by email.
I got back to this today. Saved to disc the existing (corrupted ?) data in the serial EEPROM and cut the SDA line to the Ez-usb chip. The EZbus mixer is no longer "Becoming Ezbus" and a blank screen. But windows recognises a USB device connected and by UVCView/USB view the USB is working up to the USB chip , reading
---===>Device Information Device Bus Speed: Full Device Address: 0x00 Open Pipes: 0
*!*ERROR: No open pipes!
===>Device Descriptor This is a Vendor Specific Device bDeviceSubClass: 0xFF bDeviceProtocol: 0xFF bMaxPacketSize0: 0x40 = (64) Bytes idVendor: 0x0547idProduct:
0x2131 bcdDevice: 0x0004 iManufacturer: 0x00 iProduct: 0x00 iSerialNumber: 0x00 bNumConfigurations: 0x01
ie Cypress VID/PID
Where to now? presumably forcing a pipe somehow