ISP via USB MSC on the LPC11U24
I am having problems getting the ISP USB Flash programming feature to work with a new design using an LPC11U24 device. My past experience was with an LPC1343. On this past design we simply hard wired PIO0_1 on the design to ground, powered on the unit to reset the product, and the device would enumerate in Windows as a Mass Storage Class Device observable on the PC. Programming the part was as easy as dropping the programming file into the MSC Device just like it was a USB Thumb drive. Normal operation from the design code occurred by removing the jumper and resetting the device.
I cannot duplicate this with the new design and here is what I have done with no success:
1. Wired PIO0_1 to ground (Necessary to invoke ISP on Reset)
2. Wired PIO0_3 to Vdd (Necessary to select USB ISP method)
3. 1.5K pullup on USB_DP wired active and not through a soft connect.
3. Plug in USB cable to Windows XP laptop
4. Turn on Power and Reset the Product
I can see the host try to enumerate the device but always get a USB unrecognized error. In device manager, the product is listed as USB Unknown. I have tried holding off the the USB_DP pull up after several seconds from reset with no change to the symptom.
1. Is there anything wrong with the setup described above?
2. Is it necessary to delay the USB_DP pull up activation after RESET?
3. The documentation advises that the IRC oscillator is used during boot and I assume this means during the ISP sequence. I am using a 16Mhz crystal for the design and in the previous design I was using 12Mhz. The latter frequency is common for USB clock synchronization. Is it possible that the ISP over USB requires a 12Mhz crystal and does not use the IRC due to precision problems?
I pulled the 16Mhz crystal and tied the XTAL input to ground and XTAL output floating in case the external crystal was causing noise to assure that the IRC was not disturbed. No change to the symptoms.
Any help would be greatly appreciated.