PCB design using LPC11U24

23 May 2012

I am trying to design a PCB using the LPC11U24 processor. I used the yellow mbed to prototype with and am now trying to move to my own PCB. I am having difficulty trying to understand how the magic chip programs the chip. It seems it doesn't use regular JTAG interface, but instead uses its own ISP - it uses TXD and RXD instead of TDI and TDO, but it does use TCK for the clock. After looking at the schematic and the datasheet/user guide for some time I figured out that to put the device into ISP mode, pin 6 needs to be low (this is handled by the magic chip). The magic chip is also using pin 6 for TGT_JTAG_IRQ, but the user guide states that this is just a GPIO. I am unsure of how the compiler is handling this interrupt request and I assume it is in the mbed library, but I'm not sure how to find this information. Does anyone have any suggestions?


Wes Petree

17 Jul 2012

Wes, you should check out my post on this http://mbed.org/forum/mbed/topic/3641/. I got this up and running and you can treat this chip like a usb drive and update the firmware without an interface. Next revision will change from the spec'd resonator to an acutal crystal. Other than that the design works great.