Just some ideas:
(1) double check if you have the Pin P0.14 low during power-on or reset.
The bootloader will not start when the Pin is high and a valid
user-application is in flash. So tools like lpc21isp, the Philips ISP
tool or flash-magic can not connect (see for example
http://www.olimex.com/dev/images/lpc-h2129-sch.gif Jumper BSL).
(2) Check if the power-supply to the LPC (both 3,3 and 1,8V) and
RS232-transceiver is available (DMM) and stable(scope).
(3) Check if the XTAL is connected and oscillating with a scope.
(3) double check your RS232-transceiver circuit and do a
"loop-back"-test. This could be done like this:
- make sure the bootloader does not get started (P0.14 high) to keep
the LPC's bootloader for configuring the UART TX as output and driving
- if you have the option to disconnect the LPC from the
RS232-transceiver (MAX3232 or whatever is used on your board) with
jumpers or "solder-jumpers" disconnect at least the LPC TX-line from the
- Now that the LPC does not drive TX you can connect the two pins of the
RS232-transceiver on the logic-side (those connected to RX/TX of the
LPC) and test if characters you send with Hypterterm are send back and
shown in the Hyperterm Windows (I suggest to use the Bray Terminal for
If the test fails there might be a broken cable, wrong cable (maybe a
RX/TX crossed), broken connector or broken transceiver-IC.
(4) check if the LPC RX/TX Pins and the LPC itself are still working:
Since you can not access the bootloader to upload firmware to the LPC
flash you need an option to flash though JTAG (hopefully you have not
set the "magic protection value"). If you do not have any
hardware/software for this you can build a Wiggler and use OpenOCD or
H-JTAG with it. Than create a small application which configures the
TX-pin as GPIO output, the RX-pin as GPIO input and then reads the state
of the RX-Pin and sets the TX-Pin depending on the RX state in a loop.
Use Hyperterm/Bray-Terminal to send characters to the device. They
should be "echoed" back.
Hope this helps