Lpc2000

I was trying to upload into flash from Philips Flash Utility software,
and it always complaints that the board coul not be connected.

I have tested the serial port with other harware, it works.
I have try all the baud rate available on the Flash Utility.
I make sure the BSL is on.

But...
I'm using a USB to serial convertor, could it be the problem?  E.g.
low voltage, ...