The LPC2138 of the ARMweb and the LPC1756 of the SuperPRO support a single 10
bit DAC.
(these details in the User manual for the repsective CPU)
First the pin select register has to be programmed for AOUT
in LPC2138
#define PINSEL1 *&HE002C004
PINSEL1 = (PINSEL1 and &HFFF3FFFF) or &H40000
in LPC1756
#define PINSEL1 *&H4002C004
PINSEL1 = (PINSEL1 and &HFFCFFFFF) or &H200000
Then you can write to the DAC register
#define DACR *&HE006C000 ' for 2138
#define DACR *&H4008C000 ' for 1756
DACR = value << 6
This will provide 700 uA of current and rates up to 1 Msample
In addition the LPC1756 has support for DMA and timer based loading.