Writing and Reading SDRAM with OMAP-L138

Joe Tijerina said:

I'm working with a omap L138 eXperimenter kit and need to write data samples to external SDRAM from the ARM and then have the uPP dma transfer those samples to an external peripheral.

Can the ARM write to external memory? If so, can you point me to a guide or example on how to do this?  (I have very little experience working with ARM GPPs.)

Yes, the ARM9 inside the OMAP-L138 can access external memory through either the DDR2/mDDR memory interface or the EMIFA memory interface.  On the OMAP-L138 Experimenter's kit, DRAM should be available on the DDR2/mDDR memory interface.  Table 3-3 of the OMAP-L138 datasheet indicates the address the DDR2/mDDR memory interface resides in the ARM memory map, which is 0xC0000000 - 0xDFFFFFFF.

Incidently, this same address range is available by the DSP, if you would rather use the DSP to access memory.

The Linux Platform Support Package uses the ARM to boot Linux and this uses the DRAM on the DDR2/mDDR memory interface.

Joe Tijerina said:

Or would I be better off transfering the data samples to the DSP and have the DSP write to ext SDRAM instead? Please advice.

I would say this depends on your application and how you want to process the data.  Either will work.