[FAQ] MCU-PLUS-SDK-AM243X: Can AM243x use OSPI PSRAM as a memory expansion?

Yes, AM243x OSPI can be connected to a PSRAM.

Below we explain motivation, and provide a summary of HW/SW changes required to add an AP Memory (APS6408L-OBM-BA) to AM243x EVM 

Motivation: Some applications require additional memory. While DDR, FLASH are options, sometimes they are not the correct fit. Some examples below:

DDR might not be a preferred solution due to: 

1. PCB layout & timing challenges
2. Cost

Flash might also not be good solution due to:

1. Less throughput (MB/s) than PSRAM 
2. Accessing flash memory devices is serial in nature.

Hardware modification: 

AM243x EVM + OSPI PSAM schematics:

PROC101E1_OSPI_SCH_AM243x.pdf

Note: Above schematic can be used as a reference. Currently this board is not sold in TI.com 

To enable OSPI PSRAM a high-speed switch was added to the board

High Speed Switch (S3DDR3812RUAR) uses OSPI_SW_SEL to select between OSPI Flash (low) and OSPI RAM (high). There is a 10K pull-down on OSPI_SW_SEL to default to OSPI FLASH.

IO Expander I2C is used to set OSPI_SW_SEL. Pin23 (20) corresponds to OSPI_SW_SEL.

Software modifications:

Modification of MCU+SDK, and an example application with a driver can be found at TI's Github Beyond SDK 

Beyond SDK:  GitHub - TexasInstruments/Beyond-SDK

AM243x OSPI PSAM example: Beyond-SDK/am243x/examples at main · TexasInstruments/Beyond-SDK · GitHub

Readme (Beyond-SDK/am243x/examples/ospi/ospi_psram_io/am243x-evm/r5fss0-0_nortos/Docs at main · TexasInstruments/Beyond-SDK · GitHub) explains how to patch MCU+SDK and gives a brief introduction on included files and how to build the project.

For running the application users can flash application or can use CCS JTAG to load *.out